blocks|key|1997190|text|您可以将异常直接传递给记录器，例如|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1997191|try+{
+++...
}+catch+(Exception+e)+{
++++log.error(+"failed!",+e+);
}|code-block|syntax|javascript|1997192|由log4j来渲染堆栈跟踪。|1997193|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|$]]

You pass the exception directly to the logger, e.g.

<pre><code>try {
 ...
} catch (Exception e) {
 log.error( "failed!", e );
}
</code></pre>

It's up to log4j to render the stack trace.

blocks|key|1783788|text|如果您想在不涉及异常的情况下记录堆栈跟踪，只需执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1783789|String+message+=+"";

for(StackTraceElement+stackTraceElement+:+Thread.currentThread().getStackTrace())+{+++++++++++++++++++++++++
++++message+=+message+%2B+System.lineSeparator()+%2B+stackTraceElement.toString();
}+++
log.warn("Something+weird+happened.+I+will+print+the+the+complete+stacktrace+even+if+we+have+no+exception+just+to+help+you+find+the+cause"+%2B+message);|code-block|syntax|javascript|1783790|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|$]]

If you want to log a stacktrace without involving an exception just do this: 

<pre><code>String message = "";

for(StackTraceElement stackTraceElement : Thread.currentThread().getStackTrace()) { 
 message = message + System.lineSeparator() + stackTraceElement.toString();
} 
log.warn("Something weird happened. I will print the the complete stacktrace even if we have no exception just to help you find the cause" + message);
</code></pre>

blocks|key|1997205|text|您还可以通过ExceptionUtils.getStackTrace以字符串形式获取堆栈跟踪。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1997206|请参阅：ExceptionUtils.java|1997207|为了保持log.error的简单性，我只将它用于log.debug。|1997208|entityMap|0|LINK|mutability|MUTABLE|url|https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/exception/ExceptionUtils.html^0|6|S|0|4|J|0|0|4|9|O|9|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@]|D|@$9|V|A|W|1|X]]|E|$]]|$1|H|3|I|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

You can also get stack trace as string via <code>ExceptionUtils.getStackTrace</code>.

See: <a href="https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/exception/ExceptionUtils.html" rel="noreferrer">ExceptionUtils.java</a>

I use it only for <code>log.debug</code>, to keep <code>log.error</code> simple.

blocks|key|1783727|text|只是因为这件事发生在我身上，而且可能会很有用。如果你这样做|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1783728|try+{
+++...
}+catch+(Exception+e)+{
++++log.error(+"failed!+{}",+e+);
}|code-block|syntax|javascript|1783729|您将获得异常的头部，而不是整个堆栈跟踪。因为记录器会认为您正在传递字符串。没有{}，就像skaffman说的那样|offset|length|style|CODE|1783730|entityMap^0|0|0|13|2|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Just because it happened to me and can be useful.
If you do this

<pre><code>try {
 ...
} catch (Exception e) {
 log.error( "failed! {}", e );
}
</code></pre>

you will get the header of the exception and not the whole stacktrace. Because the logger will think that you are passing a String.
Do it without <code>{}</code> as skaffman said

blocks|key|1997762|text|在Log4j+2中，可以使用Logger.catching()记录捕获的异常的堆栈跟踪。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1997763|++++try+{
++++++++String+msg+=+messages[messages.length];
++++++++logger.error("An+exception+should+have+been+thrown");
++++}+catch+(Exception+ex)+{
++++++++logger.catching(ex);
++++}|code-block|syntax|javascript|1997764|entityMap|0|LINK|mutability|MUTABLE|url|https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/Logger.html#catching-java.lang.Throwable-^0|E|H|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

In Log4j 2, you can use <a href="https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/Logger.html#catching-java.lang.Throwable-" rel="nofollow noreferrer">Logger.catching()</a> to log a stacktrace from an exception that was caught.

<pre><code> try {
 String msg = messages[messages.length];
 logger.error("An exception should have been thrown");
 } catch (Exception ex) {
 logger.catching(ex);
 }
</code></pre>

blocks|key|1997314|text|此答案可能与所提出的问题无关，但与问题的标题有关。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1997315|public+class+ThrowableTest+{

++++public+static+void+main(String[]+args)+{

++++++++Throwable+createdBy+=+new+Throwable("Created+at+main()");
++++++++ByteArrayOutputStream+os+=+new+ByteArrayOutputStream();
++++++++PrintWriter+pw+=+new+PrintWriter(os);
++++++++createdBy.printStackTrace(pw);
++++++++try+{
++++++++++++pw.close();
++++++++++++os.close();
++++++++}+catch+(IOException+e)+{
++++++++++++e.printStackTrace();
++++++++}
++++++++logger.debug(os.toString());
++++}
}|code-block|syntax|javascript|1997316|或|1997317|public+static+String+getStackTrace+(Throwable+t)
{
++++StringWriter+stringWriter+=+new+StringWriter();
++++PrintWriter++printWriter++=+new+PrintWriter(stringWriter);
++++t.printStackTrace(printWriter);
++++printWriter.close();++++//surprise+no+IO+exception+here
++++try+{
++++++++stringWriter.close();
++++}
++++catch+(IOException+e)+{
++++}
++++return+stringWriter.toString();
}|1997318|1997319|StackTraceElement[]+stackTraceElements+=+Thread.currentThread().getStackTrace();
for(StackTraceElement+stackTrace:+stackTraceElements){
++++logger.debug(stackTrace.getClassName()%2B+"++"%2B+stackTrace.getMethodName()%2B"+"%2BstackTrace.getLineNumber());
}|1997320|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Q|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|R|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|K|3|H|5|6|7|T|8|@]|9|@]|A|$]]|$1|L|3|M|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|N|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|O|$]]

This answer may be not related to the question asked but related to title of the question. 

<pre><code>public class ThrowableTest {

 public static void main(String[] args) {

 Throwable createdBy = new Throwable("Created at main()");
 ByteArrayOutputStream os = new ByteArrayOutputStream();
 PrintWriter pw = new PrintWriter(os);
 createdBy.printStackTrace(pw);
 try {
 pw.close();
 os.close();
 } catch (IOException e) {
 e.printStackTrace();
 }
 logger.debug(os.toString());
 }
}
</code></pre>

OR

<pre><code>public static String getStackTrace (Throwable t)
{
 StringWriter stringWriter = new StringWriter();
 PrintWriter printWriter = new PrintWriter(stringWriter);
 t.printStackTrace(printWriter);
 printWriter.close(); //surprise no IO exception here
 try {
 stringWriter.close();
 }
 catch (IOException e) {
 }
 return stringWriter.toString();
}
</code></pre>

OR

<pre><code>StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();
for(StackTraceElement stackTrace: stackTraceElements){
 logger.debug(stackTrace.getClassName()+ " "+ stackTrace.getMethodName()+" "+stackTrace.getLineNumber());
}
</code></pre>

blocks|key|1783941|text|这将是一个很好的log4j错误/异常日志记录--可由splunk/其他日志记录/监控s/w读取。log4j将从异常obj+e获取堆栈跟踪|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1783942|++++try+{
++++++++++---
++++++++++---
++++}+catch+(Exception+e)+{
++++++++log.error("api_name={}+method={}+_message=\"error+description.\"+msg={}",+
++++++++++++++++++new+Object[]{"api_name",+"method_name",+e.getMessage(),+e});
++++}|code-block|syntax|javascript|1783943|entityMap^0|1P|1|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

this would be good log4j error/exception logging - readable by splunk/other logging/monitoring s/w. everything is form of key-value pair.
log4j would get the stack trace from Exception obj <code>e</code>

<pre><code> try {
 ---
 ---
 } catch (Exception e) {
 log.error("api_name={} method={} _message=\"error description.\" msg={}", 
 new Object[]{"api_name", "method_name", e.getMessage(), e});
 }
</code></pre>

blocks|key|1783957|text|Try+this:

catch+(Throwable+t)+{
++++logger.error("any+message"+%2B+t);
++++StackTraceElement[]+s+=+t.getStackTrace();
++++for(StackTraceElement+e+:+s){
++++++++logger.error("\tat+"+%2B+e);
++++}+++
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1783958|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>Try this:

catch (Throwable t) {
 logger.error("any message" + t);
 StackTraceElement[] s = t.getStackTrace();
 for(StackTraceElement e : s){
 logger.error("\tat " + e);
 } 
}
</code></pre>

blocks|key|1997726|text|你可以使用下面的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1997727|import+org.apache.logging.log4j.Logger;
import+org.apache.logging.log4j.LogManager;

public+class+LogWriterUtility+{
++++Logger+log;

++++public+LogWriterUtility(Class<?>+clazz)+{
++++++++log+=+LogManager.getLogger(clazz);
++++}

public+void+errorWithAnalysis(+Exception+exception)+{

++++++++String+message="No+Message+on+error";
++++++++StackTraceElement[]+stackTrace+=+exception.getStackTrace();
++++++++if(stackTrace!=null+&&+stackTrace.length>0)+{
++++++++++++message="";
++++++++++++for+(StackTraceElement+e+:+stackTrace)+{
++++++++++++++++message+%2B=+"\n"+%2B+e.toString();
++++++++++++}
++++++++}
++++++++log.error(message);


++++}

}|code-block|syntax|javascript|1997728|在这里您只需调用：LogWriterUtility.errorWithAnalysis(+YOUR_EXCEPTION_INSTANCE);|offset|length|style|CODE|1997729|它会将stackTrace打印到您的日志中。|1997730|entityMap^0|0|0|9|1P|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You can use bellow code:

<pre><code>import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

public class LogWriterUtility {
 Logger log;

 public LogWriterUtility(Class&lt;?&gt; clazz) {
 log = LogManager.getLogger(clazz);
 }

public void errorWithAnalysis( Exception exception) {

 String message="No Message on error";
 StackTraceElement[] stackTrace = exception.getStackTrace();
 if(stackTrace!=null &amp;&amp; stackTrace.length&gt;0) {
 message="";
 for (StackTraceElement e : stackTrace) {
 message += "\n" + e.toString();
 }
 }
 log.error(message);


 }

}
</code></pre>

Here you can just call : <code>LogWriterUtility.errorWithAnalysis( YOUR_EXCEPTION_INSTANCE);</code>

It will print stackTrace into your log.

blocks|key|1997230|text|创建此class：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1997231|public+class+StdOutErrLog+{

private+static+final+Logger+logger+=+Logger.getLogger(StdOutErrLog.class);

public+static+void+tieSystemOutAndErrToLog()+{
++++System.setOut(createLoggingProxy(System.out));
++++System.setErr(createLoggingProxy(System.err));
}

public+static+PrintStream+createLoggingProxy(final+PrintStream+realPrintStream)+{
++++return+new+PrintStream(realPrintStream)+{
++++++++public+void+print(final+String+string)+{
++++++++++++logger.info(string);
++++++++}
++++++++public+void+println(final+String+string)+{
++++++++++++logger.info(string);
++++++++}
++++};
}
}|code-block|syntax|javascript|1997232|在你的代码中调用这个|1997233|StdOutErrLog.tieSystemOutAndErrToLog();|1997234|entityMap^0|3|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Create this <code>class</code>: 

<pre><code>public class StdOutErrLog {

private static final Logger logger = Logger.getLogger(StdOutErrLog.class);

public static void tieSystemOutAndErrToLog() {
 System.setOut(createLoggingProxy(System.out));
 System.setErr(createLoggingProxy(System.err));
}

public static PrintStream createLoggingProxy(final PrintStream realPrintStream) {
 return new PrintStream(realPrintStream) {
 public void print(final String string) {
 logger.info(string);
 }
 public void println(final String string) {
 logger.info(string);
 }
 };
}
}
</code></pre>

Call this in your code

<pre><code>StdOutErrLog.tieSystemOutAndErrToLog();
</code></pre>

Say you catch an exception and get the following on the standard output (like, say, the console) if you do a e.printStackTrace() :

<pre><code>java.io.FileNotFoundException: so.txt
 at java.io.FileInputStream.&lt;init&gt;(FileInputStream.java)
 at ExTest.readMyFile(ExTest.java:19)
 at ExTest.main(ExTest.java:7)
</code></pre>

Now I want to send this instead to a logger like, say, log4j to get the following:

<pre><code>31947 [AWT-EventQueue-0] ERROR Java.io.FileNotFoundException: so.txt
32204 [AWT-EventQueue-0] ERROR at java.io.FileInputStream.&lt;init&gt;(FileInputStream.java)
32235 [AWT-EventQueue-0] ERROR at ExTest.readMyFile(ExTest.java:19)
32370 [AWT-EventQueue-0] ERROR at ExTest.main(ExTest.java:7)
</code></pre>

How can I do this?

<pre><code>try {
 ...
} catch (Exception e) {
 final String s;
 ... // &lt;-- What goes here?
 log.error( s );
}
</code></pre>

How to send a stacktrace to log4j?

Java

假设您捕获了一个异常，并且如果您执行e.printStackTrace()，则在标准输出(例如控制台)上获得以下内容：java.io.FileNotFoundException: so.txt at java.io.FileInputStream.<init>(FileInputStream.java) at ExTest.readMyFile(ExTest.java:

问如何向log4j发送堆栈跟踪？
EN

回答 10

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