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 ：

 

 

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：

 

package com.sumscope.cdh.api.interceptor;

import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;


public class CrossFilter implements Filter {
    private static final boolean debug = true;
    private FilterConfig filterConfig = null;

    public CrossFilter() {
        super();
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        if (filterConfig != null) {
            if (debug) {
                log("CrossFilter:Initializing filter");
            }
        }

    }

     @Override
    public String toString() {
        if (filterConfig == null) {
            return ("CrossFilter()");
        }
        StringBuffer sb = new StringBuffer("CrossFilter(");
        sb.append(filterConfig);
        sb.append(")");
        return (sb.toString());
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        if (debug) {
            log("CrossFilter:doFilter()");
        }

         if(response instanceof HttpServletResponse){
             HttpServletResponse alteredResponse = ((HttpServletResponse)response);
            // I need to find a way to make sure this only gets called on 200-300 http responses
            // TODO: see above comment
             addHeadersFor200Response(alteredResponse);
         }
         doBeforeProcessing(request, response);

         Throwable problem = null;
         try {
             chain.doFilter(request, response);
         } catch (Throwable t) {
             // If an exception is thrown somewhere down the filter chain,
             // we still want to execute our after processing, and then
             // rethrow the problem after that.
             problem = t;
             t.printStackTrace();
         }

         doAfterProcessing(request, response);

         // If there was a problem, we want to rethrow it if it is
         // a known type, otherwise log it.
         if (problem != null) {
             if (problem instanceof ServletException) {
                 throw (ServletException) problem;
             }
             if (problem instanceof IOException) {
                 throw (IOException) problem;
             }
             sendProcessingError(problem, response);
         }


    }

    @Override
    public void destroy() {

    }

    private void doBeforeProcessing(ServletRequest request, ServletResponse response)
            throws IOException, ServletException {
        if (debug) {
            log("CrossFilter:DoBeforeProcessing");
        }

    }

    private void doAfterProcessing(ServletRequest request, ServletResponse response)
            throws IOException, ServletException {
        if (debug) {
            log("CrossFilter:DoAfterProcessing");
        }
    }

    private void addHeadersFor200Response(HttpServletResponse response){
        //TODO: externalize the Allow-Origin
        response.addHeader("Access-Control-Allow-Origin", "*");
        response.addHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE, HEAD");
        response.addHeader("Access-Control-Allow-Headers", "X-PINGOTHER, Origin, X-Requested-With, Content-Type, Accept");
        response.addHeader("Access-Control-Max-Age", "1728000");
    }

    private void sendProcessingError(Throwable t, ServletResponse response) {
        String stackTrace = getStackTrace(t);

        if (stackTrace != null && !stackTrace.equals("")) {
            try {
                response.setContentType("text/html");
                PrintStream ps = new PrintStream(response.getOutputStream());
                PrintWriter pw = new PrintWriter(ps);
                pw.print("<html>\n<head>\n<title>Error</title>\n</head>\n<body>\n"); //NOI18N

                // PENDING! Localize this for next official release
                pw.print("<h1>The resource did not process correctly</h1>\n<pre>\n");
                pw.print(stackTrace);
                pw.print("</pre></body>\n</html>"); //NOI18N
                pw.close();
                ps.close();
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        } else {
            try {
                PrintStream ps = new PrintStream(response.getOutputStream());
                t.printStackTrace(ps);
                ps.close();
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        }
    }

    public static String getStackTrace(Throwable t) {
        String stackTrace = null;
        try {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            t.printStackTrace(pw);
            pw.close();
            sw.close();
            stackTrace = sw.getBuffer().toString();
        } catch (Exception ex) {
        }
        return stackTrace;
    }

    public void log(String msg) {
        filterConfig.getServletContext().log(msg);
    }


}

在Web.xml配置域名访问过滤器

 

 

 <filter>
    <filter-name>crossFilter</filter-name>
   <filter-class>com.sumscope.cdh.api.interceptor.CrossFilter</filter-class>
 </filter>
<filter-mapping>
   <filter-name>crossFilter</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>