实体类@Entity中打印对象时，java.lang.*Error

程序员文章站 2022-07-15 14:21:12

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1.报错如下（后面省略部分报错，都是重复报错）：

遇见的报错信息如下（后面省略，都是重复的报错）：
```java
java.lang.*Error
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Employee.toString(Employee.java:29)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at cn.itsource.domain.Department.toString(Department.java:37)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:196)
	at cn.itsource.domain.Department_$$_jvstc24_2.toString(Department_$$_jvstc24_2.java)
........

2.问题分析：
从报错*Error很容易看出，是“栈溢出”的问题，但是我本次的具体情况是这样：
2.1 前提条件：有两个@Entity的实体类：Employee 和 Department
（ Employee中关联了Department，Department也关联了Employee。即 JPA中多对一的关系）
而且两个类都重写了toString方法，Employee 的toString中有Department对应的字段，而Department中又重写了toString
2.2 报错之处：当使用打印语句打印查询到的Employee时，发生栈溢出。
2.3 原因分析：Employee和Department都关联了对方的属性，Employee 重写的toString中有Department对应的字段，Department重写的toString中又有Employee对应的字段。这样打印一方的对象的时候，就会调用一方的toString，由于里面有对方的对象，就会继续去调用对方对象的toString，对方对象的toString里面又有本方对象，又反过来调用本方toString…自己调用自己，没有出口，最终栈溢出。

Employee实体类的配置关系及toString方法：
实体类@Entity中打印对象时，java.lang.*Error

Department的关系配置及toString方法：

最终解决方案：
删除掉一方或者双方的 toString中关联对方的字段