Java 发起http GET POST请求示例-原创手记-慕课网

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。

另外，关于编码的部分尤其需要注意，编码的原理较为复杂，就不再具体解释了。

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("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        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("  </BODY>");
        out.println("</HTML>");
        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("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        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("  </BODY>");
        out.println("</HTML>");
        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();
    }
}

Over!

Java 发起http GET POST请求示例原创