What is the usage of parametertype in MyBatis?

In MyBatis, the parameterType is an optional property used to specify the input parameter type for SQL statements. It can be used for method parameters in the Mapper interface or in SQL statements in XML mapping files.

1. Using the parameterType attribute in the Mapper interface:
2. Retrieve the user with a specific ID from the database.
3. In this example, the parameterType property specifies that the parameter type of the getUserById method is Long, meaning the type of the id parameter in the SQL statement is Long.
4. Use the parameterType attribute in the XML mapping file.
5. Retrieve a user’s information from the database based on their ID.
6. In this example, the parameterType attribute specifies that the type of the id parameter in the SQL statement is Long.

The parameterType attribute can be a Java primitive data type, wrapper class, string, enum class, etc. For complex objects, you can specify the parameter type using the fully qualified class name or an alias.

Specifying the parameterType attribute can more clearly define the input parameter types of an SQL statement, thus enhancing the readability and maintainability of the code.