android_accessing_cpp_switches_in_java.md 3.2 KB

Accessing C++ Switches In Java

[TOC]

Introduction

Accessing C++ switches in Java is implemented via a Python script which analyzes the C++ switches file and generates the corresponding Java class, based on a template file. The template file must be specified in the GN target.

Usage

  1. Create a template file (ex. FooSwitches.java.tmpl). Change «Copyright 2020» to be whatever the year is at the time of writing (as you would for any other file). ```java // Copyright 2020 The Chromium Authors. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file.

    package org.chromium.foo;

    // Be sure to escape any curly braces in your template by doubling as // follows. /**

    • Contains command line switches that are specific to the foo project. */ public final class FooSwitches {{

    {NATIVE_STRINGS}

    // Prevents instantiation.
    private FooSwitches() {{}}
    

    }}

    
    2. Add a new build target and add it to the `srcjar_deps` of an
    `android_library` target:
    
    ```gn
    if (is_android) {
      import("//build/config/android/rules.gni")
    }
    
    if (is_android) {
      java_cpp_strings("java_switches_srcjar") {
        # External code should depend on ":foo_java" instead.
        visibility = [ ":*" ]
        sources = [
          "//base/android/foo_switches.cc",
        ]
        template = "//base/android/java_templates/FooSwitches.java.tmpl"
      }
    
      # If there's already an android_library target, you can add
      # java_switches_srcjar to that target's srcjar_deps. Otherwise, the best
      # practice is to create a new android_library just for this target.
      android_library("foo_java") {
        srcjar_deps = [ ":java_switches_srcjar" ]
      }
    }
    
  2. The generated file out/Default/gen/.../org/chromium/foo/FooSwitches.java would contain:

    ```java // Copyright $YEAR The Chromium Authors. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file.

    package org.chromium.foo;

    /**

    • Contains command line switches that are specific to the foo project. */ public final class FooSwitches {

      // …snip…

      // This following string constants were inserted by // java_cpp_strings.py // From // ../../base/android/foo_switches.cc // Into // ../../base/android/java_templates/FooSwitches.java.tmpl

      // Documentation for the C++ switch is copied here. public static final String SOME_SWITCH = «some-switch»;

      // …snip…

      // Prevents instantiation. private FooSwitches() {} } ```

      See also

      Code