Advantages and limitations of MyBatis reverse engineering

MyBatis is a popular persistence framework that provides reverse engineering functions, which allows developers to automatically generate entity classes, Mapper interfaces and XML based on the table structure in the database mapping file. Reverse engineering is an important feature of MyBatis, which can greatly reduce the developer's workload and improve the maintainability of the code. However, reverse engineering also has some limitations. This article will introduce the advantages and limitations of MyBatis reverse engineering and illustrate it with specific code examples.

First, let's take a look at the advantages of MyBatis reverse engineering. Reverse engineering can automatically generate entity classes, Mapper interfaces and XML mapping files based on the table structure in the database. This way, developers do not need to manually write these codes, thus saving a lot of time and energy. In addition, reverse engineering can also generate code that conforms to specifications, with high code quality and strong readability, which is very helpful for teamwork and long-term maintenance of the project.

Secondly, let's take a look at the limitations of MyBatis reverse engineering. Reverse engineering mainly faces limitations in two aspects: the complexity of the table structure and the customization of reverse engineering. First, if the table structure in the database is very complex, the code generated by reverse engineering may become very large, which will make code management difficult. Secondly, reverse engineering can usually only generate simple addition, deletion, modification and query methods based on the table structure. For some complex business logic, developers also need to manually write code. In addition, the code generated by reverse engineering usually operates on a single table. If multiple table operations are required, developers also need to write the code manually. Therefore, reverse engineering cannot completely replace manual writing of code. It is only a starting point, and developers also need to perform secondary development based on specific needs.

The following is a specific code example that shows how to use the code generated by MyBatis reverse engineering to perform simple database operations.

First, we need to configure reverse engineering related information in the MyBatis configuration file. The specific configuration is as follows:

<!-- 配置逆向工程 -->
<generatorConfiguration>
    <classPathEntry location="/path/to/driver.jar" />
    <context id="MyBatis" targetRuntime="MyBatis3">
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mydatabase"
                        userId="root" password="root" />

        <javaModelGenerator targetPackage="com.example.model"
                            targetProject="/path/to/project/src/main/java" />

        <sqlMapGenerator targetPackage="com.example.mapper"
                         targetProject="/path/to/project/src/main/resources" />

        <javaClientGenerator targetPackage="com.example.mapper"
                             targetProject="/path/to/project/src/main/java"
                             type="XMLMAPPER" />

        <table tableName="user"></table>
    </context>
</generatorConfiguration>

The jdbcConnection tag in the configuration file is used to configure database connection related information, and the javaModelGenerator tag is used to configure the generation path and package name of the entity class , sqlMapGenerator tag is used to configure the path and package name generated by the Mapper XML file, javaClientGenerator tag is used to configure the generated path and package name of the Mapper interface, table tag Used to configure the table name to be reverse engineered to generate code.

Next, we can use the following code to perform database operations:

public interface UserMapper {
    int insert(User record);
    int insertSelective(User record);
}

public class UserDao {
    @Resource
    private UserMapper userMapper;

    public void saveUser(User user) {
        userMapper.insert(user);
    }

    public void updateUser(User user) {
        userMapper.updateByPrimaryKeySelective(user);
    }

    public void deleteUser(int userId) {
        userMapper.deleteByPrimaryKey(userId);
    }

    public User getUserById(int userId) {
        return userMapper.selectByPrimaryKey(userId);
    }
}

public class Main {
    public static void main(String[] args) {
        UserDao userDao = new UserDao();
        User user = new User();
        user.setId(1);
        user.setUsername("John");
        user.setPassword("123456");
        userDao.saveUser(user);

        User savedUser = userDao.getUserById(1);
        System.out.println(savedUser.getUsername());
    }
}

In the above code, UserMapper is the Mapper interface automatically generated through reverse engineering, UserDao is an encapsulation class for database operations. Database operations are performed by calling the methods in UserMapper. The Main class is a test class that demonstrates how to use UserDao to perform database operations.

In summary, MyBatis reverse engineering has the advantages of simplicity, speed, and improved development efficiency, but it also has limitations in table structure complexity and customization. When developers use the code generated by reverse engineering, they need to conduct appropriate secondary development based on specific business needs.

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