android_accessing_cpp_switches_in_java.md

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 spits out the corresponding Java class. The generated class name will be based upon the switch file name, and the path must be specified in a comment within the switch file itself.

Usage

1. Create a template file (ex. FooSwitches.java.tmpl)

    // Copyright $YEAR The Chromium Authors. All rights reserved.
    // 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

   import("//build/config/android/rules.gni")
   
   java_cpp_strings("java_switches") {
     sources = [
       "//base/android/foo_switches.cc",
     ]
     template = "//base/android/java_templates/FooSwitches.java.tmpl"
   }

3. Add the new target to the desired android_library targets srcjar_deps:

   android_library("base_java") {
     srcjar_deps = [
       ":java_switches",
     ]
   }

4. The generated file out/Default/gen/.../org/chromium/foo/FooSwitches.java would contain:

   // Copyright $YEAR The Chromium Authors. All rights reserved.
   // 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() {}
   }

Code

• Generator code and Tests
• GN template