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source-code-hunter/docs/Mybatis/核心处理层/Mybatis-SqlCommand.md

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# sqlCommand
- Author: [HuiFer](https://github.com/huifer)
- Description: 该文介绍 mybatis sqlCommand类的源码
- 源码阅读工程: [huifer-mybatis](https://github.com/huifer/javaBook-src/tree/old/mybatis-3)
- `org.apache.ibatis.binding.MapperMethod.SqlCommand`
```java
/**
* 核心内容: sql id , Sql 类型
*/
public static class SqlCommand {
/**
* sql id
*/
private final String name;
/**
* sql 类型select|update|delete|insert|...
*/
private final SqlCommandType type;
/**
* 根据传递的参数 设置sql的一些属性 , sql id , type .
*
* @param configuration
* @param mapperInterface
* @param method
*/
public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method method) {
// 方法名
final String methodName = method.getName();
final Class<?> declaringClass = method.getDeclaringClass();
// Statement 实质是sql
MappedStatement ms = resolveMappedStatement(mapperInterface, methodName, declaringClass,
configuration);
if (ms == null) {
if (method.getAnnotation(Flush.class) != null) {
name = null;
type = SqlCommandType.FLUSH;
} else {
throw new BindingException("Invalid bound statement (not found): "
+ mapperInterface.getName() + "." + methodName);
}
} else {
name = ms.getId();
type = ms.getSqlCommandType();
if (type == SqlCommandType.UNKNOWN) {
throw new BindingException("Unknown execution method for: " + name);
}
}
}
public String getName() {
return name;
}
public SqlCommandType getType() {
return type;
}
/**
* @param mapperInterface mapper.class
* @param methodName 方法名
* @param declaringClass 可能是 mapper.class
* @param configuration
* @return
*/
private MappedStatement resolveMappedStatement(Class<?> mapperInterface, String methodName,
Class<?> declaringClass, Configuration configuration) {
// 接口名称+方法名
String statementId = mapperInterface.getName() + "." + methodName;
if (configuration.hasStatement(statementId)) {
// 从 configuration 获取
return configuration.getMappedStatement(statementId);
} else if (mapperInterface.equals(declaringClass)) {
return null;
}
// new 一个新的实例
for (Class<?> superInterface : mapperInterface.getInterfaces()) {
if (declaringClass.isAssignableFrom(superInterface)) {
MappedStatement ms = resolveMappedStatement(superInterface, methodName,
declaringClass, configuration);
if (ms != null) {
return ms;
}
}
}
return null;
}
}
```
![image-20191218191512184](/images/mybatis/image-20191218191512184.png)
![image-20191218191550550](/images/mybatis/image-20191218191550550.png)