从servlet返回JSON [英] Return JSON from servlet
问题描述
这是一个非常基本的请求 - 响应测试。浏览器使用jQuery $ .ajax API将hello from browser发送到servlet，servlet接收此消息，然后使用org.json.simple库创建一个JSON对象，并向浏览器发送一条消息hello from server的JSON响应。
It is a very basic request-response test. Browser sends "hello from browser" to servlet using jQuery $.ajax API, and servlet receives this message, then create a JSON object using org.json.simple library and sends back to browser a JSON response with message "hello from server".
我在localhost上运行它，假设我的IP地址是123.123.12.123，平台是Ubuntu，服务器是Tomcat 6.0，在Eclipse IDE中运行。
I am running this on localhost and just assume my IP address is 123.123.12.123, the platform is Ubuntu, server is Tomcat 6.0, running in the Eclipse IDE.
测试1.我从Eclipse启动服务器，打开Firefox，输入 http：// localhost：8080 / myproject / test.jsp ，我可以看到servlet收到消息，浏览器收到响应，测试通过。
Test 1. I start the server from Eclipse, open Firefox, enter http://localhost:8080/myproject/test.jsp, I can see servlet receives message and browser receives response, test passed.
测试2.服务器仍然在Ubuntu的Eclipse上运行，我从VirtualBox启动Windows 7客户机和Windows 7中的Firefox浏览器，输入 http://123.123.12.123:8080/myproject/test.jsp ，工作按照我的预期，测试通过。
Test 2. server is still running at the Eclipse at Ubuntu, I start Windows 7 guest machine from VirtualBox and the Firefox browser in the Windows 7, enter http://123.123.12.123:8080/myproject/test.jsp, works as I expected, test passed.
测试3.服务器仍然在Eclipse上运行，在Ubuntu，打开Internet Explorer 9浏览器，给它地址 http://123.123.12.123:8080/myproject/test.jsp ，没有任何反应。
调试给了我
Test 3. server is still running at Eclipse at Ubuntu, open Internet Explorer 9 browser, give it address http://123.123.12.123:8080/myproject/test.jsp, nothing happens. The debug gives me
响应HTTP / 1.1 200 OK
Response HTTP/1.1 200 OK
响应正文{消息：你好，来自服务器}
Response body {"message":"hello from server"}
test.jsp是
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.js" type="text/javascript"></script>
<script type="text/javascript" src="release/js/libs/json2.js"></script>
<script>
$(document).ready(function(){
var request = ({"message":'Hello from browser'});
var jsonobj=JSON.stringify(request);
$.ajax({
data: {para:jsonobj},
dataType: 'json',
url: './TestServlet',
type: 'POST',
success: function(jsonObj){
alert(jsonObj.message);
},
error: function() {
alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
}
});
});
</script>
<body>
</body>
</html>
servlet代码是
The servlet code is
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.json.simple.JSONObject;
import org.json.simple.JSONValue;
/**
* Servlet implementation class TestServlet
*/
public class TestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TestServlet() {
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf8");
response.setCharacterEncoding("utf8");
response.setContentType("application/json");
PrintWriter out = response.getWriter();
JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para"));
System.out.println(jsonObj.get("message"));
JSONObject obj = new JSONObject();
obj.put("message", "hello from server");
out.print(obj);
}
}
更新：
仔细观察后的变化
error: function() {
alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
}
到
error: function(xhr,err) {
alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
}
我得到警报readyState：0和状态：0。
但我可以在Response body看到{message：hello from server}和
响应头是
I got alert readyState:0 and status:0. But I can see {"message":"hello from server"} at Response body and the response header is
Key Value
Response HTTP/1.1 200 OK
推荐答案
IE缓存AJAX请求积极（不仅仅是Firefox，Chrome和Safari）。
有时你需要在请求时设置缓存头控制器。像 cache：false 。我试图像这样修复你的代码
IE caches AJAX requests aggressively (more than Firefox, Chrome, and Safari, anyway).
Sometimes you need to set cache header controller when request. Like cache:false. I tried to fix your code like this
request.setCharacterEncoding("utf8");
//response.setCharacterEncoding("utf8");
response.setContentType("application/json");
PrintWriter out = response.getWriter();
JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para"));
System.out.println(jsonObj.get("message"));
JSONObject obj = new JSONObject();
obj.put("message", "hello from server");
out.print(obj);
我从 application / json更改了你的响应内容类型; charset = utf8 只需 application / json 就行了。
这篇关于从servlet返回JSON的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
