servlet解决浏览器的跨域

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概述：

在做一些web请求时，会涉及到很麻烦的浏览器跨域问题，因此，一般都会通过后台处理再给前台。本文讲述通过servlet解决浏览器的跨域问题。

实现：

在工程下新建一个servlet，实现代码如下：

package lzugis.web.agent;import java.io.BufferedInputStream;import java.io.BufferedReader;import java.io.IOException;import java.net.URL;import java.net.URLConnection;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class WebAgent */@WebServlet(name="WebAgent",urlPatterns="/web/agent")public class WebAgent extends HttpServlet {private static final long serialVersionUID = 1L;private String debug = "false";    /**     * Default constructor.      */    public WebAgent() {        // TODO Auto-generated constructor stub    }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubString encoding = getInitParameter("encoding");    if ((encoding != null) && (!"".equals(encoding))) {      request.setCharacterEncoding(encoding);    }    String url = request.getParameter("url");    if (!"".equals(url)) {      responseFile(request, response, url);      return;    }}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubString encoding = getInitParameter("encoding");    if ((encoding != null) && (!"".equals(encoding))) {      request.setCharacterEncoding(encoding);    }    String url = request.getParameter("url");    if (!"".equals(url)) {      responseFile(request, response, url);      return;    }    if ("true".equals(this.debug)) {    String data = readXMLFromRequestBody(request);    System.out.println(data);    }}public void responseFile(HttpServletRequest req, HttpServletResponse resp, String url) {    try {      URL u = new URL(url);      URLConnection urlc = u.openConnection();      urlc.setConnectTimeout(3000);      urlc.setReadTimeout(100000);      resp.setContentType(urlc.getContentType());      ServletOutputStream out = null;      BufferedInputStream input = null;      byte[] data = new byte[1024];      int length = -1;      input = new BufferedInputStream(urlc.getInputStream());      out = resp.getOutputStream();      while ((length = input.read(data)) != -1) {        out.write(data, 0, length);      }      input.close();      out.flush();      out.close();    }    catch (IOException localIOException)    {    }  }  private String readXMLFromRequestBody(HttpServletRequest request) {    StringBuffer strBuf = new StringBuffer();    try {      BufferedReader reader = request.getReader();      String line = null;      while ((line = reader.readLine()) != null)        strBuf.append(line).append("\n");    } catch (IOException e) {      e.printStackTrace();    }    return strBuf.toString();  }}

说明：

servlet是通过注解的方式配的，访问路径为：localhost:8080/lzugis/web/agent?url=http://localhost:6080/arcgis/rest/services/?f=pjson。

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