请求提供Spring Boot + MyBatis + MyBatis Generator项目搭建完整教程

Hey Danny, let’s walk through a complete, step-by-step MyBatis setup from scratch that should resolve your issues and get your project running smoothly. I’ll use Maven for dependency management (the most widely adopted choice) — if you’re using Gradle, I can tweak the steps later, but let’s start with Maven first.

1. Start with a Fresh Maven Project #

First, create a new Maven project. If you’re using an IDE like IntelliJ or Eclipse, select the "Maven Archetype" option and pick maven-archetype-quickstart to get a basic project structure. Alternatively, you can manually create a pom.xml file in an empty folder with this base setup:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>mybatis-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- MyBatis core dependency (stable version as of 2024) -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.13</version>
        </dependency>
        <!-- MySQL JDBC driver (swap for PostgreSQL/Oracle if needed) -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.33</version>
            <scope>runtime</scope>
        </dependency>
        <!-- JUnit for testing -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <resources>
            <!-- Ensure MyBatis XML files are included in the final build -->
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
        </resources>
    </build>
</project>

Pro tip: Always use the latest stable versions of dependencies — you can check MyBatis’s official docs for updates, but the versions above work reliably for most use cases.

2. Create MyBatis Core Configuration File #

In src/main/resources, make a file named mybatis-config.xml. This is where you’ll set up database connections, transaction rules, and mapper scanning:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- Enable console logging to see generated SQL (super helpful for debugging) -->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <!-- Shorten entity class names for use in XML -->
    <typeAliases>
        <package name="com.example.entity"/>
    </typeAliases>

    <!-- Database environment setup -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/your_db_name?useSSL=false&serverTimezone=UTC"/>
                <property name="username" value="your_db_username"/>
                <property name="password" value="your_db_password"/>
            </dataSource>
        </environment>
    </environments>

    <!-- Tell MyBatis where to find your mapper interfaces/XML files -->
    <mappers>
        <package name="com.example.mapper"/>
    </mappers>
</configuration>

Don’t forget to replace your_db_name, your_db_username, and your_db_password with your actual MySQL credentials. Also, ensure your database has the table you want to work with (we’ll use a user table as an example).

3. Create an Entity Class #

Make a package com.example.entity and add a User class that maps directly to your database table:

package com.example.entity;

public class User {
    private Integer id;
    private String username;
    private String email;

    // Getters and setters
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = id; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }

    // Optional: toString() for debugging
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

Corresponding MySQL table (run this in your database):

CREATE TABLE user (
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE NOT NULL
);

4. Write the Mapper Interface #

Create a package com.example.mapper and add a UserMapper interface. This defines the methods you’ll use to interact with the database:

package com.example.mapper;

import com.example.entity.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper // Marks this as a MyBatis mapper interface
public interface UserMapper {
    // Fetch a user by ID
    User selectUserById(Integer id);

    // Insert a new user
    int insertUser(User user);
}

5. Create the Mapper XML File #

In src/main/resources, make a folder mapper (match your mapper interface’s package structure) and add UserMapper.xml. This is where you’ll write the SQL for your interface methods:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- namespace must exactly match your mapper interface's full class name -->
<mapper namespace="com.example.mapper.UserMapper">

    <!-- Maps SQL columns to entity fields (optional if names match exactly) -->
    <resultMap id="UserResultMap" type="User">
        <id column="id" property="id"/>
        <result column="username" property="username"/>
        <result column="email" property="email"/>
    </resultMap>

    <!-- Matches the selectUserById method in the interface -->
    <select id="selectUserById" resultMap="UserResultMap">
        SELECT id, username, email FROM user WHERE id = #{id}
    </select>

    <!-- Matches the insertUser method; auto-generates and returns the new user ID -->
    <insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
        INSERT INTO user (username, email) VALUES (#{username}, #{email})
    </insert>

</mapper>

Critical check: The namespace must match your mapper interface’s full class name, and each id must exactly match the method name in the interface (case-sensitive!).

6. Test the Setup #

Create a test class in src/test/java/com/example named MyBatisTest:

package com.example;

import com.example.entity.User;
import com.example.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

public class MyBatisTest {

    @Test
    public void testMyBatisWorkflow() throws IOException {
        // Load the MyBatis configuration file
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // Open a session with auto-commit enabled
        try (SqlSession session = sqlSessionFactory.openSession(true)) {
            // Get the mapper instance
            UserMapper mapper = session.getMapper(UserMapper.class);

            // Test inserting a user
            User newUser = new User();
            newUser.setUsername("danny_test");
            newUser.setEmail("danny@example.com");
            int rowsInserted = mapper.insertUser(newUser);
            System.out.println("Rows inserted: " + rowsInserted);
            System.out.println("New user ID: " + newUser.getId());

            // Test fetching the inserted user
            User retrievedUser = mapper.selectUserById(newUser.getId());
            System.out.println("Retrieved user: " + retrievedUser);
        }
    }
}

Run this test — if everything is set up correctly, you’ll see console logs showing the generated SQL, and the test will print the inserted user’s details.

7. Quick Fixes for Common Issues #

If you still hit roadblocks, check these:

• Configuration path: Ensure mybatis-config.xml is in src/main/resources (not nested in a subfolder unless you adjust the path in the test).
• Mapper XML matching: Double-check the namespace and method id in the XML match the interface exactly.
• Dependency conflicts: Run mvn dependency:tree to check for conflicting versions of MyBatis or JDBC drivers.
• Database connection: Verify your MySQL server is running, and the URL/username/password in mybatis-config.xml are correct.
• Mapper scanning: If you don’t use @Mapper on the interface, make sure the mappers section in mybatis-config.xml includes the correct package or XML path.

内容的提问来源于stack exchange，提问作者danny