spring mvc 4.1支持protobuf converters

最近公司有个项目需要和c++做信息交换，现在流行比较流行http+protobuf方式，一是比较简单学习成本低，二是信息的压缩比例比较好，节省带宽。

经过调研spring 4.1以后开始支持protobuf HttpMessageConverter 详细的配置如下：

• pom.xml配置：

<dependency>
    <groupId>com.google.protobuf</groupId>
    <artifactId>protobuf-java</artifactId>
    <version>2.5.0</version>
</dependency>

<dependency>
    <groupId>com.googlecode.protobuf-java-format</groupId>
    <artifactId>protobuf-java-format</artifactId>
    <version>1.2</version>
</dependency>
还有要引入spring核心包及spring mvc包 版本4.1.6.RELEASE，如果不知道怎么引入，百度一下

配置portoc插件，也可以不用这个插件，得需要自己用protoc.exe生产java文件

<plugin>
    <groupId>com.google.protobuf.tools</groupId>
    <artifactId>maven-protoc-plugin</artifactId>
    <version>0.1.10</version>
    <executions>
        <execution>
            <id>generate-sources</id>
            <goals>
                <goal>compile</goal>
            </goals>
            <phase>generate-sources</phase>
            <configuration>
                <protoSourceRoot>${basedir}/src/main/proto/</protoSourceRoot>
                <includes>
                    <param>**/*.proto</param>
                </includes>
            </configuration>
        </execution>
    </executions>
    <configuration>
        <protocExecutable>D:/dev/protoc.exe</protocExecutable><!--protoc.exe文件地址,使用2.5版本-->
    </configuration>
</plugin>

• springmvc-servlet.xml配置

<mvc:annotation-driven>
    <mvc:message-converters>
　　　　<!--看了一下源码，客户端请求类型必须设置成application/x-protobuf采用用这个类来解析实体

        <bean class="org.springframework.http.converter.protobuf.ProtobufHttpMessageConverter">

        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

• user.proto文件，目录/src/main/proto/和protoc插件配置路径保持一致，如果不想用插件可以自己用protoc.exe生成java文件，可以参见protobuf使用

package com.my.pb;

 option java_package = "com.my.pb";

 option java_outer_classname = "UserProto";

 message User {
   optional int64 id = 1;
   optional string name = 2;
   message PhoneNumber {
       required string number = 1;
     }
     repeated PhoneNumber phone = 4;
 }

• controller类

@Controller
public class ProtobufController{
        
    @RequestMapping(value = "/proto/write1",method= RequestMethod.POST)
    public ResponseEntity<UserProto.User> protoWrite1(RequestEntity<UserProto.User> requestEntity) {
        //System.out.println("server===
");
        UserProto.User user =  requestEntity.getBody();
        System.out.println("server===
" + user);
        return ResponseEntity.ok(user);
    }
}

• 客户端测试代码，使用Apache的httpclient进行测试

@Test
    public void testWrite() throws IOException {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(baseUri+"/proto/write1");

        UserProto.User user =   UserProto.User.newBuilder().setId(1).setName("zhangsan").addPhone(UserProto.User.PhoneNumber.newBuilder().setNumber("18611163408")).build();//构造

        ByteArrayInputStream inputStream = new ByteArrayInputStream(user.toByteArray());
        InputStreamEntity inputStreamEntity = new InputStreamEntity(inputStream);

　　　　//这两行很重要的，是告诉springmvc客户端请求和响应的类型，指定application/x-protobuf类型,spring会用ProtobufHttpMessageConverter类来解析请求和响应的实体

        httpPost.addHeader("Content-Type","application/x-protobuf");
        httpPost.addHeader("Accept", "application/x-protobuf");
        
　　　　　httpPost.setEntity(inputStreamEntity);
        CloseableHttpResponse response2 = httpclient.execute(httpPost);

        try {
            System.out.println(response2.getStatusLine());
            HttpEntity entity2 = response2.getEntity();

            ByteArrayOutputStream buf = new ByteArrayOutputStream();
            entity2.writeTo(buf);
            System.out.println(new String(buf.toByteArray())+"#################");
            UserProto.User user2 = UserProto.User.parseFrom(buf.toByteArray());
            System.out.println(user2);
        } finally {
            response2.close();
        }
    }

• 总结：

当时调试的时候试了很多次，响应总是被转成xml类型，最后看了源码才发现客户端要设置httpPost.addHeader("Accept", "application/x-protobuf");
其实也可以自己实现HttpMessageConverter，也不是很麻烦，本人比较懒，有现成的东西不太爱闭门造车轮。

参考文献：
http://jinnianshilongnian.iteye.com/blog/2107205
http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/