blocks|key|730293|text|在错误页面上，只需执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|730294|<jsp:scriptlet>
++++exception.printStackTrace(response.getWriter())
</jsp:scriptlet>|code-block|syntax|javascript|730295|尽管这回避了一个问题:用户将如何处理异常。为什么不将异常写到错误日志中，这样它就会持久存在，并且可以在用户投诉后返回到它？|730296|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

On the error page, just do:

<pre><code>&lt;jsp:scriptlet&gt;
 exception.printStackTrace(response.getWriter())
&lt;/jsp:scriptlet&gt;
</code></pre>

Although this begs the question: what is a user going to do with an exception. Why not write the exception to the error log so it is persisted and you can go back to it after a user complains?

blocks|key|513921|text|抛出的异常对象可作为名为“javax.servlet.error.ception”的请求属性。因此，在您的JSP中，您可以编写：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|513922|<%25+request.getAttribute("javax.servlet.error.exception").printStackTrace(new+java.io.PrintWriter(out);+%25>|code-block|syntax|javascript|513923|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Thrown Exception object is available as request attribute with name 'javax.servlet.error.exception'. So, in your JSP, you can write:

<pre><code>&lt;% request.getAttribute("javax.servlet.error.exception").printStackTrace(new java.io.PrintWriter(out); %&gt;
</code></pre>

blocks|key|513938|text|您可以使用jstl核心库|type|unstyled|depth|inlineStyleRanges|entityRanges|data|513939|1)在JSP文件上导入tablib|513940|<%25@+taglib+uri="http://java.sun.com/jsp/jstl/core"+prefix="c"+%25>|code-block|syntax|javascript|513941|2)使用标签|513942|<c:catch+var="myExceptionObject">
++++Code+that+might+throw+Exception
</c:catch>

<c:if+test="${myExceptionObject}+!=+null">
++++There+was+an+exception:+${myExceptionObject.message}
</c:if>|513943|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You can use jstl core library

1) Import tablib on top of JSP file

<pre><code>&lt;%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %&gt;
</code></pre>

2) use tag

<pre><code>&lt;c:catch var="myExceptionObject"&gt;
 Code that might throw Exception
&lt;/c:catch&gt;

&lt;c:if test="${myExceptionObject} != null"&gt;
 There was an exception: ${myExceptionObject.message}
&lt;/c:if&gt;
</code></pre>

blocks|key|513976|text|或者，为了避免在jsp中使用scriptlet，可以使用jstl：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|513977|<%25@taglib+prefix="c"+uri="http://java.sun.com/jsp/jstl/core"%25>
...

<c:set+var="exception"+value="${requestScope['javax.servlet.error.exception']}"/>

<c:if+test="${exception+!=+null}">
++<h4>${exception}</h4>
++<c:forEach+var="stackTraceElem"+items="${exception.stackTrace}">
++++<c:out+value="${stackTraceElem}"/> 
++</c:forEach>
</c:if>|code-block|syntax|javascript|513978|理想情况下，应该禁止将scriptlet作为最佳实践。通过web.xml配置明确阻止jsp文件中的脚本：|513979|<jsp-config>
++<jsp-property-group>
++++<url-pattern>*.jsp</url-pattern>
++++<scripting-invalid>true</scripting-invalid>
++</jsp-property-group>
</jsp-config>|513980|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Or, to avoid using scriptlets in your jsp, use jstl:

<pre><code>&lt;%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%&gt;
...

&lt;c:set var="exception" value="${requestScope['javax.servlet.error.exception']}"/&gt;

&lt;c:if test="${exception != null}"&gt;
 &lt;h4&gt;${exception}&lt;/h4&gt;
 &lt;c:forEach var="stackTraceElem" items="${exception.stackTrace}"&gt;
 &lt;c:out value="${stackTraceElem}"/&gt;&lt;br/&gt;
 &lt;/c:forEach&gt;
&lt;/c:if&gt;
</code></pre>

Ideally, scriptlets should be disallowed as a best practice. Explicitly prevent scriplets in you jsp files via the web.xml configuration:

<pre><code>&lt;jsp-config&gt;
 &lt;jsp-property-group&gt;
 &lt;url-pattern&gt;*.jsp&lt;/url-pattern&gt;
 &lt;scripting-invalid&gt;true&lt;/scripting-invalid&gt;
 &lt;/jsp-property-group&gt;
&lt;/jsp-config&gt;
</code></pre>

blocks|key|730408|text|使用JSP+scriptlet是十年来一直不赞成的做法。你最好是avoid它。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|730409|如果你已经在使用EL+2.2或更高版本(Tomcat+7%2B、JBoss+AS+6%2B、WildFly、GlassFish+3%2B等)，并且对${instance.method()}形式的方法表达式有新的支持，那么你可以只使用100%25的EL。|style|CODE|730410|首先，您需要通过JspWriter#flush()显式地刷新JSP编写器，以便将前面所有的JSP模板输出真正写入servlet响应的编写器：|730411|${pageContext.out.flush()}|code-block|syntax|javascript|730412|然后，您可以只将ServletResponse#getWriter()传递给Throwable#printStackTrace()。|730413|${exception.printStackTrace(pageContext.response.writer)}|730414|完整示例：|730415|<%25@page+pageEncoding="UTF-8"+isErrorPage="true"+%25>
...
<pre>${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}</pre>|730416|如果您已经在使用EL+3.0+(Tomcat+8%2B、WildFly、GlassFish+4%2B等)，您甚至可以使用新的分号运算符将其作为单个表达式，分号运算符用于分隔EL语句：|730417|<%25@page+pageEncoding="UTF-8"+isErrorPage="true"+%25>
...
<pre>${pageContext.out.flush();exception.printStackTrace(pageContext.response.writer)}</pre>|730418|如果由于某种原因不能使用isErrorPage="true"+(因此${exception}隐式对象不可用)，那么只需替换为${requestScope['javax.servlet.error.exception']}即可|730419|<%25@page+pageEncoding="UTF-8"+%25>
...
<pre>${pageContext.out.flush()}${requestScope['javax.servlet.error.exception'].printStackTrace(pageContext.response.writer)}</pre>|730420|如果你还没有使用EL+2.2，那么你最好的选择就是创建一个定制的EL函数。详情请访问What+is+the+good+approach+to+forward+the+exception+from+servlets+to+a+jsp+page?|730421|下面是一个更完整的错误页面示例，其中包含更多详细信息：|730422|<%25@page+pageEncoding="UTF-8"+isErrorPage="true"+%25>
<%25@taglib+uri="http://java.sun.com/jsp/jstl/core"+prefix="c"+%25>
...
<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>
++++<li>Stack+trace:+<pre>${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}</pre></li>
</ul>|730423|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3177733/how-to-avoid-java-code-in-jsp-files|1|http://docs.oracle.com/javaee/7/api/javax/servlet/jsp/JspWriter.html#flush--|2|http://docs.oracle.com/javaee/7/api/javax/servlet/ServletResponse.html#getWriter--|3|http://docs.oracle.com/javase/8/docs/api/java/lang/Throwable.html#printStackTrace-java.io.PrintWriter-|4|https://stackoverflow.com/questions/12257928/what-is-the-good-approach-to-forward-the-exception-from-servlets-to-a-jsp-page/^0|W|5|0|0|1W|K|0|8|H|8|H|1|0|0|8|R|12|R|8|R|2|12|R|3|0|0|0|0|0|0|C|I|Y|C|1Q|1C|0|0|16|27|4|0|0|0^^$0|@$1|2|3|4|5|6|7|1Q|8|@]|9|@$A|1R|B|1S|1|1T]]|C|$]]|$1|D|3|E|5|6|7|1U|8|@$A|1V|B|1W|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|1X|8|@$A|1Y|B|1Z|F|G]]|9|@$A|20|B|21|1|22]]|C|$]]|$1|J|3|K|5|L|7|23|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|24|8|@$A|25|B|26|F|G]|$A|27|B|28|F|G]]|9|@$A|29|B|2A|1|2B]|$A|2C|B|2D|1|2E]]|C|$]]|$1|Q|3|R|5|L|7|2F|8|@]|9|@]|C|$M|N]]|$1|S|3|T|5|6|7|2G|8|@]|9|@]|C|$]]|$1|U|3|V|5|L|7|2H|8|@]|9|@]|C|$M|N]]|$1|W|3|X|5|6|7|2I|8|@]|9|@]|C|$]]|$1|Y|3|Z|5|L|7|2J|8|@]|9|@]|C|$M|N]]|$1|10|3|11|5|6|7|2K|8|@$A|2L|B|2M|F|G]|$A|2N|B|2O|F|G]|$A|2P|B|2Q|F|G]]|9|@]|C|$]]|$1|12|3|13|5|L|7|2R|8|@]|9|@]|C|$M|N]]|$1|14|3|15|5|6|7|2S|8|@]|9|@$A|2T|B|2U|1|2V]]|C|$]]|$1|16|3|17|5|6|7|2W|8|@]|9|@]|C|$]]|$1|18|3|19|5|L|7|2X|8|@]|9|@]|C|$M|N]]|$1|1A|3|-4|5|6|7|2Y|8|@]|9|@]|C|$]]]|1B|$1C|$5|1D|1E|1F|C|$1G|1H]]|1I|$5|1D|1E|1F|C|$1G|1J]]|1K|$5|1D|1E|1F|C|$1G|1L]]|1M|$5|1D|1E|1F|C|$1G|1N]]|1O|$5|1D|1E|1F|C|$1G|1P]]]]

Using JSP scriptlets is a frowned upon practice since a decade. You'd best <a href="https://stackoverflow.com/questions/3177733/how-to-avoid-java-code-in-jsp-files">avoid</a> it.

If you're already on EL 2.2 or newer (Tomcat 7+, JBoss AS 6+, WildFly, GlassFish 3+, etc), with new support for method expressions of the form <code>${instance.method()}</code>, then you can just use 100% EL for this. 

First you need to explicitly flush the JSP writer via <a href="http://docs.oracle.com/javaee/7/api/javax/servlet/jsp/JspWriter.html#flush--" rel="noreferrer"><code>JspWriter#flush()</code></a>, so that all preceding JSP template output really gets written to the writer of the servlet response:

<pre class="lang-xml prettyprint-override"><code>${pageContext.out.flush()}
</code></pre>

Then you can just pass <a href="http://docs.oracle.com/javaee/7/api/javax/servlet/ServletResponse.html#getWriter--" rel="noreferrer"><code>ServletResponse#getWriter()</code></a> to <a href="http://docs.oracle.com/javase/8/docs/api/java/lang/Throwable.html#printStackTrace-java.io.PrintWriter-" rel="noreferrer"><code>Throwable#printStackTrace()</code></a>.

<pre class="lang-xml prettyprint-override"><code>${exception.printStackTrace(pageContext.response.writer)}
</code></pre>

Complete example:

<pre class="lang-xml prettyprint-override"><code>&lt;%@page pageEncoding="UTF-8" isErrorPage="true" %&gt;
...
&lt;pre&gt;${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}&lt;/pre&gt;
</code></pre>

If you're already on EL 3.0 (Tomcat 8+, WildFly, GlassFish 4+, etc), you can even make it a single expression with the new semicolon operator which separates EL statements:

<pre class="lang-xml prettyprint-override"><code>&lt;%@page pageEncoding="UTF-8" isErrorPage="true" %&gt;
...
&lt;pre&gt;${pageContext.out.flush();exception.printStackTrace(pageContext.response.writer)}&lt;/pre&gt;
</code></pre>

If you can't use <code>isErrorPage="true"</code> for some reason (and thus <code>${exception}</code> implicit object isn't available), then just substitute with <code>${requestScope['javax.servlet.error.exception']}</code>:

<pre class="lang-xml prettyprint-override"><code>&lt;%@page pageEncoding="UTF-8" %&gt;
...
&lt;pre&gt;${pageContext.out.flush()}${requestScope['javax.servlet.error.exception'].printStackTrace(pageContext.response.writer)}&lt;/pre&gt;
</code></pre>

If you're still not on EL 2.2, then your best bet is creating a custom EL function. Detail can be found in <a href="https://stackoverflow.com/questions/12257928/what-is-the-good-approach-to-forward-the-exception-from-servlets-to-a-jsp-page/">What is the good approach to forward the exception from servlets to a jsp page?</a> 

Below is a more complete error page example with more detail:

<pre class="lang-xml prettyprint-override"><code>&lt;%@page pageEncoding="UTF-8" isErrorPage="true" %&gt;
&lt;%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %&gt;
...
&lt;ul&gt;
 &lt;li&gt;Exception: &lt;c:out value="${requestScope['javax.servlet.error.exception']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Exception type: &lt;c:out value="${requestScope['javax.servlet.error.exception_type']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Exception message: &lt;c:out value="${requestScope['javax.servlet.error.message']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Request URI: &lt;c:out value="${requestScope['javax.servlet.error.request_uri']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Servlet name: &lt;c:out value="${requestScope['javax.servlet.error.servlet_name']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Status code: &lt;c:out value="${requestScope['javax.servlet.error.status_code']}" /&gt;&lt;/li&gt;
 &lt;li&gt;Stack trace: &lt;pre&gt;${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}&lt;/pre&gt;&lt;/li&gt;
&lt;/ul&gt;
</code></pre>

blocks|key|514078|text|在error.jsp中添加以下行|type|unstyled|depth|inlineStyleRanges|entityRanges|data|514079|<%25Logger+log+=+Logger.getLogger("error_jsp.class");
Exception+e+=+(Exception)request.getAttribute("javax.servlet.error.exception");
log.debug(request.getAttribute("javax.servlet.error.message"));
e.printStackTrace();
log.debug(e.getStackTrace());%25>|code-block|syntax|javascript|514080|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In the error.jsp add the below lines

<pre><code>&lt;%Logger log = Logger.getLogger("error_jsp.class");
Exception e = (Exception)request.getAttribute("javax.servlet.error.exception");
log.debug(request.getAttribute("javax.servlet.error.message"));
e.printStackTrace();
log.debug(e.getStackTrace());%&gt;
</code></pre>

I have set my error page like this in web.xml:

<pre><code> &lt;error-page&gt;
 &lt;exception-type&gt;java.lang.Exception&lt;/exception-type&gt;
 &lt;location&gt;/errors/error.jsp&lt;/location&gt;
 &lt;/error-page&gt;
</code></pre>

Now I would like to print stack trace of error on JSP (of course in development mode only). How can I print stack trace of error on my JSP page? I don't use any frameworks for this application, so only default servlet APIs are available for my program.

How can I print error stack trace in JSP page?

我在web.xml中设置了如下错误页面： <error-page> <exception-type>java.lang.Exception</exception-type> <location>/errors/error.jsp</location> </error-page>现在，我想在JSP上打印错误的堆栈跟踪...

问如何在JSP页面中打印错误堆栈跟踪？
EN

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问如何在JSP页面中打印错误堆栈跟踪？
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