记录:Protocol Buffers(protobuf)在Java开发中使用
1.编写一个.proto文件命名为:addressbook.proto,该文件内容来自protocal-buffers官网
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package tutorial; option java_package = "com.example.tutorial"; option java_outer_classname = "AddressBookProtos"; message Person { required string name = 1;
required int32 id = 2;
optional string email = 3;
enum PhoneType {
MOBILE = 0;
HOME = 1;
WORK = 2;
}
message PhoneNumber {
required string number = 1;
optional PhoneType type = 2 [default = HOME];
}
repeated PhoneNumber phone = 4;
} message AddressBook { repeated Person person = 1;
} |
2.使用protoc-2.6.0-win32.zip解压后的protoc.exe生成Java类
查询protoc.exe帮助:
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D:\__dev\jar\protobuff>protoc.exe -h |
生成Java类:
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D:\__dev\jar\protobuff>protoc.exe --proto_path=F:\__eclipse\test\proto --java_out=F:\__eclipse\test\src F:\__eclipse\test\proto\addressbook.proto |
在Eclipse中的项目目录结构图如下:
说明:
上图中:addressbook.proto数据格式文件,AddressBookProtos.java是生成的java类,protobuf-java-2.5.0.jar是Java运行时类库。
3.使用AddressBookProtos类来实现对象的***和反序列化,了解Protocol-buffers jar的相关API
代码实例:
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package com.example.test;
import java.util.Arrays;
import com.example.tutorial.AddressBookProtos.AddressBook;
import com.example.tutorial.AddressBookProtos.Person;
import com.google.protobuf.InvalidProtocolBufferException;
public class AddressBookProtoUse {
public static void main(String[] args) {
//构建一个Person对象
Person person = Person
.newBuilder()
.setId( 10086 )
.setName( "zhangsan" )
.addPhone(
Person.PhoneNumber.newBuilder().setNumber( "186" )
.setType(Person.PhoneType.HOME).build())
.build();
System.out.println( "打印输出Person对象信息:" );
System.out.println(person);
System.out.println( "Person对象调用toString()方法:" );
System.out.println(person.toString());
System.out.println( "Person对象字段是否初始化:" + person.isInitialized());
// ***
System.out.println( "Person对象调用toByteString()方法:" );
System.out.println(person.toByteString());
System.out.println( "Person对象调用toByteArray()方法:" );
System.out.println(Arrays.toString(person.toByteArray()));
try {
System.out.println( "反序列化后的对象信息:" );
// 反序列化
Person newPerson = Person.parseFrom(person.toByteArray());
System.out.println(newPerson);
newPerson = Person.parseFrom(person.toByteString());
System.out.println(newPerson);
} catch (InvalidProtocolBufferException e) {
e.printStackTrace();
}
// 向地址簿添加两条Person信息
AddressBook.Builder books = AddressBook.newBuilder();
books.addPerson(person);
.build());
System.out.println( "AddressBook对象信息:" );
System.out.println(books.build());
}
} |
运行结果:
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打印输出Person对象信息: name: "zhangsan" id: 10086 email: "[email protected]" phone { number: "186"
type: HOME
} Person对象调用toString()方法: name: "zhangsan" id: 10086 email: "[email protected]" phone { number: "186"
type: HOME
} Person对象字段是否初始化:true Person对象调用toByteString()方法: <[email protected] size=40> Person对象调用toByteArray()方法: [10, 8, 122, 104, 97, 110, 103, 115, 97, 110, 16, -26, 78, 26, 16, 122, 104, 97, 110, 103, 115, 97, 110, 64, 49, 54, 51, 46, 99, 111, 109, 34, 7, 10, 3, 49, 56, 54, 16, 1] 反序列化后的对象信息: name: "zhangsan" id: 10086 email: "[email protected]" phone { number: "186"
type: HOME
} name: "zhangsan" id: 10086 email: "[email protected]" phone { number: "186"
type: HOME
} AddressBook对象信息: person { name: "zhangsan"
id: 10086
email: "[email protected]"
phone {
number: "186"
type: HOME
}
} person { name: "zhangsan"
id: 10086
email: "[email protected]"
phone {
number: "186"
type: HOME
}
} |
探究AddressBookProtos类:
a.构造Person对象,Person类继承自com.google.protobuf.GeneratedMessage类,而GeneratedMessage类继承自AbstractMessage类,并且实现了序列化接口Serializable。在AbstractMessage类中重写了toString()方法,具体内容如下:
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@Override public final String toString() {
return TextFormat.printToString( this );
}
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于是有了Person对象调用toString()方法后直接输出Person对象的文本内容。
b.toByteString()返回的ByteString是一个不可变的byte序列,由AbstractMessage类实现。toByteArray()返回byte[]。这两个方法都是对象进行序列化的方法。
c.isInitialized()判断对象的字段是否初始化,该方法与Person类的initFields()方法相关。
initFields()源代码:
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private void initFields() {
name_ = "" ;
id_ = 0 ;
email_ = "" ;
phone_ = java.util.Collections.emptyList();
}
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initFields()方法的调用是在Person类的默认实力对象初始化之后调用的,在Person类的静态代码块中可以看到:
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static {
defaultInstance = new Person( true );
defaultInstance.initFields();
}
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d.Person类提供了一系列的反序列化的重载方法用来讲数据反序列化为Person对象。
e.关于Person对象的Build
Person类中有一个Builder的内部类,该类用来构建Person对象,并且为Person对象添加数据。
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public static final class Builder extends
com.google.protobuf.GeneratedMessage.Builder<Builder>
implements com.example.tutorial.AddressBookProtos.PersonOrBuilder
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4.通过学习官网的实例,手绘一张Java使用protobuf的基本流程图
本文转自 secondriver 51CTO博客,原文链接:http://blog.51cto.com/aiilive/1563449,如需转载请自行联系原作者