java web设置过滤器

最新推荐文章于 2024-11-04 21:59:20 发布

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本文介绍了一个简单的编码过滤器示例，该过滤器用于设置请求和响应的字符编码为UTF-8。文章详细记录了由于web.xml文件中配置错误导致的问题及解决过程。

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今天在写一个编码过滤器demo的时候，写了一个特别简单的例子。

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 EncodeFilterTest implements Filter {
	private String encoding;

	public void destroy() {

	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		request.setCharacterEncoding(encoding);
		response.setCharacterEncoding(encoding);
		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.encoding = filterConfig.getInitParameter("encoding");
	}

}

web.xml

<servlet>
  		<servlet-name>EncodeFilterTest</servlet-name>
  		<servlet-class>com.encoding.EncodeFilterTest</servlet-class>
  		<init-param>
  			<param-name>encoding</param-name>
  			<param-value>utf-8</param-value>
  		</init-param>
	  </servlet>
	  <servlet-mapping>
	  		<servlet-name>EncodeFilterTest</servlet-name>
	  		<url-pattern>/*</url-pattern>
	  </servlet-mapping>

结果一直报错：

严重: Allocate exception for servlet EncodeFilterTest
java.lang.ClassCastException: com.encoding.EncodeFilterTest cannot be cast to javax.servlet.Servlet
	at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1146)
	at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:866)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)

网上查了好多，貌似没有人发生类似问题。

解决方法：自己web.xml中写错了，将<filter>写成了<servlet>

正确写法是：

<filter>
		<filter-name>EncodeFilterTest</filter-name>
		<filter-class>com.encoding.EncodeFilterTest</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>utf-8</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>EncodeFilterTest</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>