Question

我试图了解Apache的HttpComponents是如何工作的，但是复杂性和类的层次很多。

我正在使用Apache提供的示例代码之一（在线提供的其他代码很少），Basic HTTP GET

即使我查看源代码，我也特别不明白这三行中发生了什么。

httpexecutor.preProcess(request, httpproc, coreContext);
HttpResponse response = httpexecutor.execute(request, conn, coreContext);
httpexecutor.postProcess(response, httpproc, coreContext);

有明确理解的人可以解释一下吗？

以下是完整的代码：

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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package org.apache.http.examples;

import java.net.Socket;

import org.apache.http.ConnectionReuseStrategy;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.impl.DefaultBHttpClientConnection;
import org.apache.http.impl.DefaultConnectionReuseStrategy;
import org.apache.http.message.BasicHttpRequest;
import org.apache.http.protocol.HttpCoreContext;
import org.apache.http.protocol.HttpProcessor;
import org.apache.http.protocol.HttpProcessorBuilder;
import org.apache.http.protocol.HttpRequestExecutor;
import org.apache.http.protocol.RequestConnControl;
import org.apache.http.protocol.RequestContent;
import org.apache.http.protocol.RequestExpectContinue;
import org.apache.http.protocol.RequestTargetHost;
import org.apache.http.protocol.RequestUserAgent;
import org.apache.http.util.EntityUtils;

/**
 * Elemental example for executing multiple GET requests sequentially.
 */
public class ElementalHttpGet {

    public static void main(String[] args) throws Exception {
        HttpProcessor httpproc = HttpProcessorBuilder.create()
            .add(new RequestContent())
            .add(new RequestTargetHost())
            .add(new RequestConnControl())
            .add(new RequestUserAgent("Test/1.1"))
            .add(new RequestExpectContinue(true)).build();

        HttpRequestExecutor httpexecutor = new HttpRequestExecutor();

        HttpCoreContext coreContext = HttpCoreContext.create();
        HttpHost host = new HttpHost("localhost", 8080);
        coreContext.setTargetHost(host);

        DefaultBHttpClientConnection conn = new DefaultBHttpClientConnection(8 * 1024);
        ConnectionReuseStrategy connStrategy = DefaultConnectionReuseStrategy.INSTANCE;

        try {

            String[] targets = {
                    "/",
                    "/servlets-examples/servlet/RequestInfoExample",
                    "/somewhere%20in%20pampa"};

            for (int i = 0; i < targets.length; i++) {
                if (!conn.isOpen()) {
                    Socket socket = new Socket(host.getHostName(), host.getPort());
                    conn.bind(socket);
                }
                BasicHttpRequest request = new BasicHttpRequest("GET", targets[i]);
                System.out.println(">> Request URI: " + request.getRequestLine().getUri());

                httpexecutor.preProcess(request, httpproc, coreContext);
                HttpResponse response = httpexecutor.execute(request, conn, coreContext);
                httpexecutor.postProcess(response, httpproc, coreContext);

                System.out.println("<< Response: " + response.getStatusLine());
                System.out.println(EntityUtils.toString(response.getEntity()));
                System.out.println("==============");
                if (!connStrategy.keepAlive(response, coreContext)) {
                    conn.close();
                } else {
                    System.out.println("Connection kept alive...");
                }
            }
        } finally {
            conn.close();
        }
    }

}

Answer 1

这是一个相当常见的责任链模式，其中每个协议拦截器为所有传出和传入消息强制执行HTTP协议的一个特定方面。

无法理解HttpComponents的复杂性：预处理，后处理，执行器等

1 个答案: