Thrift示例分析

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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{@Overridepublic 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<CalHandler> processor = new Processor<CalHandler>(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<I extends Iface> {    public Processor(I iface) { }    protected Processor(I iface, Map<String, ProcessFunction> processMap) {  }  }  public static class AsyncProcessor<I extends AsyncIface> {    public AsyncProcessor(I iface) {  }    protected AsyncProcessor(I iface, Map<String, AsyncProcessFunction> processMap) {   }<span style="white-space:pre"></span>  }

Server综合以上所有东西对外提供服务

创建一个Transport
执行基于Transport的数据传输协议
创建基于数据传输协议以及数据传输逻辑的Processor
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();}}

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