Spring注入后反射的空指针异常
自动装配是在spring环境下当使用该类的实例时由spring容器完成了类的实例化过程，包括对依赖对象的实例化过程。
而通过反射创建实例时，是根据你调用的构造函数完成的实例化过程，没有容器的自动化创建实例了，所以需要自己对依赖对象进行注入。
所以依赖spring容器实例化和自己用反射实例化是两种独立的方式，不能相互渗透的。
1. 异常说明
在单元测试类中，要单独测一个类中的private方法，所以想通过反射获得此方法，解除私有限定，然后进行调用。此类为Service其中注入了许多的Mapper，因此在通过调用此私有方法的时候报了空指针异常的错误，错误如下：
java.lang.reflect.InvocationTargetException
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 com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImplTest.testInvoke(CheckAmsPmtAndPtsFlowServiceImplTest.java:78)
at com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImplTest.insertByList(CheckAmsPmtAndPtsFlowServiceImplTest.java:69)
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.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
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$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.NullPointerException
at com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImpl.succesExitReove(CheckAmsPmtAndPtsFlowServiceImpl.java:247)
... 36 more
注意最后面是由NullPointerException引起的。通过Debug进去以后发现是与数据库交互的Mapper没有注入进来。
单元测试代码如下：
@Autowired
private CheckAmsPmtAndPtsFlowServiceImpl checkAmsPmtAndPtsFlowServiceI;
@Test
public void insertByList()
throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException,
NoSuchFieldException {
List<TBapCheckResultSave> list = new ArrayList<>();
Class cls = Class.forName("service.impl.CheckAmsPmtAndPtsFlowServiceImpl");
Class[] cArg = new Class[5];
cArg[0] = List.class;
cArg[1] = boolean.class;
cArg[2] = String.class;
cArg[3] = String.class;
cArg[4] = String.class;
Method succesExitReove = cls.getDeclaredMethod("succesExitReove",cArg);
succesExitReove.setAccessible(true);
succesExitReove.invoke(checkAmsPmtAndPtsFlowServiceI,list,true,"1","1","2");
}
此处有个知识点：在调用
getDeclaredMethod()获得指定的方法时，第二个参数是方法的传参类型，包装类和其基本类型是不一样，例如下面方法为boolean，如果此时在上面cArg[1] = Boolean.class;写为其包装类型的话，那么就会报错找不到此方法的错误
被反射的类中方法succesExitReove ()如下
@Autowired
private TMemAcPmtDtlPoMapper tMemAcPmtDtlPoMapper;
private void succesExitReove(List<TBapCheckResultSave> result, boolean isFen, String sourceType, String opId, String batchId) {
Iterator<TBapCheckResultSave> iteDownPtsNoCodeSuccces = result.iterator();
while (iteDownPtsNoCodeSuccces.hasNext()) {
int count;
if (isFen) {
count = tMemAcPmtDtlPoMapper.queryCheckFlow(bapCheckResult.getOutTransId());
} else {
count = tMemAcPmtDtlPoMapper.queryCheckFlow(bapCheckResult.getTransId());
}
bapCheckResult.setPmtCount(count);
if (count > 0) {
iteDownPtsNoCodeSuccces.remove();
}
}
}
此处在Debug时发现tMemAcPmtDtlPoMapper为空。
2. 解决办法
在单元测试类中
@Autowired要用的Mapper，然后通过反射获得上面方法要用到Mapper的变量，为其赋值即可
单元测试代码如下
@Autowired
private CheckAmsPmtAndPtsFlowServiceImpl checkAmsPmtAndPtsFlowServiceI;
--在单元测试类中进行依赖注入Mapper
@Autowired
private TMemAcPmtDtlPoMapper tMemAcPmtDtlPoMapper;
@Test
public void insertByList()
throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException,
NoSuchFieldException {
List<TBapCheckResultSave> list = new ArrayList<>();
Class cls = Class.forName("service.impl.CheckAmsPmtAndPtsFlowServiceImpl");
Class[] cArg = new Class[5];
cArg[0] = List.class;
cArg[1] = boolean.class;
cArg[2] = String.class;
cArg[3] = String.class;
cArg[4] = String.class;
Field a1 = cls.getDeclaredField("tMemAcPmtDtlPoMapper");
Method succesExitReove = cls.getDeclaredMethod("succesExitReove",cArg);
succesExitReove.setAccessible(true);
--在此为反射的类进行赋值Mapper
Field a1 = cls.getDeclaredField("tMemAcPmtDtlPoMapper");
a1.setAccessible(true);
a1.set(checkAmsPmtAndPtsFlowServiceI,tMemAcPmtDtlPoMapper);
succesExitReove.invoke(checkAmsPmtAndPtsFlowServiceI,list,true,"1","1","2");
}
