本文共 5708 字，大约阅读时间需要 19 分钟。

一，简介

经常看见大家用HttpClient发送http请求，其实Java也自带了相关类库，本篇简单做个介绍，主要是给个示例。

二，环境搭建

首先搭建一个Java Web项目JavaNetDemo，并写一个Servlet用于接受Http请求并返回结果用于测试，代码如下：

package http;import java.io.IOException;import java.io.PrintWriter;import java.io.UnsupportedEncodingException;import java.net.URLDecoder;import java.net.URLEncoder;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 用来测试是否调用到了LoginServlet * @author 猫哥 * @date 2017.4.27 */@WebServlet(urlPatterns="/LoginServlet")public class LoginServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setCharacterEncoding("UTF-8");        request.setCharacterEncoding("UTF-8");        response.setContentType("text/html");        PrintWriter out = response.getWriter();        out.println("");        out.println("");        out.println("  ");        out.println("  ");        out.println("doGet方法调用了");        String name=request.getParameter("name");        out.println("name:"+this.parseGet(name));        String password=request.getParameter("password");        out.println("password:"+this.parseGet(password));        out.println("  ");        out.println("");        out.flush();        out.close();    }    /**     *      * @param input     * @return     * @throws UnsupportedEncodingException     */    private String parseGet(String input) throws UnsupportedEncodingException{        input = URLEncoder.encode(input, "iso8859-1");          input=URLDecoder.decode(input, "utf-8");         return input;    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setCharacterEncoding("UTF-8");        request.setCharacterEncoding("UTF-8");        response.setContentType("text/html");        PrintWriter out = response.getWriter();        out.println("");        out.println("");        out.println("  ");        out.println("  ");        out.println("doPost方法调用了");        String name=request.getParameter("name");        out.println("name:"+name);        String password=request.getParameter("password");        out.println("name:"+password);        out.println("  ");        out.println("");        out.flush();        out.close();    }}

三，Http请求类

注意该类的两个静态方法分别给出了通过代码发送http GET和POST请求的具体例子，发送请求时的参数封装为QueryParams类用于保存参数。

package http;import java.io.BufferedInputStream;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStreamWriter;import java.io.UnsupportedEncodingException;import java.net.URL;import java.net.URLConnection;/** * Http请求发起类 * @author 猫哥 * @date 2017.4.27 */public class HttpSender {    /**     * 测试入口     * @throws UnsupportedEncodingException      */    public static void main(String[] args) throws UnsupportedEncodingException{        String getResult=HttpSender.sendPostRequest();        System.out.println(getResult);    }    /**     * 发起http GET请求     * @return 请求的返回值     */    public static String sendGetRequest(){        StringBuilder sb=new StringBuilder();        QueryParams suffix=new QueryParams();        suffix.add("name", "猫哥");        suffix.add("password","1234");        try {            URL url=new URL("http://127.0.0.1:8080/JavaNetDemo/LoginServlet?x=0"+suffix.toString());            InputStream in=new BufferedInputStream(url.openStream());            BufferedReader reader = new BufferedReader(new InputStreamReader(in,"UTF-8"));            String line;            while((line=reader.readLine())!=null){                sb.append(line);            }        } catch (Exception e) {            e.printStackTrace();        }        return sb.toString();    }    public static String sendPostRequest(){        StringBuilder sb=new StringBuilder();        QueryParams suffix=new QueryParams();        suffix.add("name", "猫哥");        suffix.add("password","1234");        try {            //打开post通道            URL url=new URL("http://127.0.0.1:8080/JavaNetDemo/LoginServlet");            URLConnection urlCon=url.openConnection();            urlCon.setDoOutput(true);               //写参数            OutputStreamWriter out=new OutputStreamWriter(urlCon.getOutputStream(),"UTF-8");            out.write(suffix.toString());            out.flush();            out.close();            //读返回            BufferedReader reader = new BufferedReader(new InputStreamReader(urlCon.getInputStream(),"UTF-8"));            String line;            while((line=reader.readLine())!=null){                sb.append(line);            }        } catch (Exception e) {            e.printStackTrace();            System.out.println(e.getMessage());        }        return sb.toString();    }}

四，QueryParams参数类

package http;import java.io.UnsupportedEncodingException;import java.net.URLEncoder;/** * 参数封装 * @author 猫哥 * @date 2017.4.27 */public class QueryParams {    /**     * 内容     */    private StringBuilder suffix=new StringBuilder();    /**     * 编码     */    private String code;    public QueryParams(){        this.code="UTF-8";    }    public QueryParams(String code){        this.code=code;    }    public void add(String name,String value){        suffix.append("&");        try {            suffix.append(URLEncoder.encode(name,code));            suffix.append("=");            suffix.append(URLEncoder.encode(value,code));        } catch (UnsupportedEncodingException e) {            //记录下日志        }    }    @Override    public String toString(){        return suffix.toString();    }}

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