Documentation

Java Rules

java_binary

java_binary(name, deps, srcs, data, resources, args, classpath_resources, compatible_with, create_executable, deploy_manifest_lines, deprecation, distribs, features, javacopts, jvm_flags, launcher, licenses, main_class, output_licenses, plugins, resource_jars, resource_strip_prefix, restricted_to, runtime_deps, stamp, tags, testonly, use_testrunner, visibility)

Builds a Java archive ("jar file"), plus a wrapper shell script with the same name as the rule. The wrapper shell script uses a classpath that includes, among other things, a jar file for each library on which the binary depends.

The wrapper script accepts several unique flags. Refer to //src/main/java/com/google/devtools/build/lib/bazel/rules/java/java_stub_template.txt for a list of configurable flags and environment variables accepted by the wrapper.

Implicit output targets

  • name.jar: A Java archive, containing the class files and other resources corresponding to the binary's direct dependencies.
  • name-src.jar: An archive containing the sources ("source jar").
  • name_deploy.jar: A Java archive suitable for deployment (only built if explicitly requested).

    Building the <name>_deploy.jar target for your rule creates a self-contained jar file with a manifest that allows it to be run with the java -jar command or with the wrapper script's --singlejar option. Using the wrapper script is preferred to java -jar because it also passes the JVM flags and the options to load native libraries.

    The deploy jar contains all the classes that would be found by a classloader that searched the classpath from the binary's wrapper script from beginning to end. It also contains the native libraries needed for dependencies. These are automatically loaded into the JVM at runtime.

    If your target specifies a launcher attribute, then instead of being a normal JAR file, the _deploy.jar will be a native binary. This will contain the launcher plus any native (C++) dependencies of your rule, all linked into a static binary. The actual jar file's bytes will be appended to that native binary, creating a single binary blob containing both the executable and the Java code. You can execute the resulting jar file directly like you would execute any native binary.

  • name_deploy-src.jar: An archive containing the sources collected from the transitive closure of the target. These will match the classes in the deploy.jar except where jars have no matching source jar.

A deps attribute is not allowed in a java_binary rule without srcs; such a rule requires a main_class provided by runtime_deps.

The following code snippet illustrates a common mistake:

java_binary(
    name = "DontDoThis",
    srcs = [
        ...,
        "GeneratedJavaFile.java",  # a generated .java file
    ],
    deps = [":generating_rule",],  # rule that generates that file
)

Do this instead:

java_binary(
    name = "DoThisInstead",
    srcs = [
        ...,
        ":generating_rule",
    ],
)

Arguments

Attributes
name

Name; required

A unique name for this rule.


It is good practice to use the name of the source file that is the main entry point of the application (minus the extension). For example, if your entry point is called Main.java, then your name could be Main.
deps

List of labels; optional

The list of other libraries to be linked in to the target. See general comments about deps at Attributes common to all build rules .
srcs

List of labels; optional

The list of source files that are processed to create the target. This attribute is almost always required; see exceptions below.

Source files of type .java are compiled. In case of generated .java files it is generally advisable to put the generating rule's name here instead of the name of the file itself. This not only improves readability but makes the rule more resilient to future changes: if the generating rule generates different files in the future, you only need to fix one place: the outs of the generating rule. You should not list the generating rule in deps because it is a no-op.

Source files of type .srcjar are unpacked and compiled. (This is useful if you need to generate a set of .java files with a genrule.)

Rules: if the rule (typically genrule or filegroup) generates any of the files listed above, they will be used the same way as described for source files.

This argument is almost always required, except if a main_class attribute specifies a class on the runtime classpath or you specify the runtime_deps argument.

resources

List of labels; optional

A list of data files to include in a Java jar.

If resources are specified, they will be bundled in the jar along with the usual .class files produced by compilation. The location of the resources inside of the jar file is determined by the project structure. Bazel first looks for Maven's standard directory layout, (a "src" directory followed by a "resources" directory grandchild). If that is not found, Bazel then looks for the topmost directory named "java" or "javatests" (so, for example, if a resource is at <workspace root>/x/java/y/java/z, Bazel will use the path y/java/z. This heuristic cannot be overridden.

Resources may be source files or generated files.

classpath_resources

List of labels; optional

DO NOT USE THIS OPTION UNLESS THERE IS NO OTHER WAY)

A list of resources that must be located at the root of the java tree. This attribute's only purpose is to support third-party libraries that require that their resources be found on the classpath as exactly "myconfig.xml". It is only allowed on binaries and not libraries, due to the danger of namespace conflicts.

create_executable

Boolean; optional; nonconfigurable; default is 1

Whether the binary is executable. Non-executable binaries collect transitive runtime Java dependencies into a deploy jar, but cannot be executed directly. No wrapper script is created if this attribute is set. It is an error to set this to 0 if the launcher or main_class attributes are set.
deploy_manifest_lines

List of strings; optional

A list of lines to add to the META-INF/manifest.mf file generated for the *_deploy.jar target. The contents of this attribute are not subject to "Make variable" substitution.
javacopts

List of strings; optional

Extra compiler options for this library. Subject to "Make variable" substitution and Bourne shell tokenization.

These compiler options are passed to javac after the global compiler options.

jvm_flags

List of strings; optional

A list of flags to embed in the wrapper script generated for running this binary. Subject to $(location) and "Make variable" substitution, and Bourne shell tokenization.

The wrapper script for a Java binary includes a CLASSPATH definition (to find all the dependent jars) and invokes the right Java interpreter. The command line generated by the wrapper script includes the name of the main class followed by a "$@" so you can pass along other arguments after the classname. However, arguments intended for parsing by the JVM must be specified before the classname on the command line. The contents of jvm_flags are added to the wrapper script before the classname is listed.

Note that this attribute has no effect on *_deploy.jar outputs.

launcher

Label; optional

Specify a binary that will be used to run your Java program instead of the normal bin/java program included with the JDK. The target must be a cc_binary. Any cc_binary that implements the Java Invocation API can be specified as a value for this attribute.

The special value //tools/jdk:no_launcher indicates that you want to use the normal JDK launcher (bin/java or java.exe) as the value for this attribute. This is the default.

The related --java_launcher Bazel flag affects only those java_binary and java_test targets that have not specified a launcher attribute.

Note that your native (C++, SWIG, JNI) dependencies will be built differently depending on whether you are using the JDK launcher or another launcher:

  • If you are using the normal JDK launcher (the default), native dependencies are built as a shared library named {name}_nativedeps.so, where {name} is the name attribute of this java_binary rule. Unused code is not removed by the linker in this configuration.
  • If you are using any other launcher, native (C++) dependencies are statically linked into a binary named {name}_nativedeps, where {name} is the name attribute of this java_binary rule. In this case, the linker will remove any code it thinks is unused from the resulting binary, which means any C++ code accessed only via JNI may not be linked in unless that cc_library target specifies alwayslink = 1.

When using any launcher other than the default JDK launcher, the format of the *_deploy.jar output changes. See the main java_binary docs for details.

main_class

String; optional

Name of class with main() method to use as entry point. If a rule uses this option, it does not need a srcs=[...] list. Thus, with this attribute one can make an executable from a Java library that already contains one or more main() methods.

The value of this attribute is a class name, not a source file. The class must be available at runtime: it may be compiled by this rule (from srcs) or provided by direct or transitive dependencies (through runtime_deps or deps). If the class is unavailable, the binary will fail at runtime; there is no build-time check.

plugins

List of labels; optional

Java compiler plugins to run at compile-time. Every java_plugin specified in this attribute will be run whenever this rule is built. A library may also inherit plugins from dependencies that use exported_plugins. Resources generated by the plugin will be included in the resulting jar of this rule.
resource_jars

List of labels; optional

Set of archives containing Java resources.

If specified, the contents of these jars are merged into the output jar.

resource_strip_prefix

String; optional

The path prefix to strip from Java resources.

If specified, this path prefix is stripped from every file in the resources attribute. It is an error for a resource file not to be under this directory. If not specified (the default), the path of resource file is determined according to the same logic as the Java package of source files. For example, a source file at stuff/java/foo/bar/a.txt will be located at foo/bar/a.txt.

runtime_deps

List of labels; optional

Libraries to make available to the final binary or test at runtime only. Like ordinary deps, these will appear on the runtime classpath, but unlike them, not on the compile-time classpath. Dependencies needed only at runtime should be listed here. Dependency-analysis tools should ignore targets that appear in both runtime_deps and deps.
stamp

Integer; optional; default is 0

Enable link stamping. Whether to encode build information into the binary. Possible values:
  • stamp = 1: Stamp the build information into the binary. Stamped binaries are only rebuilt when their dependencies change. Use this if there are tests that depend on the build information.
  • stamp = 0: Always replace build information by constant values. This gives good build result caching.
  • stamp = -1: Embedding of build information is controlled by the --[no]stamp flag.
use_testrunner

Boolean; optional; default is 1

Use the test runner (by default com.google.testing.junit.runner.BazelTestRunner) class as the main entry point for a Java program, and provide the test class to the test runner as a value of bazel.test_suite system property. You can use this to override the default behavior, which is to use test runner for java_test rules, and not use it for java_binary rules. It is unlikely you will want to do this. One use is for AllTest rules that are invoked by another rule (to set up a database before running the tests, for example). The AllTest rule must be declared as a java_binary, but should still use the test runner as its main entry point. The name of a test runner class can be overriden with main_class attribute.

java_import

java_import(name, deps, data, compatible_with, constraints, deprecation, distribs, exports, features, jars, licenses, neverlink, proguard_specs, restricted_to, runtime_deps, srcjar, tags, testonly, visibility)

This rule allows the use of precompiled .jar files as libraries for java_library and java_binary rules.

Examples

    java_import(
        name = "maven_model",
        jars = [
            "maven_model/maven-aether-provider-3.2.3.jar",
            "maven_model/maven-model-3.2.3.jar",
            "maven_model/maven-model-builder-3.2.3.jar",
        ],
    )

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of other libraries to be linked in to the target. See java_library.deps.
constraints

List of strings; optional; nonconfigurable

Extra constraints imposed on this rule as a Java library.
exports

List of labels; optional

Targets to make available to users of this rule. See java_library.exports.
jars

List of labels; required

The list of JAR files provided to Java targets that depend on this target.

Boolean; optional; default is 0

Only use this library for compilation and not at runtime. Useful if the library will be provided by the runtime environment during execution. Examples of libraries like this are IDE APIs for IDE plug-ins or tools.jar for anything running on a standard JDK.
proguard_specs

List of labels; optional

Files to be used as Proguard specification. These will describe the set of specifications to be used by Proguard. If specified, they will be added to any android_binary target depending on this library. The files included here must only have idempotent rules, namely -dontnote, -dontwarn, assumenosideeffects, and rules that start with -keep. Other options can only appear in android_binary's proguard_specs, to ensure non-tautological merges.
runtime_deps

List of labels; optional

Libraries to make available to the final binary or test at runtime only. See java_library.runtime_deps.
srcjar

Label; optional

A JAR file that contains source code for the compiled JAR files.

java_library

java_library(name, deps, srcs, data, resources, compatible_with, deprecation, distribs, exported_plugins, exports, features, javacopts, licenses, neverlink, plugins, proguard_specs, resource_jars, resource_strip_prefix, restricted_to, runtime_deps, tags, testonly, visibility)

This rule compiles and links sources into a .jar file.

Implicit output targets

  • libname.jar: A Java archive containing the class files.
  • libname-src.jar: An archive containing the sources ("source jar").

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of libraries to link into this library. See general comments about deps at Attributes common to all build rules .

The jars built by java_library rules listed in deps will be on the compile-time classpath of this rule. Furthermore the transitive closure of their deps, runtime_deps and exports will be on the runtime classpath.

By contrast, targets in the data attribute are included in the runfiles but on neither the compile-time nor runtime classpath.

srcs

List of labels; optional

The list of source files that are processed to create the target. This attribute is almost always required; see exceptions below.

Source files of type .java are compiled. In case of generated .java files it is generally advisable to put the generating rule's name here instead of the name of the file itself. This not only improves readability but makes the rule more resilient to future changes: if the generating rule generates different files in the future, you only need to fix one place: the outs of the generating rule. You should not list the generating rule in deps because it is a no-op.

Source files of type .srcjar are unpacked and compiled. (This is useful if you need to generate a set of .java files with a genrule.)

Rules: if the rule (typically genrule or filegroup) generates any of the files listed above, they will be used the same way as described for source files.

This argument is almost always required, except if a main_class attribute specifies a class on the runtime classpath or you specify the runtime_deps argument.

data

List of labels; optional

The list of files needed by this library at runtime. See general comments about data at Attributes common to all build rules .

When building a java_library, Bazel doesn't put these files anywhere; if the data files are generated files then Bazel generates them. When building a test that depends on this java_library Bazel copies or links the data files into the runfiles area.

resources

List of labels; optional

A list of data files to include in a Java jar.

If resources are specified, they will be bundled in the jar along with the usual .class files produced by compilation. The location of the resources inside of the jar file is determined by the project structure. Bazel first looks for Maven's standard directory layout, (a "src" directory followed by a "resources" directory grandchild). If that is not found, Bazel then looks for the topmost directory named "java" or "javatests" (so, for example, if a resource is at <workspace root>/x/java/y/java/z, Bazel will use the path y/java/z. This heuristic cannot be overridden.

Resources may be source files or generated files.

exported_plugins

List of labels; optional

The list of java_plugins (e.g. annotation processors) to export to libraries that directly depend on this library.

The specified list of java_plugins will be applied to any library which directly depends on this library, just as if that library had explicitly declared these labels in plugins.

exports

List of labels; optional

Exported libraries.

Listing rules here will make them available to parent rules, as if the parents explicitly depended on these rules. This is not true for regular (non-exported) deps.

Summary: a rule X can access the code in Y if there exists a dependency path between them that begins with a deps edge followed by zero or more exports edges. Let's see some examples to illustrate this.

Assume A depends on B and B depends on C. In this case C is a transitive dependency of A, so changing C's sources and rebuilding A will correctly rebuild everything. However A will not be able to use classes in C. To allow that, either A has to declare C in its deps, or B can make it easier for A (and anything that may depend on A) by declaring C in its (B's) exports attribute.

The closure of exported libraries is available to all direct parent rules. Take a slightly different example: A depends on B, B depends on C and D, and also exports C but not D. Now A has access to C but not to D. Now, if C and D exported some libraries, C' and D' respectively, A could only access C' but not D'.

Important: an exported rule is not a regular dependency. Sticking to the previous example, if B exports C and wants to also use C, it has to also list it in its own deps.

javacopts

List of strings; optional

Extra compiler options for this library. Subject to "Make variable" substitution and Bourne shell tokenization.

These compiler options are passed to javac after the global compiler options.

Boolean; optional; default is 0

Whether this library should only be used for compilation and not at runtime. Useful if the library will be provided by the runtime environment during execution. Examples of such libraries are the IDE APIs for IDE plug-ins or tools.jar for anything running on a standard JDK.

Note that neverlink = 1 does not prevent the compiler from inlining material from this library into compilation targets that depend on it, as permitted by the Java Language Specification (e.g., static final constants of String or of primitive types). The preferred use case is therefore when the runtime library is identical to the compilation library.

If the runtime library differs from the compilation library then you must ensure that it differs only in places that the JLS forbids compilers to inline (and that must hold for all future versions of the JLS).

plugins

List of labels; optional

Java compiler plugins to run at compile-time. Every java_plugin specified in this attribute will be run whenever this rule is built. A library may also inherit plugins from dependencies that use exported_plugins. Resources generated by the plugin will be included in the resulting jar of this rule.
proguard_specs

List of labels; optional

Files to be used as Proguard specification. These will describe the set of specifications to be used by Proguard. If specified, they will be added to any android_binary target depending on this library. The files included here must only have idempotent rules, namely -dontnote, -dontwarn, assumenosideeffects, and rules that start with -keep. Other options can only appear in android_binary's proguard_specs, to ensure non-tautological merges.
resource_jars

List of labels; optional

Set of archives containing Java resources.

If specified, the contents of these jars are merged into the output jar.

resource_strip_prefix

String; optional

The path prefix to strip from Java resources.

If specified, this path prefix is stripped from every file in the resources attribute. It is an error for a resource file not to be under this directory. If not specified (the default), the path of resource file is determined according to the same logic as the Java package of source files. For example, a source file at stuff/java/foo/bar/a.txt will be located at foo/bar/a.txt.

runtime_deps

List of labels; optional

Libraries to make available to the final binary or test at runtime only. Like ordinary deps, these will appear on the runtime classpath, but unlike them, not on the compile-time classpath. Dependencies needed only at runtime should be listed here. Dependency-analysis tools should ignore targets that appear in both runtime_deps and deps.

java_lite_proto_library

java_lite_proto_library(name, deps, data, compatible_with, deprecation, distribs, features, licenses, restricted_to, tags, testonly, visibility)

java_lite_proto_library generates Java code from .proto files.

deps must point to proto_library rules.

Example:

java_library(
    name = "lib",
    deps = [":foo"],
)

java_lite_proto_library(
    name = "foo",
    deps = [":bar"],
)

proto_library(
    name = "bar",
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of proto_library rules to generate Java code for.

java_proto_library

java_proto_library(name, deps, data, compatible_with, deprecation, distribs, features, licenses, restricted_to, tags, testonly, visibility)

java_proto_library generates Java code from .proto files.

deps must point to proto_library rules.

Example:

java_library(
    name = "lib",
    deps = [":foo_java_proto"],
)

java_proto_library(
    name = "foo_java_proto",
    deps = [":foo_proto"],
)

proto_library(
    name = "foo_proto",
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of proto_library rules to generate Java code for.

java_test

java_test(name, deps, srcs, data, resources, args, classpath_resources, compatible_with, create_executable, deploy_manifest_lines, deprecation, distribs, features, flaky, javacopts, jvm_flags, launcher, licenses, local, main_class, plugins, resource_jars, resource_strip_prefix, restricted_to, runtime_deps, shard_count, size, stamp, tags, test_class, testonly, timeout, use_testrunner, visibility)

A java_test() rule compiles a Java test. A test is a binary wrapper around your test code. The test runner's main method is invoked instead of the main class being compiled.

Implicit output targets

  • name.jar: A Java archive.
  • name_deploy.jar: A Java archive suitable for deployment. (Only built if explicitly requested.) See the description of the name_deploy.jar output from java_binary for more details.

See the section on java_binary() arguments. This rule also supports all attributes common to all test rules (*_test).

Examples

java_library(
    name = "tests",
    srcs = glob(["*.java"]),
    deps = [
        "//java/com/foo/base:testResources",
        "//java/com/foo/testing/util",
    ],
)

java_test(
    name = "AllTests",
    size = "small",
    runtime_deps = [
        ":tests",
        "//util/mysql",
    ],
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of other libraries to be linked in to the target. See general comments about deps at Attributes common to all build rules .
srcs

List of labels; optional

The list of source files that are processed to create the target. This attribute is almost always required; see exceptions below.

Source files of type .java are compiled. In case of generated .java files it is generally advisable to put the generating rule's name here instead of the name of the file itself. This not only improves readability but makes the rule more resilient to future changes: if the generating rule generates different files in the future, you only need to fix one place: the outs of the generating rule. You should not list the generating rule in deps because it is a no-op.

Source files of type .srcjar are unpacked and compiled. (This is useful if you need to generate a set of .java files with a genrule.)

Rules: if the rule (typically genrule or filegroup) generates any of the files listed above, they will be used the same way as described for source files.

This argument is almost always required, except if a main_class attribute specifies a class on the runtime classpath or you specify the runtime_deps argument.

resources

List of labels; optional

A list of data files to include in a Java jar.

If resources are specified, they will be bundled in the jar along with the usual .class files produced by compilation. The location of the resources inside of the jar file is determined by the project structure. Bazel first looks for Maven's standard directory layout, (a "src" directory followed by a "resources" directory grandchild). If that is not found, Bazel then looks for the topmost directory named "java" or "javatests" (so, for example, if a resource is at <workspace root>/x/java/y/java/z, Bazel will use the path y/java/z. This heuristic cannot be overridden.

Resources may be source files or generated files.

classpath_resources

List of labels; optional

DO NOT USE THIS OPTION UNLESS THERE IS NO OTHER WAY)

A list of resources that must be located at the root of the java tree. This attribute's only purpose is to support third-party libraries that require that their resources be found on the classpath as exactly "myconfig.xml". It is only allowed on binaries and not libraries, due to the danger of namespace conflicts.

create_executable

Boolean; optional; nonconfigurable; default is 1

Whether the binary is executable. Non-executable binaries collect transitive runtime Java dependencies into a deploy jar, but cannot be executed directly. No wrapper script is created if this attribute is set. It is an error to set this to 0 if the launcher or main_class attributes are set.
deploy_manifest_lines

List of strings; optional

A list of lines to add to the META-INF/manifest.mf file generated for the *_deploy.jar target. The contents of this attribute are not subject to "Make variable" substitution.
javacopts

List of strings; optional

Extra compiler options for this library. Subject to "Make variable" substitution and Bourne shell tokenization.

These compiler options are passed to javac after the global compiler options.

jvm_flags

List of strings; optional

A list of flags to embed in the wrapper script generated for running this binary. Subject to $(location) and "Make variable" substitution, and Bourne shell tokenization.

The wrapper script for a Java binary includes a CLASSPATH definition (to find all the dependent jars) and invokes the right Java interpreter. The command line generated by the wrapper script includes the name of the main class followed by a "$@" so you can pass along other arguments after the classname. However, arguments intended for parsing by the JVM must be specified before the classname on the command line. The contents of jvm_flags are added to the wrapper script before the classname is listed.

Note that this attribute has no effect on *_deploy.jar outputs.

launcher

Label; optional

Specify a binary that will be used to run your Java program instead of the normal bin/java program included with the JDK. The target must be a cc_binary. Any cc_binary that implements the Java Invocation API can be specified as a value for this attribute.

The special value //tools/jdk:no_launcher indicates that you want to use the normal JDK launcher (bin/java or java.exe) as the value for this attribute. This is the default.

The related --java_launcher Bazel flag affects only those java_binary and java_test targets that have not specified a launcher attribute.

Note that your native (C++, SWIG, JNI) dependencies will be built differently depending on whether you are using the JDK launcher or another launcher:

  • If you are using the normal JDK launcher (the default), native dependencies are built as a shared library named {name}_nativedeps.so, where {name} is the name attribute of this java_binary rule. Unused code is not removed by the linker in this configuration.
  • If you are using any other launcher, native (C++) dependencies are statically linked into a binary named {name}_nativedeps, where {name} is the name attribute of this java_binary rule. In this case, the linker will remove any code it thinks is unused from the resulting binary, which means any C++ code accessed only via JNI may not be linked in unless that cc_library target specifies alwayslink = 1.

When using any launcher other than the default JDK launcher, the format of the *_deploy.jar output changes. See the main java_binary docs for details.

main_class

String; optional

Name of class with main() method to use as entry point. If a rule uses this option, it does not need a srcs=[...] list. Thus, with this attribute one can make an executable from a Java library that already contains one or more main() methods.

The value of this attribute is a class name, not a source file. The class must be available at runtime: it may be compiled by this rule (from srcs) or provided by direct or transitive dependencies (through runtime_deps or deps). If the class is unavailable, the binary will fail at runtime; there is no build-time check.

plugins

List of labels; optional

Java compiler plugins to run at compile-time. Every java_plugin specified in this attribute will be run whenever this rule is built. A library may also inherit plugins from dependencies that use exported_plugins. Resources generated by the plugin will be included in the resulting jar of this rule.
resource_jars

List of labels; optional

Set of archives containing Java resources.

If specified, the contents of these jars are merged into the output jar.

resource_strip_prefix

String; optional

The path prefix to strip from Java resources.

If specified, this path prefix is stripped from every file in the resources attribute. It is an error for a resource file not to be under this directory. If not specified (the default), the path of resource file is determined according to the same logic as the Java package of source files. For example, a source file at stuff/java/foo/bar/a.txt will be located at foo/bar/a.txt.

runtime_deps

List of labels; optional

Libraries to make available to the final binary or test at runtime only. Like ordinary deps, these will appear on the runtime classpath, but unlike them, not on the compile-time classpath. Dependencies needed only at runtime should be listed here. Dependency-analysis tools should ignore targets that appear in both runtime_deps and deps.
stamp

Integer; optional; default is 0

Enable link stamping. Whether to encode build information into the binary. Possible values:
  • stamp = 1: Stamp the build information into the binary. Stamped binaries are only rebuilt when their dependencies change. Use this if there are tests that depend on the build information.
  • stamp = 0: Always replace build information by constant values. This gives good build result caching.
  • stamp = -1: Embedding of build information is controlled by the --[no]stamp flag.
test_class

String; optional

The Java class to be loaded by the test runner.

By default, if this argument is not defined then the legacy mode is used and the test arguments are used instead. Set the --nolegacy_bazel_java_test flag to not fallback on the first argument.

This attribute specifies the name of a Java class to be run by this test. It is rare to need to set this. If this argument is omitted, the Java class whose name corresponds to the name of this java_test rule will be used.

For JUnit3, the test class needs to either be a subclass of junit.framework.TestCase or it needs to have a public static suite() method that returns a junit.framework.Test (or a subclass of Test). For JUnit4, the class needs to be annotated with org.junit.runner.RunWith.

This attribute allows several java_test rules to share the same Test (TestCase, TestSuite, ...). Typically additional information is passed to it (e.g. via jvm_flags=['-Dkey=value']) so that its behavior differs in each case, such as running a different subset of the tests. This attribute also enables the use of Java tests outside the javatests tree.

use_testrunner

Boolean; optional; default is 1

Use the test runner (by default com.google.testing.junit.runner.BazelTestRunner) class as the main entry point for a Java program, and provide the test class to the test runner as a value of bazel.test_suite system property. You can use this to override the default behavior, which is to use test runner for java_test rules, and not use it for java_binary rules. It is unlikely you will want to do this. One use is for AllTest rules that are invoked by another rule (to set up a database before running the tests, for example). The AllTest rule must be declared as a java_binary, but should still use the test runner as its main entry point. The name of a test runner class can be overriden with main_class attribute.

java_plugin

java_plugin(name, deps, srcs, data, resources, compatible_with, deprecation, distribs, features, generates_api, javacopts, licenses, neverlink, output_licenses, plugins, processor_class, proguard_specs, resource_jars, resource_strip_prefix, restricted_to, tags, testonly, visibility)

java_plugin defines plugins for the Java compiler run by Bazel. At the moment, the only supported kind of plugins are annotation processors. A java_library or java_binary rule can run plugins by depending on them via the plugins attribute. A java_library can also automatically export plugins to libraries that directly depend on it using exported_plugins.

Implicit output targets

  • libname.jar: A Java archive.

Arguments are identical to java_library, except for the addition of the processor_class argument.

Arguments

Attributes
name

Name; required

A unique name for this rule.

deps

List of labels; optional

The list of libraries to link into this library. See general comments about deps at Attributes common to all build rules .

The jars built by java_library rules listed in deps will be on the compile-time classpath of this rule. Furthermore the transitive closure of their deps, runtime_deps and exports will be on the runtime classpath.

By contrast, targets in the data attribute are included in the runfiles but on neither the compile-time nor runtime classpath.

srcs

List of labels; optional

The list of source files that are processed to create the target. This attribute is almost always required; see exceptions below.

Source files of type .java are compiled. In case of generated .java files it is generally advisable to put the generating rule's name here instead of the name of the file itself. This not only improves readability but makes the rule more resilient to future changes: if the generating rule generates different files in the future, you only need to fix one place: the outs of the generating rule. You should not list the generating rule in deps because it is a no-op.

Source files of type .srcjar are unpacked and compiled. (This is useful if you need to generate a set of .java files with a genrule.)

Rules: if the rule (typically genrule or filegroup) generates any of the files listed above, they will be used the same way as described for source files.

This argument is almost always required, except if a main_class attribute specifies a class on the runtime classpath or you specify the runtime_deps argument.

data

List of labels; optional

The list of files needed by this library at runtime. See general comments about data at Attributes common to all build rules .

When building a java_library, Bazel doesn't put these files anywhere; if the data files are generated files then Bazel generates them. When building a test that depends on this java_library Bazel copies or links the data files into the runfiles area.

resources

List of labels; optional

A list of data files to include in a Java jar.

If resources are specified, they will be bundled in the jar along with the usual .class files produced by compilation. The location of the resources inside of the jar file is determined by the project structure. Bazel first looks for Maven's standard directory layout, (a "src" directory followed by a "resources" directory grandchild). If that is not found, Bazel then looks for the topmost directory named "java" or "javatests" (so, for example, if a resource is at <workspace root>/x/java/y/java/z, Bazel will use the path y/java/z. This heuristic cannot be overridden.

Resources may be source files or generated files.

generates_api

Boolean; optional; default is 0

This attribute marks annotation processors that generate API code.

If a rule uses an API-generating annotation processor, other rules depending on it can refer to the generated code only if their compilation actions are scheduled after the generating rule. This attribute instructs Bazel to introduce scheduling constraints when --java_header_compilation is enabled.

WARNING: This attribute affects build performance, use it only if necessary.

javacopts

List of strings; optional

Extra compiler options for this library. Subject to "Make variable" substitution and Bourne shell tokenization.

These compiler options are passed to javac after the global compiler options.

Boolean; optional; default is 0

Whether this library should only be used for compilation and not at runtime. Useful if the library will be provided by the runtime environment during execution. Examples of such libraries are the IDE APIs for IDE plug-ins or tools.jar for anything running on a standard JDK.

Note that neverlink = 1 does not prevent the compiler from inlining material from this library into compilation targets that depend on it, as permitted by the Java Language Specification (e.g., static final constants of String or of primitive types). The preferred use case is therefore when the runtime library is identical to the compilation library.

If the runtime library differs from the compilation library then you must ensure that it differs only in places that the JLS forbids compilers to inline (and that must hold for all future versions of the JLS).

output_licenses

null; optional

See common attributes
plugins

List of labels; optional

Java compiler plugins to run at compile-time. Every java_plugin specified in this attribute will be run whenever this rule is built. A library may also inherit plugins from dependencies that use exported_plugins. Resources generated by the plugin will be included in the resulting jar of this rule.
processor_class

String; optional

The processor class is the fully qualified type of the class that the Java compiler should use as entry point to the annotation processor. If not specified, this rule will not contribute an annotation processor to the Java compiler's annotation processing, but its runtime classpath will still be included on the compiler's annotation processor path. (This is primarily intended for use by Error Prone plugins, which are loaded from the annotation processor path using java.util.ServiceLoader.)
proguard_specs

List of labels; optional

Files to be used as Proguard specification. These will describe the set of specifications to be used by Proguard. If specified, they will be added to any android_binary target depending on this library. The files included here must only have idempotent rules, namely -dontnote, -dontwarn, assumenosideeffects, and rules that start with -keep. Other options can only appear in android_binary's proguard_specs, to ensure non-tautological merges.
resource_jars

List of labels; optional

Set of archives containing Java resources.

If specified, the contents of these jars are merged into the output jar.

resource_strip_prefix

String; optional

The path prefix to strip from Java resources.

If specified, this path prefix is stripped from every file in the resources attribute. It is an error for a resource file not to be under this directory. If not specified (the default), the path of resource file is determined according to the same logic as the Java package of source files. For example, a source file at stuff/java/foo/bar/a.txt will be located at foo/bar/a.txt.

java_runtime

java_runtime(name, srcs, compatible_with, deprecation, distribs, features, java_home, licenses, restricted_to, tags, testonly, visibility)

Specifies the configuration for a Java runtime.

Example:

java_runtime(
    name = "jdk-9-ea+153",
    srcs = glob(["jdk9-ea+153/**"]),
    java_home = "jdk9-ea+153",
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

srcs

List of labels; required

All files in the runtime.
java_home

String; optional

The relative path to the root of the runtime.

java_runtime_suite

java_runtime_suite(name, compatible_with, default, deprecation, distribs, features, licenses, restricted_to, runtimes, tags, testonly, visibility)

Specifies the configuration for the Java runtimes for each architecture.

Example:

java_runtime_suite(
   name = "jdk9",
   runtimes = {
     "k8": ":jdk9-k8",
     "ppc": ":jdk9-ppc",
     "arm": ":jdk9-arm",
   },
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

default

Label; optional

The default java_runtime, used if runtimes does not contain an entry for the configured architecture.
runtimes

Dictionary mapping strings to labels; optional

A map from each supported architecture to the corresponding java_runtime.

java_toolchain

java_toolchain(name, bootclasspath, compatible_with, deprecation, distribs, encoding, extclasspath, features, forcibly_disable_header_compilation, genclass, header_compiler, ijar, javabuilder, javac, javac_supports_workers, jvm_opts, licenses, misc, oneversion, oneversion_whitelist, resourcejar, restricted_to, singlejar, source_version, tags, target_version, testonly, timezone_data, visibility, xlint)

Specifies the configuration for the Java compiler. Which toolchain to be used can be changed through the --java_toolchain argument. Normally you should not write those kind of rules unless you want to tune your Java compiler.

Examples

A simple example would be:

java_toolchain(
    name = "toolchain",
    source_version = "7",
    target_version = "7",
    bootclasspath = ["//tools/jdk:bootclasspath"],
    encoding = "UTF-8",
    xlint = [ "classfile", "divzero", "empty", "options", "path" ],
    misc = [ "-g" ],
    javabuilder = ":JavaBuilder_deploy.jar",
)

Arguments

Attributes
name

Name; required

A unique name for this rule.

bootclasspath

List of labels; required

The Java target exdir entries. Corresponds to javac's -bootclasspath flag.
encoding

String; required

The encoding of the java files (e.g., 'UTF-8').
extclasspath

List of labels; required

The Java target exdir entries. Corresponds to javac's -extdir flag.
forcibly_disable_header_compilation

Boolean; optional; default is 0

Overrides --java_header_compilation to disable header compilation on platforms that do not support it, e.g. JDK 7 Bazel.
genclass

List of labels; required

Label of the GenClass deploy jar.
header_compiler

List of labels; optional

Label of the header compiler. Required if --java_header_compilation is enabled.
ijar

List of labels; required

Label of the ijar executable.
javabuilder

List of labels; required

Label of the JavaBuilder deploy jar.
javac

List of labels; required

Label of the javac jar.
javac_supports_workers

Boolean; optional; default is 1

True if JavaBuilder supports running as a persistent worker, false if it doesn't.
jvm_opts

List of strings; optional

The list of arguments for the JVM when invoking the Java compiler. Please refer to the Java virtual machine documentation for the extensive list of possible flags for this option.
misc

List of strings; optional

The list of extra arguments for the Java compiler. Please refer to the Java compiler documentation for the extensive list of possible Java compiler flags.
oneversion

Label; optional

Label of the one-version enforcement binary.
oneversion_whitelist

Label; optional

Label of the one-version whitelist.
resourcejar

List of labels; optional

Label of the resource jar builder executable.
singlejar

List of labels; required

Label of the SingleJar deploy jar.
source_version

String; required

The Java source version (e.g., '6' or '7'). It specifies which set of code structures are allowed in the Java source code.
target_version

String; required

The Java target version (e.g., '6' or '7'). It specifies for which Java runtime the class should be build.
timezone_data

Label; optional

Label of a resource jar containing timezone data. If set, the timezone data is added as an implicitly runtime dependency of all java_binary rules.
xlint

List of strings; optional

The list of warning to add or removes from default list. Precedes it with a dash to removes it. Please see the Javac documentation on the -Xlint options for more information.