Ajax访问Restful API跨域解决方案

最近开发API接口时，用Ajax调用远程服务上API的接口时，出现以下错误 ：

 

 

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1. XMLHttpRequest cannot load http://192.168.1.101:8080/CDHAPI/bond/quote/minutely/1m/112188.SZ. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.  

产生此种问题是由于Ajax跨域限制而引起的问题。Access-Control-Allow-Origin是HTML5中定义的一种服务器端返回Response header，用来解决资源（比如字体）的跨域权限问题。它定义了该资源允许被哪个域引用，或者被所有域引用。

 

根据这个思路，在服务端返回时在响应体的添加Header，设置Access-Control-Allow-Origin允许可访问的域。具体工作如下：

（1）写一个过滤器，在Reponse中Header中设置Access-Control-Allow-Origin：代码如下：

 

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1. package com.sumscope.cdh.api.interceptor;  
2.   
3. import java.io.IOException;  
4. import java.io.PrintStream;  
5. import java.io.PrintWriter;  
6. import java.io.StringWriter;  
7.   
8. import javax.servlet.Filter;  
9. import javax.servlet.FilterChain;  
10. import javax.servlet.FilterConfig;  
11. import javax.servlet.ServletException;  
12. import javax.servlet.ServletRequest;  
13. import javax.servlet.ServletResponse;  
14. import javax.servlet.http.HttpServletResponse;  
15.   
16.   
17. public class CrossFilter implements Filter {  
18.     private static final boolean debug = true;  
19.     private FilterConfig filterConfig = null;  
20.       
21.     public CrossFilter() {  
22.         super();  
23.     }  
24.   
25.     @Override  
26.     public void init(FilterConfig filterConfig) throws ServletException {  
27.         this.filterConfig = filterConfig;  
28.         if (filterConfig != null) {  
29.             if (debug) {                  
30.                 log("CrossFilter:Initializing filter");  
31.             }  
32.         }  
33.   
34.     }  
35.       
36.      @Override  
37.     public String toString() {  
38.         if (filterConfig == null) {  
39.             return ("CrossFilter()");  
40.         }  
41.         StringBuffer sb = new StringBuffer("CrossFilter(");  
42.         sb.append(filterConfig);  
43.         sb.append(")");  
44.         return (sb.toString());  
45.     }  
46.   
47.     @Override  
48.     public void doFilter(ServletRequest request, ServletResponse response,  
49.             FilterChain chain) throws IOException, ServletException {  
50.         if (debug) {  
51.             log("CrossFilter:doFilter()");  
52.         }  
53.   
54.          if(response instanceof HttpServletResponse){  
55.              HttpServletResponse alteredResponse = ((HttpServletResponse)response);  
56.             // I need to find a way to make sure this only gets called on 200-300 http responses  
57.             // TODO: see above comment  
58.              addHeadersFor200Response(alteredResponse);  
59.          }  
60.          doBeforeProcessing(request, response);  
61.   
62.          Throwable problem = null;  
63.          try {  
64.              chain.doFilter(request, response);  
65.          } catch (Throwable t) {  
66.              // If an exception is thrown somewhere down the filter chain,  
67.              // we still want to execute our after processing, and then  
68.              // rethrow the problem after that.  
69.              problem = t;  
70.              t.printStackTrace();  
71.          }  
72.   
73.          doAfterProcessing(request, response);  
74.   
75.          // If there was a problem, we want to rethrow it if it is  
76.          // a known type, otherwise log it.  
77.          if (problem != null) {  
78.              if (problem instanceof ServletException) {  
79.                  throw (ServletException) problem;  
80.              }  
81.              if (problem instanceof IOException) {  
82.                  throw (IOException) problem;  
83.              }  
84.              sendProcessingError(problem, response);  
85.          }  
86.          
87.   
88.     }  
89.   
90.     @Override  
91.     public void destroy() {  
92.   
93.     }  
94.       
95.     private void doBeforeProcessing(ServletRequest request, ServletResponse response)  
96.             throws IOException, ServletException {  
97.         if (debug) {  
98.             log("CrossFilter:DoBeforeProcessing");  
99.         }  
100.   
101.     }      
102.   
103.     private void doAfterProcessing(ServletRequest request, ServletResponse response)  
104.             throws IOException, ServletException {  
105.         if (debug) {  
106.             log("CrossFilter:DoAfterProcessing");  
107.         }  
108.     }  
109.       
110.     private void addHeadersFor200Response(HttpServletResponse response){  
111.         //TODO: externalize the Allow-Origin  
112.         response.addHeader("Access-Control-Allow-Origin", "*");  
113.         response.addHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE, HEAD");  
114.         response.addHeader("Access-Control-Allow-Headers", "X-PINGOTHER, Origin, X-Requested-With, Content-Type, Accept");  
115.         response.addHeader("Access-Control-Max-Age", "1728000");  
116.     }  
117.       
118.     private void sendProcessingError(Throwable t, ServletResponse response) {  
119.         String stackTrace = getStackTrace(t);          
120.   
121.         if (stackTrace != null && !stackTrace.equals("")) {  
122.             try {  
123.                 response.setContentType("text/html");  
124.                 PrintStream ps = new PrintStream(response.getOutputStream());  
125.                 PrintWriter pw = new PrintWriter(ps);                  
126.                 pw.print("<html>\n<head>\n<title>Error</title>\n</head>\n<body>\n"); //NOI18N  
127.   
128.                 // PENDING! Localize this for next official release  
129.                 pw.print("<h1>The resource did not process correctly</h1>\n<pre>\n");                  
130.                 pw.print(stackTrace);                  
131.                 pw.print("</pre></body>\n</html>"); //NOI18N  
132.                 pw.close();  
133.                 ps.close();  
134.                 response.getOutputStream().close();  
135.             } catch (Exception ex) {  
136.             }  
137.         } else {  
138.             try {  
139.                 PrintStream ps = new PrintStream(response.getOutputStream());  
140.                 t.printStackTrace(ps);  
141.                 ps.close();  
142.                 response.getOutputStream().close();  
143.             } catch (Exception ex) {  
144.             }  
145.         }  
146.     }  
147.       
148.     public static String getStackTrace(Throwable t) {  
149.         String stackTrace = null;  
150.         try {  
151.             StringWriter sw = new StringWriter();  
152.             PrintWriter pw = new PrintWriter(sw);  
153.             t.printStackTrace(pw);  
154.             pw.close();  
155.             sw.close();  
156.             stackTrace = sw.getBuffer().toString();  
157.         } catch (Exception ex) {  
158.         }  
159.         return stackTrace;  
160.     }  
161.       
162.     public void log(String msg) {  
163.         filterConfig.getServletContext().log(msg);          
164.     }  
165.   
166.   
167. }  

在Web.xml配置域名访问过滤器

 

 

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1.  <filter>     
2.     <filter-name>crossFilter</filter-name>  
3.    <filter-class>com.sumscope.cdh.api.interceptor.CrossFilter</filter-class>  
4.  </filter>  
5. <filter-mapping>  
6.    <filter-name>crossFilter</filter-name>  
7.    <url-pattern>/*</url-pattern>  
8. </filter-mapping>