ajax代理模式跨域发送请求

前端代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>代理模式发送ajax请求</title>
</head>
<body>

<script type="text/javascript">
    window.onload = function () {
        document.getElementById("btn").onclick = function () {
            //发送ajax请求
            //1.创建对象
            var xhr = new XMLHttpRequest();
            //2.注册回调函数
            xhr.onreadystatechange = function () {
                if (xhr.readyState == 4) {
                    if (xhr.status == 200) {
                        document.getElementById("mydiv").innerHTML = this.responseText;
                    }
                }

            }
            //3.打开通道
            xhr.open("GET", "/a/proxy", true);
            //4.发送请求
            xhr.send();

        }
    }
</script>

<button id="btn">代理模式发送ajax请求</button>
<div id="mydiv"></div>
</body>

</html>

代理类

package com.wpc.javaweb;


import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


/**
 * @author 一介草莽子
 * version 1.0
 */
@SuppressWarnings({"all"})
@WebServlet("/proxy")
public class ProxyAjax extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 通过httpclient组件，发送HTTP GET请求，访问 TargetServlet
        HttpGet httpGet = new HttpGet("http://localhost:8081/b/target");
        httpGet.setHeader("Content-Type", "application/x-www-form-urlencoded");
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpResponse resp = httpClient.execute(httpGet);
        HttpEntity entity = resp.getEntity();
        BufferedReader reader = new BufferedReader(new InputStreamReader(entity.getContent(), "UTF-8"));
        String line = null;
        StringBuffer responseSB = new StringBuffer();
        while ((line = reader.readLine()) != null) {
            responseSB.append(line);
        }
        reader.close();
        httpClient.close();
        // b站点响应回来的数据
        response.getWriter().print(responseSB);
    }
}

目标类

package com.wpc.javaweb;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

/**
 * @author 一介草莽子
 * version 1.0
 */
@SuppressWarnings({"all"})
@WebServlet("/target")
public class TargetAjax extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().print("{\"name\":\"我是你爹\"}");
    }
}

ajax代理模式跨域发送请求

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