Wire：整洁的轻量级协议缓存

Java , Wire , 数据结构

Wire是一个简洁的轻量级协议缓存，针对Android与Java平台。Wire与Square无关，是完全独立的缓存实现，特别针对Android与Java平台设计。

功能特性

对schema中定义的每种消息类型，Wire都会生成一个不可变（immutable）模型类及builder。生成的代码质量与手写一致，代码包含文档说明、已排版并且非常简洁。如果你喜欢Effective Java，相信Wire的API会让你感到非常亲切。

也就是说，Wire的设计包含了以下特点：

Wire消息声明：放弃通常的getter方法，使用public final字段，简化了代码生成与代码执行。减少代码量在Android应用中的好处尤其明显。
Wire避免了大小写映射：在schema中定义的picture_urls字段，会对应生成名为picture_urls的Java字段，而非传统的pictureUrls驼峰式命名。尽管名称开始看起来有些怪，对于grep或者其他复杂的搜索工具来说却很方便。这种做法不再需要schema、Java源代码、数据之间的映射。不仅如此，在调用特殊的消息时还能起到友好的提示。
基础类型装箱：如果缺少某个字段，它的值null，适用于非必须的字段。例如恐龙锁处的时间代未知。在schema升级的过程中字段也可能变为null：如果明天再消息中增加一个carnivore的boolean字段，那么今天的数据中则会缺少这个字段。

下载

wire-runtime包含了使用Wire生成代码的应用程序运行时必须包含的支持库：

Maven

<dependency>
  <groupId>com.squareup.wire</groupId>
  <artifactId>wire-runtime</artifactId>
  <version>2.2.0</version>
</dependency>

<groupId>com.squareup.wire</groupId>

<artifactId>wire-runtime</artifactId>

</dependency>

Gradle

compile 'com.squareup.wire:wire-runtime:2.2.0'

1	compile 'com.squareup.wire:wire-runtime:2.2.0'

开发版本的镜像可以从Sonatype snapshots仓库下载。

使用示例

定义Dinosaur消息

下面是一个消息定义示例：

Java
syntax = "proto2";

package squareup.dinosaurs;

option java_package = "com.squareup.dinosaurs";

import "squareup/geology/period.proto";

message Dinosaur {
  // Common name of this dinosaur, like "Stegosaurus".
  optional string name = 1;

  // URLs with images of this dinosaur.
  repeated string picture_urls = 2;

  optional squareup.geology.Period period = 5;
}

				
					
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						syntax = "proto2";
 
package squareup.dinosaurs;
 
option java_package = "com.squareup.dinosaurs";
 
import "squareup/geology/period.proto";
 
message Dinosaur {
  // Common name of this dinosaur, like "Stegosaurus".
  optional string name = 1;
 
  // URLs with images of this dinosaur.
  repeated string picture_urls = 2;
 
  optional squareup.geology.Period period = 5;
}

					

			

这是一个enum定义：

syntax = "proto2";

package squareup.geology;

option java_package = "com.squareup.geology";

enum Period {
  // 145.5 million years ago — 66.0 million years ago.
  CRETACEOUS = 1;

  // 201.3 million years ago — 145.0 million years ago.
  JURASSIC = 2;

  // 252.17 million years ago — 201.3 million years ago.
  TRIASSIC = 3;
}

				
					
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						syntax = "proto2";
 
package squareup.geology;
 
option java_package = "com.squareup.geology";
 
enum Period {
  // 145.5 million years ago — 66.0 million years ago.
  CRETACEOUS = 1;
 
  // 201.3 million years ago — 145.0 million years ago.
  JURASSIC = 2;
 
  // 252.17 million years ago — 201.3 million years ago.
  TRIASSIC = 3;
}

					

			

生成的Java代码

下面是Dinosaur消息生成的一个紧凑的定义：

// Code generated by Wire protocol buffer compiler, do not edit.
// Source file: squareup/dinosaurs/dinosaur.proto at 9:1
package com.squareup.dinosaurs;

import com.squareup.geology.Period;
import com.squareup.wire.Message;
import com.squareup.wire.ProtoAdapter;
import com.squareup.wire.WireField;
import java.util.List;
import okio.ByteString;

public final class Dinosaur extends Message<Dinosaur, Dinosaur.Builder> {
  public static final ProtoAdapter<Dinosaur> ADAPTER = ProtoAdapter.newMessageAdapter(Dinosaur.class);

  private static final long serialVersionUID = 0L;

  public static final String DEFAULT_NAME = "";

  public static final Period DEFAULT_PERIOD = Period.CRETACEOUS;

  /**
   * Common name of this dinosaur, like "Stegosaurus".
   */
  @WireField(
      tag = 1,
      adapter = "com.squareup.wire.ProtoAdapter#STRING"
  )
  public final String name;

  /**
   * URLs with images of this dinosaur.
   */
  @WireField(
      tag = 2,
      adapter = "com.squareup.wire.ProtoAdapter#STRING",
      label = WireField.Label.REPEATED
  )
  public final List<String> picture_urls;

  @WireField(
      tag = 5,
      adapter = "com.squareup.geology.Period#ADAPTER"
  )
  public final Period period;

  public Dinosaur(String name, List<String> picture_urls, Period period) {
    this(name, picture_urls, period, ByteString.EMPTY);
  }

  public Dinosaur(String name, List<String> picture_urls, Period period, ByteString unknownFields) {
    super(unknownFields);
    this.name = name;
    this.picture_urls = immutableCopyOf("picture_urls", picture_urls);
    this.period = period;
  }

  @Override
  public Builder newBuilder() {
    Builder builder = new Builder();
    builder.name = name;
    builder.picture_urls = copyOf("picture_urls", picture_urls);
    builder.period = period;
    builder.addUnknownFields(unknownFields());
    return builder;
  }

  @Override
  public boolean equals(Object other) {
    if (other == this) return true;
    if (!(other instanceof Dinosaur)) return false;
    Dinosaur o = (Dinosaur) other;
    return equals(unknownFields(), o.unknownFields())
        && equals(name, o.name)
        && equals(picture_urls, o.picture_urls)
        && equals(period, o.period);
  }

  @Override
  public int hashCode() {
    int result = super.hashCode;
    if (result == 0) {
      result = unknownFields().hashCode();
      result = result * 37 + (name != null ? name.hashCode() : 0);
      result = result * 37 + (picture_urls != null ? picture_urls.hashCode() : 1);
      result = result * 37 + (period != null ? period.hashCode() : 0);
      super.hashCode = result;
    }
    return result;
  }

  public static final class Builder extends com.squareup.wire.Message.Builder<Dinosaur, Builder> {
    public String name;

    public List<String> picture_urls;

    public Period period;

    public Builder() {
      picture_urls = newMutableList();
    }

    /**
     * Common name of this dinosaur, like "Stegosaurus".
     */
    public Builder name(String name) {
      this.name = name;
      return this;
    }

    /**
     * URLs with images of this dinosaur.
     */
    public Builder picture_urls(List<String> picture_urls) {
      checkElementsNotNull(picture_urls);
      this.picture_urls = picture_urls;
      return this;
    }

    public Builder period(Period period) {
      this.period = period;
      return this;
    }

    @Override
    public Dinosaur build() {
      return new Dinosaur(name, picture_urls, period, buildUnknownFields());
    }
  }
}

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// Code generated by Wire protocol buffer compiler, do not edit.

// Source file: squareup/dinosaurs/dinosaur.proto at 9:1

package com.squareup.dinosaurs;

import com.squareup.geology.Period;

import com.squareup.wire.Message;

import com.squareup.wire.ProtoAdapter;

import com.squareup.wire.WireField;

import java.util.List;

import okio.ByteString;

public final class Dinosaur extends Message<Dinosaur, Dinosaur.Builder> {

public static final ProtoAdapter<Dinosaur> ADAPTER = ProtoAdapter.newMessageAdapter(Dinosaur.class);

private static final long serialVersionUID = 0L;

public static final String DEFAULT_NAME = "";

public static final Period DEFAULT_PERIOD = Period.CRETACEOUS;

/**

* Common name of this dinosaur, like "Stegosaurus".

@WireField(

tag = 1,

adapter = "com.squareup.wire.ProtoAdapter#STRING"

)

public final String name;

/**

* URLs with images of this dinosaur.

@WireField(

tag = 2,

adapter = "com.squareup.wire.ProtoAdapter#STRING",

label = WireField.Label.REPEATED

)

public final List<String> picture_urls;

@WireField(

tag = 5,

adapter = "com.squareup.geology.Period#ADAPTER"

)

public final Period period;

public Dinosaur(String name, List<String> picture_urls, Period period) {

this(name, picture_urls, period, ByteString.EMPTY);

}

public Dinosaur(String name, List<String> picture_urls, Period period, ByteString unknownFields) {

super(unknownFields);

this.name = name;

this.picture_urls = immutableCopyOf("picture_urls", picture_urls);

this.period = period;

}

@Override

public Builder newBuilder() {

Builder builder = new Builder();

builder.name = name;

builder.picture_urls = copyOf("picture_urls", picture_urls);

builder.period = period;

builder.addUnknownFields(unknownFields());

return builder;

}

@Override

public boolean equals(Object other) {

if (other == this) return true;

if (!(other instanceof Dinosaur)) return false;

Dinosaur o = (Dinosaur) other;

return equals(unknownFields(), o.unknownFields())

&& equals(name, o.name)

&& equals(picture_urls, o.picture_urls)

&& equals(period, o.period);

}

@Override

public int hashCode() {

int result = super.hashCode;

if (result == 0) {

result = unknownFields().hashCode();

result = result * 37 + (name != null ? name.hashCode() : 0);

result = result * 37 + (picture_urls != null ? picture_urls.hashCode() : 1);

result = result * 37 + (period != null ? period.hashCode() : 0);

super.hashCode = result;

}

return result;

}

public static final class Builder extends com.squareup.wire.Message.Builder<Dinosaur, Builder> {

public String name;

public List<String> picture_urls;

public Period period;

public Builder() {

picture_urls = newMutableList();

}

/**

* Common name of this dinosaur, like "Stegosaurus".

public Builder name(String name) {

this.name = name;

return this;

}

/**

* URLs with images of this dinosaur.

public Builder picture_urls(List<String> picture_urls) {

checkElementsNotNull(picture_urls);

this.picture_urls = picture_urls;

return this;

}

public Builder period(Period period) {

this.period = period;

return this;

}

@Override

public Dinosaur build() {

return new Dinosaur(name, picture_urls, period, buildUnknownFields());

}

创建proto模型访问的Java代码非常简洁，可读性很好：

Java
Dinosaur stegosaurus = new Dinosaur.Builder()
    .name("Stegosaurus")
    .period(Period.JURASSIC)
    .build();

System.out.println("My favorite dinosaur existed in the " + stegosaurus.period + " period.");

				
					
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						Dinosaur stegosaurus = new Dinosaur.Builder()
    .name("Stegosaurus")
    .period(Period.JURASSIC)
    .build();
 
System.out.println("My favorite dinosaur existed in the " + stegosaurus.period + " period.");

					

			

每个类型都有一个对应的ProtoAdapter，可以把消息编码为字节并把字节解码为消息。

Java
Dinosaur stegosaurus = ...
byte[] stegosaurusBytes = Dinosaur.ADAPTER.encode(stegosaurus);

byte[] tyrannosaurusBytes = ...
Dinosaur tyrannosaurus = Dinosaur.ADAPTER.decode(tyrannosaurusBytes);

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						Dinosaur stegosaurus = ...
byte[] stegosaurusBytes = Dinosaur.ADAPTER.encode(stegosaurus);
 
byte[] tyrannosaurusBytes = ...
Dinosaur tyrannosaurus = Dinosaur.ADAPTER.decode(tyrannosaurusBytes);

访问字段时，使用Wire.get()用默认值替换null：

Java
Period period = Wire.get(stegosaurus.period, Dinosaur.DEFAULT_PERIOD);

				1

						Period period = Wire.get(stegosaurus.period, Dinosaur.DEFAULT_PERIOD);

上面的操作与下面等价：

Period period = stegosaurus.period != null ? stegosaurus.period : Dinosaur.DEFAULT_PERIOD;

1	Period period = stegosaurus.period != null ? stegosaurus.period : Dinosaur.DEFAULT_PERIOD;

生成代码工具

Wire编译器可以通过Maven插件安装。把 .proto 源代码放到项目中 src/main/proto 的目录，通过插件生成 .java 文件。插件会自动把生成的Java代码添加到项目源代码根目录。

XHTML
<build>
  <plugins>
    <plugin>
      <groupId>com.squareup.wire</groupId>
      <artifactId>wire-maven-plugin</artifactId>
      <version>${project.version}</version>
      <executions>
        <execution>
          <phase>generate-sources</phase>
          <goals>
            <goal>generate-sources</goal>
          </goals>
          <configuration>
            <includes>
              <!-- proto package names to generate code for -->
              <include>squareup.dinosaurs.*</include>
              <include>squareup.geology.*</include>
            </includes>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

				
					
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						<build>
  <plugins>
    <plugin>
      <groupId>com.squareup.wire</groupId>
      <artifactId>wire-maven-plugin</artifactId>
      <version>${project.version}</version>
      <executions>
        <execution>
          <phase>generate-sources</phase>
          <goals>
            <goal>generate-sources</goal>
          </goals>
          <configuration>
            <includes>
              <!-- proto package names to generate code for -->
              <include>squareup.dinosaurs.*</include>
              <include>squareup.geology.*</include>
            </includes>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

					

			

Wire从本地文件与.jar文件中读取.proto文件。

编译器会将schema删减为一组根类型（root type）子集，并处理相关的类型。这在项目之前分享schema信息非常有用：Java服务与Android app可以使用共享schema的一组子集。

如果不用Maven，编译器还提供了一组命令行接口。只要将wire-compiler-VERSION-jar-with-dependencies.jar替换为jar路径即可。

% java -jar wire-compiler-VERSION-jar-with-dependencies.jar \
    --proto_path=src/main/proto \
    --java_out=out \
    squareup/dinosaurs/dinosaur.proto \
    squareup/geology/period.proto
Writing com.squareup.dinosaurs.Dinosaur to out
Writing com.squareup.geology.Period to out

% java -jar wire-compiler-VERSION-jar-with-dependencies.jar \

--proto_path=src/main/proto \

--java_out=out \

squareup/dinosaurs/dinosaur.proto \

squareup/geology/period.proto

Writing com.squareup.dinosaurs.Dinosaur to out

Writing com.squareup.geology.Period to out

如果使用Proguard，需要添加keep规则。最简单的方式是让Proguard不要访问Wire运行时库与生成的协议缓存（当然这些代码也就不会被优化处理）：

-keep class com.squareup.wire.** { *; }
-keep class com.yourcompany.yourgeneratedcode.** { *; }

1 2	-keep class com.squareup.wire.** { ; } -keep class com.yourcompany.yourgeneratedcode.* { *; }

使用许可

Wire遵循Apache 2.0开源协议发布。

开源地址：https://github.com/square/wire

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