过滤器中向所有JSP页面插入html代码

最新推荐文章于 2024-07-31 11:05:25 发布

BearRui

最新推荐文章于 2024-07-31 11:05:25 发布

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分类专栏： Java 文章标签： html jsp buffer 框架 null mvc

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本文介绍了一种在MVC框架中向所有JSP页面<head>标签内自动添加JS引用的方法。通过自定义PageResponseWrapper类继承HttpServletResponseWrapper，并结合过滤器实现对响应内容的修改，确保所有页面都能包含特定的JS文件。

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为公司内部开发了1个简单的MVC框架，框架中需要向所有JSP页面的<head>中插入2条引用JS的代码，实现如下：

主要是继承HttpServletResponseWrapper写1个类(PageResponseWrapper),代码：

1 public class PageResponseWrapper extends HttpServletResponseWrapper {
2     private Buffer buffer;
3     private HttpServletResponse originalResponse;
4
5     public PageResponseWrapper(final HttpServletResponse response){
6         super(response);
7         this.originalResponse = response;
8         buffer = new Buffer();
9     }
10
11     @Override
12     public PrintWriter getWriter() throws IOException {
13         return buffer.getWriter();
14     }
15
16     public CharArrayWriter getContent(){
17         return buffer.getBufferedWriter();
18     }
19
20     public void close() throws IOException {
21         buffer.getWriter().close();
22     }
23
24     public void finalize() throws Throwable {
25        super.finalize();
26        buffer.getWriter().close();
27     }
28
29     /**
30      * 获取原始的response
31      * @return the originalResponse
32      */
33     public HttpServletResponse getOriginalResponse() {
34         return originalResponse;
35     }
36 }

Buffer类:

1 public class Buffer {
2
3     private CharArrayWriter bufferedWriter;
4     private PrintWriter exposedWriter;
5
6     public char[] getContents() throws IOException {
7         //bufferedWriter 表示请求的页面的html
8         if (getBufferedWriter() != null) {
9             return getBufferedWriter().toCharArray();
10         }
11         return null;
12     }
public PrintWriter getWriter() {
16         if (getBufferedWriter() == null) {
17             bufferedWriter = new CharArrayWriter();
18             exposedWriter = new PrintWriter(getBufferedWriter());
19         }
20         return exposedWriter;
21     }
22     /**
23      * @return the bufferedWriter
24      */
25     public CharArrayWriter getBufferedWriter() {
26         return bufferedWriter;
27     }
28 }

过滤器的代码:

1 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
2     HttpServletRequest hRequest = (HttpServletRequest)request;
3     HttpServletResponse hResponse = (HttpServletResponse)response;
4     PageResponseWrapper prw = new PageResponseWrapper(hResponse);
5
6     chain.doFilter(request, prw);
7     // 得到视图html代码
8     String tmpHtml = prw.getContent();
9     // 最终输出的html代码
10     String retHtml = "";
11     // 查找<head>
12     int index = tmpHtml.toLowerCase().indexOf("<head>");
13     if(index != -1){
14         index +=6;
15         retHtml = tmp.substring(0, index) + "<script src='http://./..js'></script>" + tmp.substring(index);
16     }else{
17         retHtml = tmpHtml;
18     }
19     // 输出(注意，这里只能使用hResponse，不能使用prwgetWriter())
20     PrintWriter writer = hResponse.getWriter();
21     writer.write(retHtml);
22     writer.close();
23     writer.close();
24     writer.flush();
25 }