空指针异常：java.lang.NullPointerException: Cannot invoke “Object.getClass()“ because “obj“ is null

- 日理万妓 2024-03-17 22:44 71阅读 0赞

**目录**

问题：

问题指向：

解决：

运行正常：

--------------------

## 问题： ##

> java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "obj" is null  
> at java.base/java.lang.reflect.Method.invoke(Method.java:570)  
> at org.myspringframework.core.ClassPathXmlApplicationContext.lambda$new$0(ClassPathXmlApplicationContext.java:172)  
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)  
> at org.myspringframework.core.ClassPathXmlApplicationContext.lambda$new$1(ClassPathXmlApplicationContext.java:83)  
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)  
> at org.myspringframework.core.ClassPathXmlApplicationContext.lambda$new$2(ClassPathXmlApplicationContext.java:69)  
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)  
> at org.myspringframework.core.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:43)  
> at com.dong.myspring.Test.Test.main(Test.java:10)

### 问题指向： ###

![4e7a12879c494e1ab2bfa318f4679725.png][]

#### 解决： ####

该问题是在一个空对象上调用方法而导致的，所以增加一个**非空判断即可**

if (singletonObject.get(ref) != null) {
     setMethod.invoke(singletonObject.get(id), singletonObject.get(ref));
      }

##### 运行正常： #####

![3d4868c80821462b815c36bf8ae57e14.png][]

[4e7a12879c494e1ab2bfa318f4679725.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/63b4b317f85d4fac99200e4c49049d8d.png
[3d4868c80821462b815c36bf8ae57e14.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/27e79f5ec5014a34af1e47f17922c7e6.png