迅速配置屬於自己的過濾器。
先從JSP的編碼入手,開發編碼filter。
步驟一:在web.xml上添加<filter>,代碼如下。
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>encodeFilter</filter-name>
<filter-class>com.demo.filter.EncodeFilter</filter-class>
<init-param>
<param-name>encode</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>ignore</param-name>
<param-value>false</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodeFilter</filter-name>
<url-pattern>/*</url-pattern> <!-- "/*"即對所有的請求進行過濾 -->
</filter-mapping>
上面的配置的filter,路徑爲com.demo.filter.EncodeFilter,命名encodeFilter,映射過濾文件爲/*(即全部過濾)。另外在定義filter時,初始化了兩個參數:encode、ignore,兩個參數在xml裏面配置然後由後臺Filter類應用,前者賦值爲編碼方式utf-8,後者賦值false即是否開啓過濾。再看看後臺類的實現。
package com.demo.filter;
import java.io.IOException;
import java.util.Enumeration;
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.HttpServletRequest;
/*
* 設置傳值編碼:UTF-8
*/
public class EncodeFilter implements Filter {
private String encode = null;
private boolean ignore = false;
public void init(FilterConfig filterConfig) throws ServletException {
String encode = filterConfig.getInitParameter("encode");
String ignore = filterConfig.getInitParameter("ignore");
if (this.encode == null)
this.encode = encode;
if ("1".equals(ignore) || "true".equals(ignore)) {
this.ignore = true;
}
}
public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
if (!ignore) {
if (null == request.getCharacterEncoding()) {
request.setCharacterEncoding(encode);
}
}
chain.doFilter(request,response);
}
public void destroy() {
encode = null;
ignore = false;
}
}
可以看到,本類EncodeFilter繼承了父類Filter(抽象類),要求實現父類的三個方法:init(FilterConfig filterConfig)、doFilter(ServletRequest request, ServletResponse response,FilterChain chain)、destroy(),如EncodeFilter類的三個成員方法就是了。結合前面配置的web.xml,很快就上手了。