Protubuf 定义复杂格式的 message

布满荆棘的人生 2022-09-05 14:55 35阅读 0赞

### 1 摘要 ###

什么是 protobuf? Java Spring boot 如何集成 protobuf? 具体可参考以下博客:

[Spring boot 2.5 集成 Google protocol buffer][Spring boot 2.5 _ Google protocol buffer]

Protobuf 官方文档:

[https://developers.google.com/protocol-buffers][https_developers.google.com_protocol-buffers]

[https://developers.google.com/protocol-buffers/docs/overview][https_developers.google.com_protocol-buffers_docs_overview]

本文将介绍如何定义较为复杂格式的 protobuf 文件，包括对象字段，列表字段，枚举类等

### 2 核心代码 ###

#### 2.1 protobuf 文件 ####

./demo-mybatis-plus/src/main/java/com/ljq/demo/springboot/mybatisplus/model/protobuf/Student.proto

syntax = "proto3";
    
    option optimize_for = CODE_SIZE;
    option java_package = "com.ljq.demo.springboot.mybatisplus.model.entity";
    option java_outer_classname = "StudentPb";
    
    // 学生信息
    message Student {
    
      // id
      int64 id = 1;
      // 姓名
      string name = 2;
      // 出生日期(时间戳)
      int32 birth_date = 3;
    }
    
    // 班级信息
    message ClassInfo {
    
      // id
      int64 id = 1;
      // 年级
      int32 grade = 2;
      // 班级编号
      int32 number = 3;
    
    }
    
    // 学生选修课
    message ElectiveCourse {
    
      // 学生 id
      int64 stu_id = 1;
      // 课程名称
      repeated string course_names = 2;
    
    }
    
    // 学生班级信息
    message StudentClass {
    
      // id
      int64 id = 1;
      // 学生信息
      Student student = 2;
      // 班级信息
      ClassInfo class_info = 3;
    
    }
    
    // 性别
    message StudentSex {
      enum Sex{
        MAN = 0;
        WOMEN = 1;
      }
      Sex sex = 2;
    }
    
    // 教师信息
    message Teacher {
      // id
      uint64 id = 1;
      // 姓名
      string name = 2;
    }

简要说明:

`ElectiveCourse` 选修课 message 中「课程名称」是属于列表形式的

`StudentClass` 学生班级信息中包含 `Student` 和 `ClassInfo` 对象

`StudentSex` 学生性别是枚举类的示例，枚举类元素与其他 message 元素定义的区别在于枚举类的元素下标是从 0 开始的。

**proto 文件定义好之后需要编译，然后才能生成对应的 Java 类**

#### 2.2 测试示例 ####

在生成 Java 类之后进行测试

./demo-mybatis-plus/src/test/java/com/ljq/demo/springboot/mybatisplus/model/entity/StudentPbTest.java

package com.ljq.demo.springboot.mybatisplus.model.entity;
    
    import cn.hutool.core.bean.BeanUtil;
    import cn.hutool.core.bean.copier.CopyOptions;
    import com.ljq.demo.springboot.mybatisplus.model.param.student.StudentReceiveParam;
    import org.junit.Test;
    
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    import java.util.List;
    
    public class StudentPbTest { 
    
    
        /** * 测试-赋值与取值 */
        @Test
        public void value() { 
            // 赋值
            StudentPb.Student student = StudentPb.Student.newBuilder()
                    .setId(111L)
                    .setName("张三")
                    .setBirthDate(1628233076)
                    .build();
            System.out.println(student.toString());
            // 测试结果:
    // id: 111
    // name: "\345\274\240\344\270\211"
    // birth_date: 1628233076
    
            // 测试结论: 字符串的 toString 为编码
    
            // 取值
            System.out.println("id: " + student.getId());
            System.out.println("name: " + student.getName());
            System.out.println("birth_date: " + student.getBirthDate());
            // 测试结果:
    // id: 111
    // name: 张三
    // birth_date: 1628233076
    
            // 测试结论: 逐个属性取值不存在编码问题
    
            // BeanUtil 属性赋值测试
            StudentReceiveParam receiveParam = new StudentReceiveParam();
            BeanUtil.copyProperties(student, receiveParam, CopyOptions.create().ignoreError().ignoreNullValue());
            System.out.println(receiveParam);
            // 测试结果:
    // StudentReceiveParam(id=null, name=null, birth_date=null)
    
            // 测试结论: Protobuf 生成的 java 类无法使用 beanUtil 进行属性复制
        }
    
        /** * 测试-数据转换 */
        @Test
        public void convert() throws IOException { 
            StudentPb.Student student = StudentPb.Student.newBuilder()
                    .setId(111L)
                    .setName("张三")
                    .setBirthDate(1628233076).build();
            // 转化为字节数组
            byte[] bytes = student.toByteArray();
    
            // 写入本地
            String localPath = "/Users/ljq/Downloads/student.bin";
            Files.write(Paths.get(localPath), bytes);
    
            // 从流中读取数据
            byte[] readBytes = Files.readAllBytes(Paths.get(localPath));
            StudentPb.Student readStudent = StudentPb.Student.parseFrom(readBytes);
            // 取值
            System.out.println("id: " + readStudent.getId());
            System.out.println("name: " + readStudent.getName());
            System.out.println("birth_date: " + readStudent.getBirthDate());
        }
    
        /** * 测试-列表字段 */
        @Test
        public void list() { 
            // 赋值
            StudentPb.ElectiveCourse electiveCourse = StudentPb.ElectiveCourse.newBuilder()
                    .setStuId(6L)
                    .addCourseNames("物理")
                    .addCourseNames("化学")
                    .addCourseNames("生物")
                    .build();
            // 取值
            System.out.println("Student id: " + electiveCourse.getStuId());
            List<String> courseNameList = electiveCourse.getCourseNamesList();
            System.out.println("elective course: ");
            courseNameList.stream().forEach(s -> System.out.println(s));
    
        }
    
        /** * 测试-字段为对象 */
        @Test
        public void object() { 
            // 赋值
            StudentPb.StudentClass studentClass = StudentPb.StudentClass.newBuilder()
                    .setId(7L)
                    .setStudent(StudentPb.Student.newBuilder()
                            .setId(123L)
                            .setName("德玛西亚")
                            .setBirthDate(1628233076).build())
                    .setClassInfo(StudentPb.ClassInfo.newBuilder()
                            .setId(456L)
                            .setGrade(3)
                            .setNumber(2).build())
                    .build();
            // 取值
            System.out.println("id: " + studentClass.getId());
            // 学生信息
            System.out.println("student id: " + studentClass.getStudent().getId());
            System.out.println("student name: " + studentClass.getStudent().getName());
            System.out.println("student birth_date: " + studentClass.getStudent().getBirthDate());
            // 班级信息
            System.out.println("class id: " + studentClass.getClassInfo().getId());
            System.out.println("class grade: " + studentClass.getClassInfo().getGrade());
            System.out.println("class number: " + studentClass.getClassInfo().getNumber());
    
        }
    
        /** * 测试-枚举类 */
        @Test
        public void enums() { 
            StudentPb.StudentSex studentSex = StudentPb.StudentSex.newBuilder()
                    .setSex(StudentPb.StudentSex.Sex.MAN)
                    .build();
            // 取值
            System.out.println("student sex: " + studentSex.getSex());
            System.out.println("student sex value: " + studentSex.getSexValue());
            // 测试结果
    // student sex: MAN
    // student sex value: 0
    
            // 测试结论: 直接获取枚举类，返回的是枚举对象/字符串;获取枚举类的值，返回的是枚举类中对应的属性值
            // protobuf 在生成枚举类的时候会默认给每一个枚举值赋值为整数,从 0 开始
    
    
    
        }
    
    }

### 3 推荐参考资料 ###

官方文档 [https://developers.google.com/protocol-buffers][https_developers.google.com_protocol-buffers]

官方文档 [https://developers.google.com/protocol-buffers/docs/overview][https_developers.google.com_protocol-buffers_docs_overview]

官方文档 [Protocol Buffer Basics: Java][Protocol Buffer Basics_ Java]

### 4 Github 源码 ###

**Gtihub 源码地址** : [https://github.com/Flying9001/springBootDemo][https_github.com_Flying9001_springBootDemo]

个人公众号:**404Code**,分享半个互联网人的技术与思考，感兴趣的可以关注.  
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[Spring boot 2.5 _ Google protocol buffer]: https://blog.csdn.net/Mrqiang9001/article/details/119678817
[https_developers.google.com_protocol-buffers]: https://developers.google.com/protocol-buffers
[https_developers.google.com_protocol-buffers_docs_overview]: https://developers.google.com/protocol-buffers/docs/overview
[Protocol Buffer Basics_ Java]: https://developers.google.com/protocol-buffers/docs/javatutorial
[https_github.com_Flying9001_springBootDemo]: https://github.com/Flying9001/springBootDemo
[404Code]: /images/20220829/01d0ce08d5a143df821178d1b69a7c26.png