AJAX跨域代理机制实现原理解析------AJAX

package com.bjpowernode.httpClient;

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.InputStreamReader;

public class httpClientSendGet {
    public static void main(String args[]) throws Exception {
        String channelId = "sdd";
        String clientId = "123";
        // 目标地址
//        String url = "http://XXX.XXX.com.cn/arowana/channel/getChannelLine?channelId=" + channelId + "&clientId=" + clientId;
        String url = "http://localhost:8081/Test/hello";
        HttpGet httpGet = new HttpGet(url);
        // 设置类型 "application/x-www-form-urlencoded" "application/json"
        httpGet.setHeader("Content-Type", "application/x-www-form-urlencoded");
        System.out.println("调用URL: " + httpGet.getURI());//        httpClient实例化
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 执行请求并获取返回
        HttpResponse response = httpClient.execute(httpGet);//
        System.out.println("Response toString()" + response.toString());
        HttpEntity entity = response.getEntity();
        System.out.println("返回状态码：" + response.getStatusLine());
        //得到返回数据的长度；没有该参数返回-1//
        if (entity != null)
        {
            System.out.println("返回消息内容长度: " + entity.getContentLength());
        }
        // 显示结果
        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);
        }
        System.out.println("返回消息：" + responseSB);
        reader.close();
        httpClient.close();
    }
}

package com.bjpowernode.httpClient;

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.InputStreamReader;

public class httpClientSendGet {
    public static void main(String args[]) throws Exception {
        String channelId = "sdd";
        String clientId = "123";
        // 目标地址
//        String url = "http://XXX.XXX.com.cn/arowana/channel/getChannelLine?channelId=" + channelId + "&clientId=" + clientId;
        String url = "http://localhost:8081/Test/hello";
        HttpGet httpGet = new HttpGet(url);
        // 设置类型 "application/x-www-form-urlencoded" "application/json"
        httpGet.setHeader("Content-Type", "application/x-www-form-urlencoded");
        System.out.println("调用URL: " + httpGet.getURI());//        httpClient实例化
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 执行请求并获取返回
        HttpResponse response = httpClient.execute(httpGet);//
        System.out.println("Response toString()" + response.toString());
        HttpEntity entity = response.getEntity();
        System.out.println("返回状态码：" + response.getStatusLine());
        //得到返回数据的长度；没有该参数返回-1//
        if (entity != null)
        {
            System.out.println("返回消息内容长度: " + entity.getContentLength());
        }
        // 显示结果
        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);
        }
        System.out.println("返回消息：" + responseSB);
        reader.close();
        httpClient.close();
    }
}

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;

@WebServlet("/hello")
public class Hello extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //设置响应头
//        response.setHeader("Access-Control-Allow-Origin","http://localhost:8080");
        //跨域访问的资源允许访问,设置响应头的方式原理是

        response.getWriter().println("{\"username\" : \"zhangSan\"};");
    }
}

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;

@WebServlet("/hello")
public class Hello extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //设置响应头
//        response.setHeader("Access-Control-Allow-Origin","http://localhost:8080");
        //跨域访问的资源允许访问,设置响应头的方式原理是

        response.getWriter().println("{\"username\" : \"zhangSan\"};");
    }
}