本篇文章为你整理了SLF4J Error Codes（）的详细内容，包含有 SLF4J Error Codes，希望能帮助你了解 SLF4J Error Codes。
This warning, i.e. not an error, message is reported when
no SLF4J providers could be found on the class path. Placing one
(and only one) of slf4j-nop.jar
slf4j-simple.jar, slf4j-reload4j.jar,
slf4j-jdk14.jar or logback-classic.jar on the
class path should solve the problem. Note that these providers
must target slf4j-api 2.0.x or later.
In the absence of a provider, SLF4J will default to a
no-operation (NOP) logger provider.
Please note that slf4j-api version 2.0.x and later use
the ServiceLoader
mechanism. Earlier versions relied on the static
binder mechanism which is no longer honored by slf4j-api.
Please read the FAQ
entry What has changed in SLF4J version 2.0.0? for further important details.
If you are responsible for packaging an application and do not
care about logging, then placing slf4j-nop.jar on the
class path of your application will get rid of this warning
message. Note that embedded components such as libraries or
frameworks should not declare a dependency on any SLF4J providers
but only depend on slf4j-api. When a library declares a
compile-time dependency on a SLF4J provider, it imposes that
provider on the end-user, thus negating SLF4Js purpose.
Planning for the advent of Jigsaw (Java 9), slf4j-api version
2.0.x and later use the ServiceLoader
mechanism. Earlier versions of SLF4J relied on
the static binder mechanism which is no longer honored by
slf4j-api version 2.0.x.
In case SLF4J finds no providers targeting SLF4J 2.0.x but finds
instead bindings targeting SLF4J 1.7 or earlier, it will list the
bindings it finds but otherwise will ignore them.
This can be solved by placing an SLF4J provider on your
classpath, such providers include logback version 1.3.x and
later, as well as one of slf4j-reload4j, slf4j-jdk14, slf4j-simple
version 2.0.0 or later.
See also the FAQ
entry What has changed in SLF4J version 2.0.0? for further important details.
This IllegalStateException is thrown
post-initialization and informs the user that initialization of
LoggerFactory has failed.
Note It is important to
realize that the exception causing the failure was thrown at an
earlier stage. This earlier exception should provide more
valuable information about the root cause of the problem.
Given the structure of the commons-logging API, in particular
as implemented by SLF4J, the
o.a.commons.logging.impl.SLF4FLogFactory#release()
method should never be called. However, depending on the
deployment of commons-logging.jar files in your servlet
container, release() method may be unexpectedly
invoked by a copy of
org.apache.commons.logging.LogFactory class shipping
with commons-logging.jar.
This is a relatively common occurrence with recent versions of
Tomcat, especially if you place jcl-over-slf4j.jar in
WEB-INF/lib directory of your web-application instead of
$TOMCAT_HOME/common/lib, where $TOMCAT_HOME stands for
the directory where Tomcat is installed. In order to fully benefit
from the stability offered by jcl-over-slf4j.jar, we
recommend that you place jcl-over-slf4j.jar in
$TOMCAT_HOME/common/lib without placing a copy in your
web-applications.
Please also see bug #22.
An UnsupportedOperationException is thrown whenever
one of the protected methods introduced in JCL 1.1 are
invoked. These methods are invoked by LogFactory
implementations shipping with
commons-logging.jar. However, the LogFactory
implemented by jcl-over-slf4j.jar, namely
SLF4FLogFactory, does not call any of these methods.
If you observe this problem, then it is highly probable that you
have a copy of commons-logging.jar in your class path
overriding the classes shipping with
jcl-over-slf4j.jar. Note that this issue is very similar
in nature to the warning issued when the
"o.a.commons.logging.impl.SLF4FLogFactory.release()" method is
invoked, discussed in the previous item.
Logger name mismatch warnings are printed only if the
slf4j.detectLoggerNameMismatch system property is set
to true. By default, this property is not set and no warnings will
be printed even in case of a logger name mismatch.
since 1.7.9 The warning will
be printed in case the name of the logger specified via a class
passed as an argument to the
LoggerFactory.getLogger(Class) method differs from
the name of the caller as computed internally by SLF4J.
For example, the following code snippet
package com.acme;
import com.foo.Kangaroo;
class Fruit {
Logger logger = LoggerFactory.getLogger(Kangaroo.class);
}
will result in the warning
SLF4J: Detected logger name mismatch. Given name: "com.foo.Kangaroo"; computed name: "com.acme.Fruit".
but only if slf4j.detectLoggerNameMismatch system
property is set to true.
No warning will be issued for the special case where the class
in which the logger is defined is a super-type of the class
parameter passed as argument. For example,
class A {
Logger logger = LoggerFactory.getLogger(getClass());
class B extends A {
// no mismatch warning will be issued when B is instantiated
// given that class A is a super-type of class B
}
If you come across a mismatch warning which cannot be
explained, then you might have spotted a white elephant, that is a
very rare occurrence where SLF4J cannot correctly compute the name
of the class where a logger is defined. We are very interested to
learn about such cases. If and when you spot an inexplicable
mismatch, please do file a bug report with us.
This warning message is reported when the
org.slf4j.impl.StaticLoggerBinder class could not be
loaded into memory. This happens when no appropriate SLF4J
binding could be found on the class path. Placing one (and only
one) of slf4j-nop.jar slf4j-simple.jar,
slf4j-log4j12.jar, slf4j-jdk14.jar or
logback-classic.jar on the class path should solve the
problem.
Note that slf4j-api versions 2.0.x and later use the ServiceLoader
mechanism. Backends such as logback 1.3 and later which target
slf4j-api 2.x, do not ship with
org.slf4j.impl.StaticLoggerBinder. If you place a
logging backend which targets slf4j-api 2.0.x, you need
slf4j-api-2.x.jar on the classpath. See also relevant faq entry.
since 1.6.0 As of SLF4J version 1.6,
in the absence of a binding, SLF4J will default to a no-operation
(NOP) logger implementation.
If you are responsible for packaging an application and do not
care about logging, then placing slf4j-nop.jar on the
class path of your application will get rid of this warning
message. Note that embedded components such as libraries or
frameworks should not declare a dependency on any SLF4J binding
but only depend on slf4j-api. When a library declares a
compile-time dependency on a SLF4J binding, it imposes that
binding on the end-user, thus negating SLF4Js purpose.
SLF4J API is designed to bind with one and only one underlying
logging framework at a time. If more than one binding is present
on the class path, SLF4J will emit a warning, listing the location
of those bindings.
When multiple bindings are available on the class path, select
one and only one binding you wish to use, and remove the other
bindings. For example, if you have both
slf4j-simple-2.0.6.jar and
slf4j-nop-2.0.6.jar on the class path and you wish
to use the nop (no-operation) binding, then remove
slf4j-simple-2.0.6.jar from the class path.
The list of locations that SLF4J provides in this warning
usually provides sufficient information to identify the dependency
transitively pulling in an unwanted SLF4J binding into your
project. In your projects pom.xml file, exclude this SLF4J
binding when declaring the unscrupulous dependency. For example,
cassandra-all version 0.8.1 declares both log4j
and slf4j-log4j12 as compile-time dependencies. Thus,
when you include cassandra-all as a dependency in your
project, the cassandra-all declaration will cause both
slf4j-log4j12.jar and log4j.jar to be pulled in
as dependencies. In case you do not wish to use log4j as the
SLF4J backend, you can instruct Maven to exclude these two
artifacts as shown next:
dependencies>
dependency>
groupId> org.apache.cassandra /groupId>
artifactId>cassandra-all /artifactId>
version>0.8.1 /version>
exclusions>
exclusion>
groupId>org.slf4j /groupId>
artifactId>slf4j-log4j12 /artifactId>
/exclusion>
exclusion>
groupId>log4j /groupId>
artifactId>log4j /artifactId>
/exclusion>
/exclusions>
/dependency>
/dependencies>
Note The warning emitted by
SLF4J is just that, a warning. Even when multiple bindings are
present, SLF4J will pick one logging framework/implementation and
bind with it. The way SLF4J picks a binding is determined by the
JVM and for all practical purposes should be considered random. As
of version 1.6.6, SLF4J will name the framework/implementation
class it is actually bound to.
Embedded components such as libraries or frameworks should not
declare a dependency on any SLF4J binding but only depend on
slf4j-api. When a library declares a compile-time dependency on a
SLF4J binding, it imposes that binding on the end-user, thus
negating SLF4J s purpose. When you come across an embedded
component declaring a compile-time dependency on any SLF4J binding,
please take the time to contact the authors of said
component/library and kindly ask them to mend their ways.
An SLF4J binding designates an artifact such as
slf4j-jdk14.jar or slf4j-log4j12.jar used to
bind slf4j to an underlying logging framework, say,
java.util.logging and respectively log4j.
Mixing different versions of slf4j-api.jar and SLF4J
binding (a.k.a. provider since 2.0.0) can cause problems. For
example, if you are using slf4j-api-2.0.6.jar, then
you should also use slf4j-simple-2.0.6.jar, using
slf4j-simple-1.5.5.jar will not work.
Note From the client s
perspective all versions of slf4j-api are compatible. Client code
compiled with slf4j-api-N.jar will run perfectly fine
with slf4j-api-M.jar for any N and M. You only need to
ensure that the version of your binding matches that of the
slf4j-api.jar. You do not have to worry about the version of
slf4j-api.jar used by a given dependency in your project. You can
always use any version of slf4j-api.jar, and as long as
the version of slf4j-api.jar and its binding match, you
should be fine.
At initialization time, if SLF4J suspects that there may be an
api vs. binding version mismatch problem, it will emit a warning
about the suspected mismatch.
This error is reported when the LoggerFactory
class could not find an appropriate binding. Placing one (and only
one) of slf4j-nop.jar, slf4j-simple.jar,
slf4j-log4j12.jar, slf4j-jdk14.jar or
logback-classic.jar on the class path should prove to be
an effective remedy.
log4j-over-slf4j.jar AND slf4j-reload4j on the class path,
preempting StackOverflowError.
The purpose of slf4j-reload4j module is to delegate or redirect
calls made to an SLF4J logger to log4j/reload4j. The purpose of
the log4j-over-slf4j module is to redirect calls made to a log4j
logger to SLF4J. If SLF4J is bound withslf4j-reload4j.jar
and log4j-over-slf4j.jar is also present on the class
path, a StackOverflowError will inevitably occur
immediately after the first invocation of an SLF4J or a log4j
logger.
Here is how the exception might look like:
Exception in thread "main" java.lang.StackOverflowError
at java.util.Hashtable.containsKey(Hashtable.java:306)
at org.apache.log4j.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:36)
at org.apache.log4j.LogManager.getLogger(LogManager.java:39)
at org.slf4j.impl.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:73)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:249)
at org.apache.log4j.Category. init>(Category.java:53)
at org.apache.log4j.Logger.. init>(Logger.java:35)
at org.apache.log4j.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:39)
at org.apache.log4j.LogManager.getLogger(LogManager.java:39)
at org.slf4j.impl.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:73)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:249)
at org.apache.log4j.Category.. init>(Category.java:53)
at org.apache.log4j.Logger.. init>(Logger.java:35)
at org.apache.log4j.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:39)
at org.apache.log4j.LogManager.getLogger(LogManager.java:39)
subsequent lines omitted...
Since 1.5.11 SLF4J software preempts
the inevitable stack overflow error by throwing an exception with
details about the actual cause of the problem. This is deemed to
be better than leaving the user wondering about the reasons of the
StackOverflowError.
Note that since reload4j provides the log4j 1.x API,
reload4j.jar and log4j-over-slf4j.jar cannot be present
simultaneously on your classpath.
For more background on this topic see Bridging legacy APIs.
jcl-over-slf4j.jar AND slf4j-jcl.jar on the class path, preempting
StackOverflowError.
The purpose of slf4j-jcl module is to delegate or redirect
calls made to an SLF4J logger to jakarta commons logging
(JCL). The purpose of the jcl-over-slf4j module is to redirect
calls made to a JCL logger to SLF4J. If SLF4J is bound with
slf4j-jcl.jar and jcl-over-slf4j.jar is also
present on the class path, then a StackOverflowError
will inevitably occur immediately after the first invocation of an
SLF4J or a JCL logger.
Here is how the exception might look like:
Exception in thread "main" java.lang.StackOverflowError
at java.lang.String.hashCode(String.java:1482)
at java.util.HashMap.get(HashMap.java:300)
at org.slf4j.impl.JCLLoggerFactory.getLogger(JCLLoggerFactory.java:67)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:249)
at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:155)
at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:289)
at org.slf4j.impl.JCLLoggerFactory.getLogger(JCLLoggerFactory.java:69)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:249)
at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:155)
subsequent lines omitted...
Since 1.5.11 SLF4J software preempts
the inevitable stack overflow error by throwing an exception with
details about the actual cause of the problem. This is deemed to
be better than leaving the user wondering about the reasons of the
StackOverflowError.
For more background on this topic see Bridging legacy APIs.
Exception in thread "main" java.lang.NoSuchFieldError: tlm
at org.apache.log4j.MDCFriend.fixForJava9(MDCFriend.java:11)
at org.slf4j.impl.Log4jMDCAdapter.(Log4jMDCAdapter.java:38)
at Main.main(Main.java:5)
The NoSuchFieldError is thrown
when slf4j-log4j12 attempts to access the tlm package
private field in org.apache.log4j.MDC which was
specified as being of type
java.lang.Object in log4j 1.2.x but was changed
to java.lang.ThreadLocal in reload4j. Moreover, such
access to package private fields from different modules is not
authorized by default in modularized applications in Java 9 and
later.
To keep a long story short, the NoSuchFieldError
can be avoided by using slf4j-reload4j.jar
with reload4j.jar. Stated
differently, org.slf4j.MDC cannot be used with
the slf4j-log4j12.jar and reload4j.jar
combination.
Update: The issue described
above was fixed in reload4j 1.2.21. Although it is still
recommended that you use slf4j-reload4j as the preferred adapter
for the slf4j/reload4j combination, with reload4j version 1.2.21
and later you can freely mix any version of slf4j-log4j12, if you
need to.
This error indicates that appropriate SLF4J binding could not
be found on the class path. Placing one (and only one) of
slf4j-nop.jar, slf4j-simple.jar,
slf4j-log4j12.jar, slf4j-jdk14.jar or
logback-classic.jar on the class path should solve the
problem.
This error is reported when org.slf4j.MDC class
has not been initialized correctly. Same cause and remedy as the
previously listed item.
A number (N) of logging calls
during the initialization phase have been intercepted and are now
being replayed. These are subject to the filtering rules of the
underlying logging system.
since 1.7.15 Logging calls made
during the initialization phase are recorded and replayed
post-initialization. Note that the replayed logging calls are
subject to filtering by the underlying logging system.
In principle, replaying only occurs for applications which are
already multithreaded at the time the first logging call occurs.
See also substitute loggers.
Highly configurable
logging systems such as logback and log4j may create components
which invoke loggers during their own initialization. See issue
LOGBACK-127
for a typical occurrence. However, since the binding process with
SLF4J has not yet completed (because the underlying logging system
was not yet completely loaded into memory), it is not possible to
honor such logger creation requests.
To avoid this chicken-and-egg problem, SLF4J creates substitute
loggers during this phase (initialization). Calls made to the
substitute loggers during this phase are simply dropped. After the
initialization completes, the substitute logger will delegate
logging calls to the appropriate logger implementation and
otherwise will function as any other logger returned by
LoggerFactory.
If any substitute logger had to be created, SLF4J will emit a
listing of such loggers. This list is intended to let you know
that any logging calls made to these loggers during initialization
have been dropped.
See also intercepted and replayed logging calls.
The trace level was added to log4j in version 1.2.12 released
on August 29, 2005. The trace level was added to the SLF4J API in
version 1.4.0 on May 16th, 2007. Thus, starting with SLF4J 1.4.0,
the log4j binding for SLF4J requires log4j version 1.2.12 or
above.
However, as reported in issue 59, in some
environments it may be difficult to upgrade the log4j version. To
accommodate such circumstances, SLF4Js
Log4jLoggerAdapter will map the TRACE level as
DEBUG.
Logback-classic version 1.1.4 and later require slf4j-api
version 1.7.15 or later.
With an earlier slf4j-api.jar in the classpath, attempting
introspection of a Logger instance returned by logback version
1.1.4 or later will result in a NoClassDefFoundError
similar to that shown below.
Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/event/LoggingEvent
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2451)
at java.lang.Class.privateGetPublicMethods(Class.java:2571)
at java.lang.Class.getMethods(Class.java:1429)
at java.beans.Introspector.getPublicDeclaredMethods(Introspector.java:1261)
at java.beans.Introspector.getTargetMethodInfo(Introspector.java:1122)
at java.beans.Introspector.getBeanInfo(Introspector.java:414)
at java.beans.Introspector.getBeanInfo(Introspector.java:161)
Placing slf4j-api.jar version 1.7.15 or later in the
classpath should solve the issue.
Note that this problem only occurs with logback version 1.1.4
and later, other bindings such as slf4j-log4j, slf4j-jdk14 and
slf4j-simple are unaffected.
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