将异常从servlet转发到jsp页面的好方法是什么？ [英] What is the good approach to forward the exception from servlets to a jsp page?

问题描述

我知道我可以把这些东西放在web.xml中，像这样

I know I can put something in the web.xml like this

<error-page>  
   <exception-type>java.lang.Throwable</exception-type>  
   <location>/error.jsp</location>  
</error-page>

然而，jsp页面不会显示任何有创意的信息，因为它不会得到什么是异常是。我知道我们可以通过各种异常类型将不同的异常转发到不同的页面，但是在web.xml中写得太多了。我希望一个页面是足够的，另一个页面处理像404这样的错误。

However the jsp page won't show any contructive information since it won't get what exactly the exception is. I know we can have different exceptions forwarded to different pages by various exception-type but that's too much to write in web.xml. I hope one page is enough and another for handling errors like 404.

那么我应该如何将异常信息传递给jsp页面？使用会话？

So how should I pass the exception information to the jsp page? Use session?

理想情况可能是页面获取异常信息，并显示一些相关消息，而不会向用户显示异常。相反，它可以将其记录到一个文件中以备将来参考。实现这一目标的最佳方法是什么？谢谢。

The ideal situation might be the page gets the exception info and show some relevant messages about it without revealing the exception to the users. Instead it could log it into a file for future reference. What is the best approach to achieve this? Thanks.

推荐答案

有关异常的信息是已经可以由几个请求属性使用。您可以在 RequestDispatcher javadoc ：

The information about the exception is already available by several request attributes. You can find the names of all those attributes in the RequestDispatcher javadoc:

• ERROR_EXCEPTION - javax.servlet.error.exeption


• ERROR_EXCEPTION_TYPE - javax.servlet。 error.exception_type


• ERROR_MESSAGE - javax.servlet.error.message


• ERROR_REQUEST_URI - javax.servlet.error。 request_uri


• ERROR_SERVLET_NAME - javax.servlet.error.servlet_name


• ERROR_STATUS_CODE - javax.servlet.error.status_code

• ERROR_EXCEPTION - javax.servlet.error.exeption
• ERROR_EXCEPTION_TYPE - javax.servlet.error.exception_type
• ERROR_MESSAGE - javax.servlet.error.message
• ERROR_REQUEST_URI - javax.servlet.error.request_uri
• ERROR_SERVLET_NAME - javax.servlet.error.servlet_name
• ERROR_STATUS_CODE - javax.servlet.error.status_code

简而言之，这个JSP示例应该显示所有可能的异常细节：

So, in a nutshell, this JSP example should display all the possible exception detail:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
...
<ul>
    <li>Exception: <c:out value="${requestScope['javax.servlet.error.exception']}" /></li>
    <li>Exception type: <c:out value="${requestScope['javax.servlet.error.exception_type']}" /></li>
    <li>Exception message: <c:out value="${requestScope['javax.servlet.error.message']}" /></li>
    <li>Request URI: <c:out value="${requestScope['javax.servlet.error.request_uri']}" /></li>
    <li>Servlet name: <c:out value="${requestScope['javax.servlet.error.servlet_name']}" /></li>
    <li>Status code: <c:out value="${requestScope['javax.servlet.error.status_code']}" /></li>
</ul>

此外，您还可以显示这些有用的信息：

Additionally, you could also show this useful information:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<jsp:useBean id="date" class="java.util.Date" />
...
<ul>
    <li>Timestamp: <fmt:formatDate value="${date}" type="both" dateStyle="long" timeStyle="long" /></li>
    <li>User agent: <c:out value="${header['user-agent']}" /></li>
</ul>

具体的异常实例本身在JSP仅作为错误页面标记为 $ {exception}

The concrete Exception instance itself is in the JSP only available as ${exception} when you mark the page as an error page:

<%@ page isErrorPage="true" %>
...
${exception}

只有当你使用EL 2.2或更新版本，则可以打印其堆栈跟踪如下：

Only if you're using EL 2.2 or newer, then you can print its stacktrace as below:

<%@ page isErrorPage="true" %>
...
<pre>${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}</pre>

或者如果您尚未使用EL 2.2，那么请创建一个自定义EL功能：

Or if you're not on EL 2.2 yet, then create a custom EL function for that:

public final class Functions {

    private Functions() {}

    public static String printStackTrace(Throwable exception) {
        StringWriter stringWriter = new StringWriter();
        exception.printStackTrace(new PrintWriter(stringWriter, true));
        return stringWriter.toString();
    }

}

哪些在 /WEB-INF/functions.tld ：

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">

    <display-name>Custom Functions</display-name>    
    <tlib-version>1.0</tlib-version>
    <uri>http://example.com/functions</uri>

    <function>
        <name>printStackTrace</name>
        <function-class>com.example.Functions</function-class>
        <function-signature>java.lang.String printStackTrace(java.lang.Throwable)</function-signature>
    </function>
</taglib>

可以用作

<%@ taglib prefix="my" uri="http://example.com/functions" %>
...
<pre>${my:printStackTrace(exception)}</pre>

对于异常记录，最简单的地方是filter ，其映射在 / * 的URL模式上，基本上如下： p>

As to the logging of the exception, easiest place would be a filter which is mapped on an URL pattern of /* and does basically the following:

try {
    chain.doFilter(request, response);
} catch (ServletException e) {
    log(e.getRootCause());
    throw e;
} catch (IOException e) { // If necessary? Usually not thrown by business code.
    log(e);
    throw e;
}

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