在单元测试中写入以下方法:
testMain()主方法,
out()里面嵌套了两层try catch
异常代码写在内层try中
@Test
public void testMain(){
out();
log.info("后续处理业务");
}
public void out(){
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0; //异常代码
}catch (Exception e){
log.error("内层异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
}
}
日志信息：
外层输出 20:38:27.172 [main] ERROR com.eshore.paas.ops.serv.secondalert.secondalertTest - 内层异常 java.lang.ArithmeticException: / by zero at com.eshore.paas.ops.serv.secondalert.secondalertTest.out(secondalertTest.java:52) at com.eshore.paas.ops.serv.secondalert.secondalertTest.testMain(secondalertTest.java:42) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.frameworkMethod$1.runReflectiveCall(frameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.frameworkMethod.invokeExplosively(frameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:221) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54) 20:38:27.179 [main] INFO com.eshore.paas.ops.serv.secondalert.secondalertTest - 后续处理业务
可以看到,内层try中的异常由内层catch处理了，外层catch并未处理，主方法后续业务逻辑并未受到影响，可正常执行.
示例二：内层try catch中添加throw new RuntimeException("内层抛出异常",e)将异常抛出
@Test
public void testMain(){
out();
log.info("后续处理业务");
}
public void out(){
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0;
}catch (Exception e){
log.error("内层异常",e);
//向外抛出异常
throw new RuntimeException("抛出异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
}
}
日志信息:
外层输出 20:47:15.890 [main] ERROR com.eshore.paas.ops.serv.secondalert.secondalertTest - 内层异常 java.lang.ArithmeticException: / by zero at com.eshore.paas.ops.serv.secondalert.secondalertTest.out(secondalertTest.java:52) at com.eshore.paas.ops.serv.secondalert.secondalertTest.testMain(secondalertTest.java:42) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.frameworkMethod$1.runReflectiveCall(frameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.frameworkMethod.invokeExplosively(frameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:221) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54) 20:47:15.894 [main] ERROR com.eshore.paas.ops.serv.secondalert.secondalertTest - 外层异常 java.lang.RuntimeException: 内层抛出异常 at com.eshore.paas.ops.serv.secondalert.secondalertTest.out(secondalertTest.java:55) at com.eshore.paas.ops.serv.secondalert.secondalertTest.testMain(secondalertTest.java:42) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.frameworkMethod$1.runReflectiveCall(frameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.frameworkMethod.invokeExplosively(frameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:221) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54) Caused by: java.lang.ArithmeticException: / by zero at com.eshore.paas.ops.serv.secondalert.secondalertTest.out(secondalertTest.java:52) ... 23 common frames omitted 20:47:15.894 [main] INFO com.eshore.paas.ops.serv.secondalert.secondalertTest - 后续处理业务
内层try catch向外抛出异常以后，外层try catch捕获了异常，并打印日志。主方法中后续处理业务逻辑正常执行。
示例三：在外层try catch中再次将异常抛出throw new RuntimeException("外层抛出异常",e);
@Test
public void testMain(){
out();
log.info("后续处理业务");
}
public void out(){
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0;
}catch (Exception e){
log.error("内层异常",e);
throw new RuntimeException("内层抛出异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
//向外抛出异常
throw new RuntimeException("外层抛出异常",e);
}
}
日志信息：
可以看到，程序运行错误。
因为out()方法外层try catch抛出异常以后，主方法并未进行处理导致的
改进:
在主方法中，对out()添加一层try catch进行异常处理:
@Test
public void testMain(){
//添加异常处理
try {
out();
}catch (Exception e){
log.info("处理out()方法异常",e);
}
log.info("后续处理业务");
}
public void out(){
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0;
}catch (Exception e){
log.error("内层异常",e);
throw new RuntimeException("内层抛出异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
throw new RuntimeException("外层抛出异常",e);
}
}
此时可以看到主方法处理异常以后，可以正常向下执行.
如果out()方法中的异常代码不在try 代码块中，且主方法也没有对out()方法进行异常捕获处理会怎样?
代码：
@Test
public void testMain(){
out();
log.info("后续处理业务");
}
public void out(){
//添加异常代码，不在try 代码块中
int j = 3/0;
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0;
}catch (Exception e){
log.error("内层异常",e);
throw new RuntimeException("内层抛出异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
throw new RuntimeException("外层抛出异常",e);
}
}
日志:
程序直接报错
那么该如何处理?
在out()的上层方法即主方法中,对out()进行异常处理
@Test
public void testMain(){
//对out()进行异常处理
try {
out();
}catch (Exception e){
log.info("处理out()方法异常",e);
}
log.info("后续处理业务");
}
public void out(){
int j = 3/0;
//外层try
try {
System.out.println("外层输出");
//内层try
try {
int i = 2/0;
}catch (Exception e){
log.error("内层异常",e);
throw new RuntimeException("内层抛出异常",e);
}
}catch (Exception e){
log.error("外层异常",e);
throw new RuntimeException("外层抛出异常",e);
}
}
日志信息:
可以看出程序正常执行.
结论:
下层方法中的异常代码没有在try 代码块中，只需在上层方法中进行异常处理即可
