如何用slf4j打印日志既使用占位符又打印异常堆栈信息（仍然使用{}占位符，不拼接，不使用String.format）

背景

之前有过一个疑惑，就是使用slf4j的API去打印错误日志的时候，如果既要打印参数又要打印异常的堆栈信息，则前面的部分只能用字符串拼接的方式，如

log.error("error msg,request param1:" + param1 + "param2:" + param2 + ",param3" + param3, e);

上述方法其实是使用了slf4j的下面的API：

/**
 * Log an exception (throwable) at the ERROR level with an
 * accompanying message.
 *
 * @param msg the message accompanying the exception
 * @param t   the exception (throwable) to log
 */
public void error(String msg, Throwable t);

上述参数一多，拼接容易出错，也很麻烦。或者只能使用变通的方式，比如

log.error(String.format("error msg,request param1:%s,param2:%s,param3:%s", param1, param2, param3), e);

其实使用 String.format 有个不好的地方，就是如果参数对不上直接抛异常而不是像log.xxxx() 那样只是忽略，加个日志不测一下说不定还能捅出大窟窿

其实是有解决方案的

解决方案

其实slf4j的有些api是已经支持了的！直接使用 log.error/info/debug...("your log,param1:{},param2:{},param3:{}", p1, p2, p3, e) 即可，e是异常，作为最后一个参数，即使最终参数的个数比 {} 占位符多，但是实际是可以的（并且IDEA非常智能不会提示参数个数匹配不上的警告）。整个演示如下

使用 @Slf4j 了，然后使用 log 来打印日志

@GetMapping("/testLog1")
public String testLog1(@RequestParam String param1, @RequestParam String param2, @RequestParam String param3) {
    try {
        int i = 8 / 0;
    } catch (Exception e) {
        log.error("error msg,request param1:{},param2:{},param3:{}", param1, param2, param3, e);
    }
    return "testLog1";
}

上述方法其实是使用了slf4j的这个API:

/**
 * Log a message at the ERROR level according to the specified format
 * and arguments.
 * 

 * 
This form avoids superfluous object creation when the logger
 * is disabled for the ERROR level. 
 *
 * @param format the format string
 * @param arg1   the first argument
 * @param arg2   the second argument
 */
public void error(String format, Object arg1, Object arg2);

实际打印出来的错误信息，可以看到堆栈信息完美打印了出来：

2023-06-20 08:50:42.802 ERROR 64278 --- [nio-8080-exec-1] c.e.demo.demos.web.TestLogController     : error msg,request param1:v1,param2:v2,param3:v3

java.lang.ArithmeticException: / by zero
	at com.example.demo.demos.web.TestLogController.testLog1(TestLogController.java:15) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_301]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_301]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_301]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_301]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) [spring-web-5.3.23.jar:5.3.23]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) [spring-web-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1071) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:964) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.23.jar:5.3.23]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.3.23.jar:5.3.23]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:670) [tomcat-embed-core-9.0.68.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.23.jar:5.3.23]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:779) [tomcat-embed-core-9.0.68.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.23.jar:5.3.23]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) [spring-web-5.3.23.jar:5.3.23]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.3.23.jar:5.3.23]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) [spring-web-5.3.23.jar:5.3.23]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.3.23.jar:5.3.23]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) [spring-web-5.3.23.jar:5.3.23]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1789) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.68.jar:9.0.68]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_301]