How to write mybatis configuration file

Steps to write mybatis configuration file: 1. Specify the data source; 2. Configure the transaction manager; 3. Configure the type processor and mapper; 4. Use environment elements; 5. Configure aliases; 6. Configuration mapping file. Detailed introduction: 1. Specify the data source. In the "mybatis-config.xml" file, you need to configure the data source. The data source is an interface, which provides a database connection; 2. Configure the transaction manager to ensure the normality of database transactions. For processing, you also need to configure the transaction manager; 3. Configure the type processor and mapper, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

MyBatis is an excellent persistence layer framework that supports customized SQL, stored procedures and advanced mapping. In MyBatis, the configuration file is an important file used to configure database connections and SQL mapping rules. The following will introduce in detail how to write the configuration file of MyBatis.

First, make sure you have created a MyBatis configuration file, usually named mybatis-config.xml, and placed it in the resources directory of the project.

1. Specify the data source

In the mybatis-config.xml file, you need to configure the data source. A data source is an interface that provides a database connection. The following is an example of using HikariCP as a data source:

<configuration>  
  <!-- 指定数据源 -->  
  <dataSource type="com.zaxxer.hikari.HikariDataSource">  
    <!-- JDBC 驱动类名 -->  
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>  
    <!-- 数据库连接 URL -->  
    <property name="url" value="jdbc:mysql://localhost:3306/mydatabase"/>  
    <!-- 数据库用户名 -->  
    <property name="username" value="myuser"/>  
    <!-- 数据库密码 -->  
    <property name="password" value="mypassword"/>  
  </dataSource>  
    
  <!-- 其他配置项 -->  
</configuration>

2. Configuring the transaction manager

In order to ensure the normal processing of database transactions, you also need to configure the transaction manager . You can choose org.springframework.jdbc.datasource.DataSourceTransactionManager provided by Spring as the transaction manager:

<transactionManager type="org.springframework.jdbc.datasource.DataSourceTransactionManager"/>

3. Configure type processor and mapper

You also Type processors and mappers can be configured to customize data conversion and SQL mapping. For example, you can configure org.mybatis.typehandlers.StringTypeHandler to handle string type fields:

<typeHandlers>  
  <typeHandler handler="org.mybatis.typehandlers.StringTypeHandler"/>  
</typeHandlers>

4. Use the environment element

Use the element Different database connection information can be configured for different environments (development, testing, production, etc.). This is very useful for the isolation of development and production environments:

<environments default="development">  
  <environment id="development">  
    <transactionManager type="JDBC"/>  
    <dataSource type="POOLED">  
      <!-- 开发环境的数据库连接信息 -->  
    </dataSource>  
  </environment>  
  <environment id="production">  
    <transactionManager type="JDBC"/>  
    <dataSource type="UNPOOLED">  
      <!-- 生产环境的数据库连接信息 -->  
    </dataSource>  
  </environment>  
</environments>

5. Configure aliases

In order to simplify the code, you can configure aliases for Java classes, so in the mapping file You can use the alias directly instead of the complete class name:

<typeAliases>  
  <typeAlias alias="User" type="com.example.User"/>  
</typeAliases>

6. Configure the mapping file (optional)

If you have multiple mapping files, you can Specify the path of the mapping file in mybatis-config.xml so that MyBatis can automatically load these files. For example:

<mappers>  
  <mapper resource="com/example/mappers/ExampleMapper.xml"/>  
</mappers>

After completing the above configuration, MyBatis will be able to interact with the database based on the configured database connection information. Please make sure that your database driver is added to the project's dependencies and that all necessary configuration items are set correctly.

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