如何在Logback模式編碼器中包含文字大括號？

Question

PatternLayoutEncoder接受的模式的語法在“布局文檔”中部分指定，

在PatternLayout中，括號可用於對轉換模式進行分組。 因此，'（'和'）'具有特殊含義，如果要用作文字，則需要轉義。

...

％字符具有特殊含義...為了將其包括為文字，需要使用反斜杠對其進行轉義，例如“％d％p \\％％m％n”。

但是，它沒有提及字符{和} 。 我希望編寫一個模式，該模式將輸出原義的大括號字符。 為此，我嘗試了在我的logback.xml ：

<encoder>
    <pattern>{</pattern>
</encoder>

這會導致在解析配置文件時，Logback失敗，並顯示NullPointerException 。

然后，通過與文字字符% ， (和)的轉義字符進行類比，我嘗試了：

<encoder>
    <pattern>\{</pattern>
</encoder>

這會導致Logback以相同的方式失敗。

推測NullPointerException是Logback中的錯誤。 如何解決該問題並輸出文字大括號字符？

編輯：這是完整的堆棧跟蹤。

17:44:38,953 |-INFO in ch.qos.logback.core.joran.action.NestedComplexPropertyIA - Assuming default type [ch.qos.logback.classic.encoder.PatternLayoutEncoder] for [encoder] property
Failed to instantiate [ch.qos.logback.classic.LoggerContext]
Reported exception:
java.lang.NullPointerException
    at ch.qos.logback.core.subst.Parser.T(Parser.java:77)
    at ch.qos.logback.core.subst.Parser.E(Parser.java:52)
    at ch.qos.logback.core.subst.Parser.C(Parser.java:122)
    at ch.qos.logback.core.subst.Parser.T(Parser.java:83)
    at ch.qos.logback.core.subst.Parser.E(Parser.java:52)
    at ch.qos.logback.core.subst.Parser.parse(Parser.java:48)
    at ch.qos.logback.core.subst.NodeToStringTransformer.tokenizeAndParseString(NodeToStringTransformer.java:55)
    at ch.qos.logback.core.subst.NodeToStringTransformer.substituteVariable(NodeToStringTransformer.java:46)
    at ch.qos.logback.core.util.OptionHelper.substVars(OptionHelper.java:117)
    at ch.qos.logback.core.joran.spi.InterpretationContext.subst(InterpretationContext.java:159)
    at ch.qos.logback.core.joran.action.NestedBasicPropertyIA.body(NestedBasicPropertyIA.java:87)
    at ch.qos.logback.core.joran.spi.Interpreter.callBodyAction(Interpreter.java:295)
    at ch.qos.logback.core.joran.spi.Interpreter.characters(Interpreter.java:175)
    at ch.qos.logback.core.joran.spi.EventPlayer.play(EventPlayer.java:57)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:149)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:135)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:99)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:49)
    at ch.qos.logback.classic.util.ContextInitializer.configureByResource(ContextInitializer.java:75)
    at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:150)
    at org.slf4j.impl.StaticLoggerBinder.init(StaticLoggerBinder.java:85)
    at org.slf4j.impl.StaticLoggerBinder.<clinit>(StaticLoggerBinder.java:55)
    at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129)
    at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108)
    at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302)
    at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276)
    at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:156)
    at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:132)
    at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:657)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:269)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4973)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5467)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:632)
    at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1740)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1487)
    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:97)
    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1328)
    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1420)
    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:848)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
    at sun.rmi.transport.Transport$1.run(Transport.java:177)
    at sun.rmi.transport.Transport$1.run(Transport.java:174)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)

Answer 1

嘗試對“ {”使用HTML Unicode字符

{

Answer 2

您可以嘗試將單引號/雙引號放在“ {”之前。 對我來說，它解決了一個問題，但提出了另一個問題。 我試圖使用PatternLayout生成JSON。 我可以成功生成用引號引起來的JSON。 但是，JSON解析器開始出現異常。 如果您也嘗試生成JSON並且不能使用附加引號，則可以嘗試JsonLayout。 在https://www.baeldung.com/java-log-json-output中提到了解決方案

我試過的配置

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <layout class="ch.qos.logback.classic.PatternLayout">
        <pattern>'{"timestamp":"%d{yyyy-MM-dd'T'HH:mm:ss.SSS'Z'}", "level":"%p", "classname":"%c", "logmsg":"%m'}</pattern>
    </layout>
</appender>

它在日志下面生成

'{"timestamp":"2018-08-21T15:18:49.998Z", "level":"INFO", "classname":"com.myproject.log4jTest.logbackTest", "logmsg":"Hello world."}'