MyBatis 入门

mybatis 环境搭建

1. 创建 maven 工程并导入坐标
2. 创建实体类和 dao 接口
3. 创建 mybatis 的主配置文件 SqlMapConfig.xml
4. 创建映射配置文件 UserDao.xml

目录结构

.
├── main
│   ├── java
│   │   └── com
│   │       └── swifter
│   │           ├── dao
│   │           │   └── UserDao.java
│   │           └── domain
│   │               └── User.java
│   └── resources
│       ├── SqlMapConfig.xml
│       ├── com
│       │   └── swifter
│       │       └── dao
│       │           └── UserDao.xml
│       └── log4j.properties
└── test
    └── java
        └── com
            └── swifter
                └── test
                    └── MybatisTest.java
​

User.java

public class User implements Serializable {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    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 Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}
​

UserDao.java

public interface UserDao {

    /**
     * 查询所有操作
     * @return
     */
    List<User> findAll();
}
​

SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- mybatis的主配置文件 -->
<configuration>
    <!-- 配置环境 -->
    <environments default="mysql">
        <!-- 配置mysql的环境-->
        <environment id="mysql">
            <!-- 配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源（连接池） -->
            <dataSource type="POOLED">
                <!-- 配置连接数据库的4个基本信息 -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/eesy?characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="jingxuetao"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件 -->
    <mappers>
        <mapper resource="com/swifter/dao/UserDao.xml"/>
    </mappers>
</configuration>
​

UserDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.swifter.dao.UserDao">
    <!--配置查询所有-->
    <select id="findAll" resultType="com.swifter.domain.User">
        select * from user
    </select>
</mapper>
​

pom.xml

<?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.swifter</groupId>
    <artifactId>mybatis_01_start</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.3</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>
</project>
​

注意事项

1. 创建 UserDao.xml 和 UserDao.java 时, 名称是为了和之前的知识保持一致,mybatis 把持久层操作接口名称和映射文件(Mapper) UserMapper 和 UserDao 应该只是名称的区别
2. 在 idea 中创建目录时和包不一样, 包创建 com.swifter.dao 是三级目录, 目录创建是一级目录.
3. mybatis 映射配置文件必须和 dao 接口包结构相同
4. 映射配置文件的 mapper 标签 namespace 属性取值,必须是 dao 接口的全限定类名.
5. 映射配置文件的操作配置,id 属性取值必须是 dao 接口的方法名.

实现 3, 4, 5 后, 在开发中无需再写 dao 的实现类.

--EOF--

新手刚入门.