What is the purpose of the parameterType in MyBatis?

In MyBatis, the parameterType is used to specify the type of parameter in the mapping statement. Its purpose is to inform MyBatis what type to convert the incoming parameter to when executing the mapping statement, and to be able to retrieve the properties or methods of the parameter by its type.

Specifically, parameterType serves several functions:

1. Data type conversion: MyBatis will automatically convert incoming parameters to the corresponding Java type based on the specified parameterType. For example, if parameterType is specified as String, MyBatis will automatically convert the incoming parameter to a String type.
2. Accessing the properties or methods of parameters: MyBatis can retrieve the properties or methods of a parameter object based on its type. For example, one can access the property values or call methods of a parameter object specified by the parameterType.
3. Parameter Mapping: MyBatis automatically maps parameters based on the type specified in parameterType. For example, if parameterType is specified as a JavaBean type, MyBatis will map parameters automatically based on the property names of the parameter object and the placeholders in the mapping statement.

In general, the purpose of parameterType is to specify the type of parameters in the mapping statement so that MyBatis can correctly handle parameter conversion, access parameter properties or methods, and parameter mapping operations.