Thrift示例分析

Thrift文件

namespace java calculator

// 枚举类型
enum Operator{
	ADD,SUB,MUL,DIV
}

// 异常类型(一种特殊的结构体)
exception InvalidationOperator{
	1: i32 what,
	2: string why
}

// 结构体
struct Work{
	1: i32 num1,
	2: i32 num2,
	3: Operator op
}

// 服务
service Calculator{
	
	// 方法定义：类型 方法名(num:变量类型 变量名) throws (num:异常类型 异常变量名)
	i32 calculate(1: Work work) throws (1:InvalidationOperator e)
}

服务端代码

实现Thrift文件中定义的服务接口：

import calculator.Work;
import calculator.Calculator.Iface;
import calculator.InvalidationOperator;

class CalHandler implements Iface{
	
	@Override
	public int calculate(Work work) throws InvalidationOperator, TException {
		switch(work.op){
		case ADD:
			return work.num1 + work.num2;
		case SUB:
			return work.num1 - work.num2;
		case MUL:
			return work.num1*work.num2;
		case DIV:
			if(work.num2 == 0){
				throw new InvalidationOperator(work.op.getValue(), "0不能为除数!");
			}
			return work.num1/work.num2;
		default:
			throw new InvalidationOperator(work.op.getValue(), "未知操作符!");
		}
	}
}

其中 Iface的定义如下所示：

public interface Iface {

    public int calculate(Work work) throws InvalidationOperator, org.apache.thrift.TException;

  }

  public interface AsyncIface {

    public void calculate(Work work, org.apache.thrift.async.AsyncMethodCallback resultHandler) throws org.apache.thrift.TException;

  }

实现服务器监听服务：

public class CalServer {
	public static void main(String[] args) throws TTransportException{
		TServerTransport transport = new TServerSocket(9999);
		CalHandler cal = new CalHandler();
		Processor processor = new Processor(cal);
		TServer server = new TSimpleServer(new Args(transport).processor(processor));
		System.out.println("服务器已开启...");
		server.serve();
	}
}

Thrift的 网络栈如下所示：

  +-------------------------------------------+
  | Server                                    |
  | (single-threaded, event-driven etc)       |
  +-------------------------------------------+
  | Processor                                 |
  | (compiler generated)                      |
  +-------------------------------------------+
  | Protocol                                  |
  | (JSON, compact etc)                       |
  +-------------------------------------------+
  | Transport                                 |
  | (raw TCP, HTTP etc)                       |
  +-------------------------------------------+

• Transport是对底层数据传输的抽象(abstraction for reading/writing from/to the network)，实现了数据传输与数据(反)序列化的解耦。除了典型的socket数据传输方式(TServerSocket)外，Thrift还支持硬盘文件读写(TFileTransport)、缓存读写(TBufferedTransport)、按帧读写(TFramedTransport)、内存读写(TMemoryBuffer)等。
• Protocol定义了内存中的数据格式(in-memory data structures)转换为传输数据格式(wire-format)的方式，换句话说，协议定义了顶层的数据类型与Transport层数据的转换方式(how datatypes use the underlying Transport to encode/decode themselves)。常用的协议包括：JSON，XML，plain text,compact binary等。
• Processor负责从流中读写数据，Processor的构造函数如下所示：
  

  public static class Processor {
    public Processor(I iface) { }

    protected Processor(I iface, Map processMap) {  }

  }

  public static class AsyncProcessor {
    public AsyncProcessor(I iface) {  }

    protected AsyncProcessor(I iface, Map processMap) {   }
	
  }

• Server综合以上所有东西对外提供服务

1. 创建一个Transport
2. 执行基于Transport的数据传输协议
3. 创建基于数据传输协议以及数据传输逻辑的Processor
4. 启动服务，监听客户端请求

客户端代码

public class CalClient {
	public static void main(String[] args) throws InvalidationOperator, TException{
		TTransport transport = new TSocket("localhost", 9999);
		transport.open();
		TProtocol protocol = new TBinaryProtocol(transport);
		Client client = new Client(protocol);
		Work work = new Work(1,2,Operator.ADD);
		int rst = client.calculate(work);
		System.out.println("结果："+rst);
		transport.close();
	}
}