mybatis-java-enterprise-usage-guide.md

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The Overview of MyBatis Java Enterprise Usage Guide

Here's a step-by-step guide to using MyBatis in a Java Enterprise application:

1. Add the MyBatis dependency to your project: You can add the MyBatis dependency to your project by downloading the JAR files from the MyBatis website or using a build tool like Maven or Gradle. Here's an example of how to add the MyBatis dependency using Maven:

   <dependency>
       <groupId>org.mybatis</groupId>
       <artifactId>mybatis</artifactId>
       <version>3.5.7</version>
   </dependency>

2. Configure MyBatis: MyBatis uses an XML-based configuration file to define how SQL statements are mapped to Java objects. Here's an example of how to configure MyBatis:

   <configuration>
       <environments default="development">
           <environment id="development">
               <transactionManager type="JDBC"/>
               <dataSource type="POOLED">
                   <property name="driver" value="com.mysql.jdbc.Driver"/>
                   <property name="url" value="jdbc:mysql://localhost:3306/mybatis_example"/>
                   <property name="username" value="root"/>
                   <property name="password" value=""/>
               </dataSource>
           </environment>
       </environments>
       <mappers>
           <mapper resource="com/example/mappers/EmployeeMapper.xml"/>
       </mappers>
   </configuration>

   This configuration file specifies the database connection details and the SQL statements you want to use.

3. Define data models: MyBatis uses Java objects to represent database tables. You can define data models that map to the database tables you want to work with. Here's an example of how to define a data model:

   public class Employee {
       private int id;
       private String firstName;
       private String lastName;
       private String email;
   
       // getters and setters
   }

4. Write mapper interfaces: Mapper interfaces define the SQL statements you want to execute. You can write mapper interfaces that define methods for each SQL statement, and MyBatis will generate the implementation at runtime. Here's an example of how to write a mapper interface:

   public interface EmployeeMapper {
       @Select("SELECT * FROM employee WHERE id = #{id}")
       Employee findById(int id);
   
       @Insert("INSERT INTO employee (firstName, lastName, email) VALUES (#{firstName}, #{lastName}, #{email})")
       void insert(Employee employee);
   
       @Update("UPDATE employee SET firstName = #{firstName}, lastName = #{lastName}, email = #{email} WHERE id = #{id}")
       void update(Employee employee);
   
       @Delete("DELETE FROM employee WHERE id = #{id}")
       void delete(int id);
   }

5. Use MyBatis in your code: You can use the mapper interfaces to execute SQL statements and perform database operations in your Java code. Here's an example of how to use MyBatis in your code:

   SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
   SqlSession session = sessionFactory.openSession();
   EmployeeMapper employeeMapper = session.getMapper(EmployeeMapper.class);
   
   // insert a new employee
   Employee newEmployee = new Employee();
   newEmployee.setFirstName("John");
   newEmployee.setLastName("Doe");
   newEmployee.setEmail("[email protected]");
   employeeMapper.insert(newEmployee);
   int newEmployeeId = newEmployee.getId();
   
   // find an employee by id
   Employee employee = employeeMapper.findById(newEmployeeId);
   
   // update an employee
   employee.setEmail("[email protected]");
   employeeMapper.update(employee);
   
   // delete an employee
   employeeMapper.delete(newEmployeeId);
   
   session.commit();
   session.close();