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.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the ERROR level. </p>
*
* @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]