Android12中JAVA项目中proto文件的编译方式

一. 起因

最近的工作有涉及到将原来Android9平台下的java工程防到Android12中编译，结果发现在Android9中可以编译的工程，没有修改Android.bp，在Android12中编译失败了，原因是java文件中以来项目中的proto文件生成的java类，而这些proto文件没有编译出来。

然后找了Android仓库中原生仓库中也有这种需求的代码，例如protobuf，发现其Android.bp中对于proto文件的编译方式发生变化了。

二. 差异

2.1 Android9中的编译方式：

// Java full library (for host-side users)
// =======================================================
java_library_host {
    name: "libprotobuf-java-full",
    defaults: ["libprotobuf_errorprone_defaults"],
 
    srcs: [
        "java/core/src/main/java/**/*.java",
        ":libprotobuf-internal-protos",
    ],

    proto: {
        type: "full",
        local_include_dirs: [
            "src",
        ],
        canonical_path_from_root: false,
    },

    java_version: "1.7",
}

2.2 Android12中的编译方式：

filegroup {
    name: "libprotobuf-internal-protos",
    srcs: [
        "src/google/protobuf/descriptor.proto",
        "src/google/protobuf/any.proto",
        "src/google/protobuf/source_context.proto",
        "src/google/protobuf/type.proto",
        "src/google/protobuf/compiler/plugin.proto",
        "src/google/protobuf/api.proto",
        "src/google/protobuf/duration.proto",
        "src/google/protobuf/empty.proto",
        "src/google/protobuf/field_mask.proto",
        "src/google/protobuf/struct.proto",
        "src/google/protobuf/timestamp.proto",
        "src/google/protobuf/wrappers.proto",
    ],
    path: "src",
}

// Java full library (for host-side users)
// =======================================================
java_library_host {
    name: "libprotobuf-java-full",
    defaults: ["libprotobuf_errorprone_defaults"],

    srcs: [
        "java/core/src/main/java/**/*.java",
        ":libprotobuf-internal-protos",
    ],

    proto: {
        type: "full",
        local_include_dirs: [
            "src",
        ],
        canonical_path_from_root: false,
    },

    java_version: "1.7",
}