servlet处理异常的方式可以自定义一个servlet进行处理异常，例如自定义ErrorServlt处理异常。
ErrorServlet在web.xml的配置方式与其他servlet相同，如下代码：
<servlet>
<servlet-name>ErrorHandler</servlet-name>
<servlet-class>ErrorHandler</servlet-class> //具体到工程中，要写清楚具体的包名
</servlet>
<servlet-mapping>
<servlet-name>ErrorHandler</servlet-name>
<url-pattern>/ErrorHandler</url-pattern>
</servlet-mapping>
//错误页面 无论什么错误都交于ErrorHandler处理
<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/ErrorHandler</location>
</error-page>
在此也可自定义处理各种错误类型的页面
<!--error-code-->
<error-page>
<error-code>404</error-code>
<location>/ErrorHandler</location>
</error-apage>
<error-page>
<error-code>403</error-code>
<location>/ErrorHandler</location>
</error-apage>
<!--exception-type-->
<error-page>
<exception-type>
javax.servlet.ServletException
</exception-type>
<location>/ErrorHandler</location>
</error-page>
<error-page>
<exception-type>
java.io.IOException
</exception-type>
<location>/ErrorHandler</location>
</error-page>
servlet异常的属性主要有以下几种:status_code(Integer),exception_type(java.lang.Class),message(String),reuest_uri(String),exception(Throwable),servlet_name(String)
其中Throwable 主要包括error异常和Exception异常。
程序实例如下：
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.util.*;// 扩展 HttpServlet 类public class ErrorHandler extends HttpServlet {
// 处理 GET 方法请求的方法
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
// 分析 Servlet 异常
Throwable throwable = (Throwable)
request.getAttribute("javax.servlet.error.exception");
Integer statusCode = (Integer)
request.getAttribute("javax.servlet.error.status_code");
String servletName = (String)
request.getAttribute("javax.servlet.error.servlet_name");
if (servletName == null){
servletName = "Unknown";
}
String requestUri = (String)
request.getAttribute("javax.servlet.error.request_uri");
if (requestUri == null){
requestUri = "Unknown";
}
// 设置响应内容类型
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Error/Exception Information";
String docType =
"<!doctype html public \"-//w3c//dtd html 4.0 " +
"transitional//en\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f0f0f0\">\n");
if (throwable == null && statusCode == null){
out.println("<h2>Error information is missing</h2>");
out.println("Please return to the <a href=\"" +
response.encodeURL("http://localhost:8080/") +
"\">Home Page</a>.");
}else if (statusCode != null){
out.println("The status code : " + statusCode);
}else{
out.println("<h2 class="tutheader">Error information</h2>");
out.println("Servlet Name : " + servletName +
"</br></br>");
out.println("Exception Type : " +
throwable.getClass( ).getName( ) +
"</br></br>");
out.println("The request URI: " + requestUri +
"<br><br>");
out.println("The exception message: " +
throwable.getMessage( ));
}
out.println("</body>");
out.println("</html>");
}
// 处理 POST 方法请求的方法
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}}
