1.Filter接口的三个方法：
初始化：
public void init(FilterConfig filterConfig) throws ServletException {
}
执行过滤：
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
}
销毁：
public void destroy() {
}
2.写法：
（1）一般写法，可维护性不强
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class EncodingFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
arg0.setCharacterEncoding("UTF-8");
arg2.doFilter(arg0, arg1);
}
public void destroy() {
}
}
部分配置文件：
<filter>
<filter-name>encoding</filter-name>
<filter-class>util.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
（2）为方便后期扩展维护，可把字符集配置到配置文件中，可维护性强
import java.io.IOException;
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;
public class EncodingFilter implements Filter {
private FilterConfig config;
private String targetEncoding;
public void init(FilterConfig config) {
this.config = config;
this.targetEncoding = this.config.getInitParameter("encoding");
}
public void doFilter(ServletRequest srequest, ServletResponse sresponse,
FilterChain chain) throws IOException, ServletException {
System.out.println("encoding=" + this.targetEncoding);
HttpServletRequest request = (HttpServletRequest) srequest;
request.setCharacterEncoding(this.targetEncoding);
chain.doFilter(srequest, sresponse);
}
public void setFilterConfig(final FilterConfig filterConfig) {
}
public void destroy() {
config = null;
}
}
部分配置文件如下：
<filter>
<filter-name>encoding</filter-name>
<filter-class>util.EncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
