异常log如下：
java.lang.NullPointerException
at com.trf.service.user.UserServiceImpl.test(UserServiceImpl.java:45)
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:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.runners.ParentRunner 3. e v a l u a t e ( P a r e n t R u n n e r . j a v a : 306 ) a t o r g . j u n i t . r u n n e r s . P a r e n t R u n n e r . r u n ( P a r e n t R u n n e r . j a v a : 413 ) a t o r g . j u n i t . r u n n e r . J U n i t C o r e . r u n ( J U n i t C o r e . j a v a : 137 ) a t c o m . i n t e l l i j . j u n i t 4. J U n i t 4 I d e a T e s t R u n n e r . s t a r t R u n n e r W i t h A r g s ( J U n i t 4 I d e a T e s t R u n n e r . j a v a : 69 ) a t c o m . i n t e l l i j . r t . j u n i t . I d e a T e s t R u n n e r 3.evaluate(ParentRunner.java:306) at org.junit.runners.ParentRunner.run(ParentRunner.java:413) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner 3.evaluate(ParentRunner.java:306)atorg.junit.runners.ParentRunner.run(ParentRunner.java:413)atorg.junit.runner.JUnitCore.run(JUnitCore.java:137)atcom.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)atcom.intellij.rt.junit.IdeaTestRunnerRepeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Process finished with exit code -1
空指针异常很常见，一般是因为数据对象写错导致，而我所遇见的异常是因为数据库中的数据与我在业务层所写的数据不一样，而我写的数据恰巧在数据库中无法找到，进而log报空指针异常
此时有两种方法可以解决
1、在数据库中将数据改为业务层中所编写的代码，但是不建议使用，数据库最好不要随意更改，代价极大
2、在业务层中将数据修改为数据库中对应的数据对象，这个是推荐使用的。