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通过过滤器控制页面输出内容

發布時間：2025/3/20 编程问答 22 豆豆

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在打開的頁面中彈出一個對話框，可通過過濾器來控制頁面輸出的內容，進行實現在每個響應的頁面中都彈出一個對話框的功能

在完成過濾任務時，將請求的對象返回到自定義的應答對象中，通過自定義應答對象對請求的數據進行編譯，編譯完成后通過自定義的方法返回響應數據，通過replace()方法向響應的數據中添加調用彈出對象框的代碼：

replace()方法:將方法中的newChar替換指定字符串中出現的所有oldChar public String replace(char oldChar,char newChar)

創建OutputStream.java文件繼承ServletOutputStream類，替換父類的輸出流

public class OutputStream extends ServletOutputStream {ByteArrayOutputStream stream; //創建字節數組輸出流@Overridepublic boolean isReady() {return false;}@Overridepublic void setWriteListener(WriteListener arg0) {}public OutputStream(ByteArrayOutputStream stream){ //構造方法初始化輸出流this.stream=stream;}@Overridepublic void write(int b) throws IOException {stream.write(b); //使用此類的輸出流替換父類的輸出方法 }}

創建ResponseWrapper.java文件繼承HttpServletResponseWrapper，使響應對象進行重新編譯并返回響應的數據

public class ResponseWrapper extends HttpServletResponseWrapper {private OutputStream stream; //聲明一個輸出流private ByteArrayOutputStream byteStream; //聲明字節數組輸出流private PrintWriter pw; //聲明打印輸出流public ResponseWrapper(HttpServletResponse response) {super(response);byteStream=new ByteArrayOutputStream(); //數據流初始化stream=new OutputStream(byteStream);pw=new PrintWriter(byteStream);}public ServletOutputStream getOutputStream()throws IOException{return stream; //返回字節輸出流并重寫父類方法}public PrintWriter getWriter()throws IOException{return pw; //返回打印輸出流重寫父類方法}public String getContent()throws UnsupportedEncodingException{return byteStream.toString(); //返回響應數據}}

創建過濾器的實現類OutFilter，在doFilter()方法中完成對過濾器的操作，并用getContent()獲取到響應的數據，用replace()方法將彈出對話框的代碼層加到response響應的數據中

public class OutFilter implements Filter {private boolean variable=true; //如果variable為真，每次都生成HTML首頁private FilterConfig filterConfig=null;@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)throws IOException, ServletException {HttpServletResponse httpResp=(HttpServletResponse) response;ResponseWrapper responseWrapper=new ResponseWrapper(httpResp);chain.doFilter(request, responseWrapper); //過濾器操作PrintWriter out=response.getWriter(); //創建輸出流responseWrapper.getWriter().flush(); //獲取輸出流并強制刷新String str=responseWrapper.getContent();String stres="</head><script>window.open('message.html','','width='+300+',height='+180+',top='+'+window.screen.width-300+'+',left='+'+window.screen.height+180+');</script>";out.println(str.replace("</head>", stres));}public void log(String msg){filterConfig.getServletContext().log(msg);}@Overridepublic void init(FilterConfig arg0) throws ServletException {this.filterConfig=filterConfig;}}

創建CharacterEncodingFilter.java文件

public class CharacterEncodingFilter implements Filter{protected String encoding = null;protected FilterConfig filterConfig = null;public void init(FilterConfig filterConfig) throws ServletException {this.filterConfig = filterConfig;this.encoding = filterConfig.getInitParameter("encoding");}public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {if (encoding != null) {request.setCharacterEncoding(encoding);response.setContentType("text/html; charset="+encoding);}chain.doFilter(request, response);}public void destroy() {this.encoding = null;this.filterConfig = null;} }

index.jsp頁

<%@page contentType="text/html; charset=gbk"%> <html><head><meta http-equiv="Content-Type" content="text/html; charset=gbk"><title>通過過濾器控制頁面輸出內容</title><style type="text/css"></style></head><body><div style="width:151px;height:80px;overflow:auto"><table width="123" height="74" ><tr><td height="70" class="STYLE1" align="center"><a href="indexsure.jsp">單擊刷新</a></td></tr></table></div><table width="995" height="666" border="0" align="center" cellpadding="0" cellspacing="0" background="images/main.jpg"><tr><td> </td></tr></table></body> </html>

彈出框message.html

<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> sss </body> </html>

web.xml文件配置

<filter><filter-name>CharacterEncodingFilter</filter-name><filter-class>com.cn.zj.Filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>GBK</param-value></init-param></filter><filter><filter-name>outFilter</filter-name><filter-class>com.cn.zj.Filter.OutFilter</filter-class></filter><filter-mapping><filter-name>CharacterEncodingFilter</filter-name><url-pattern>/*</url-pattern><dispatcher>REQUEST</dispatcher><dispatcher>FORWARD</dispatcher></filter-mapping><filter-mapping><filter-name>outFilter</filter-name><url-pattern>/index.jsp</url-pattern><dispatcher>REQUEST</dispatcher><dispatcher>FORWARD</dispatcher></filter-mapping><filter-mapping><filter-name>outFilter</filter-name><url-pattern>/indexsure.jsp</url-pattern><dispatcher>REQUEST</dispatcher><dispatcher>FORWARD</dispatcher></filter-mapping><session-config><session-timeout>30</session-timeout></session-config><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list><login-config><auth-method>BASIC</auth-method></login-config>

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