MyBatis 源码分析（五）：异常模块

1、前言

上一篇我们解了Mybatis解析器模块，本篇我们来了解反射模块。本文，我们来分享 MyBatis 的异常模块。

对应 exceptions 包，如下图所示：

在 MyBatis源码分析（二）：项目结构中，简单介绍了这个模块：

定义了 MyBatis 专有的 PersistenceException 和 TooManyResultsException 异常。

实际上，MyBatis 不仅仅在 exceptions 包下有异常，在其他包下也有异常，整体如下类图：

2、源码分析

2.1、`exceptions` 包

2.1.1 IbatisException

org.apache.ibatis.exceptions.IbatisException ，实现 RuntimeException 类，IBatis 的异常基类。代码如下：

|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| @Deprecated public class IbatisException extends RuntimeException { private static final long serialVersionUID = 3880206998166270511L; public IbatisException() { super(); } public IbatisException(String message) { super(message); } public IbatisException(String message, Throwable cause) { super(message, cause); } public IbatisException(Throwable cause) { super(cause); } } |

实际上，IbatisException 已经在 2015 年被废弃，取代它的是 PersistenceException 类。

2.1.2、 PersistenceException

org.apache.ibatis.exceptions.PersistenceException ，继承 IbatisException 类，目前 MyBatis 真正的异常基类。代码如下：

|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class PersistenceException extends IbatisException { private static final long serialVersionUID = -7537395265357977271L; public PersistenceException() { super(); } public PersistenceException(String message) { super(message); } public PersistenceException(String message, Throwable cause) { super(message, cause); } public PersistenceException(Throwable cause) { super(cause); } } |

2.1.3 ExceptionFactory

org.apache.ibatis.exceptions.ExceptionFactory ，异常工厂。代码如下：

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class ExceptionFactory { private ExceptionFactory() { // Prevent Instantiation } /** * 包装异常成 PersistenceException * * @param message 消息 * @param e 发生的异常 * @return PersistenceException */ public static RuntimeException wrapException(String message, Exception e) { return new PersistenceException(ErrorContext.instance().message(message).cause(e).toString(), e); } } |

2.1.4、 TooManyResultsException

org.apache.ibatis.exceptions.TooManyResultsException ，继承 PersistenceException 类，查询返回过多结果的异常。期望返回一条，实际返回了多条。代码如下：

|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class TooManyResultsException extends PersistenceException { private static final long serialVersionUID = 8935197089745865786L; public TooManyResultsException() { super(); } public TooManyResultsException(String message) { super(message); } public TooManyResultsException(String message, Throwable cause) { super(message, cause); } public TooManyResultsException(Throwable cause) { super(cause); } } |

2.2、`parsing` 包

2.2.1、 ParsingException

org.apache.ibatis.parsing.ParsingException ，继承 PersistenceException 类，解析异常。代码如下：

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class ParsingException extends PersistenceException { private static final long serialVersionUID = -176685891441325943L; public ParsingException() { super(); } public ParsingException(String message) { super(message); } public ParsingException(String message, Throwable cause) { super(message, cause); } public ParsingException(Throwable cause) { super(cause); } } |