关于selectKey

1.首先我们要做的是在pom.xml中配置3个点

<!--MyBatis核心jar包--><dependency>    <groupId>org.mybatis</groupId>    <artifactId>mybatis</artifactId>    <version>3.2.2</version></dependency><!--MySQL配置--><dependency>    <groupId>mysql</groupId>    <artifactId>mysql-connector-java</artifactId>    <version>5.1.25</version></dependency><build>    <plugins>        <plugin>            <groupId>org.apache.maven.plugins</groupId>            <artifactId>maven-compiler-plugin</artifactId>            <configuration>                <source>1.8</source>                <target>1.8</target>                <encoding>utf8</encoding>            </configuration>        </plugin>    </plugins></build>

2.接下来 我们要搭好练习项目架构（如图所示：）

3.现在我们来配置Mybatis.xml文件

<?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">
<configuration>
    <propertiesresource="config.properties">
    </properties>
    <environmentsdefault="development">
        <environmentid="development">
            <transactionManagertype="JDBC"/>
            <dataSourcetype="POOLED">
                <propertyname="driver"value="${driver}"/>
                <propertyname="url"value="${url}"/>
                <propertyname="username"value="${username}"/>
                <propertyname="password"value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapperclass="haha.UserDao"/>
        <mapperresource="user.xml"/>
    </mappers>
</configuration>

4.创建实体类User

User有三个属性：name，age和id，重写toString()方法便于调试。

 

public class User {
    String name;
    Integer age;
    Integer id;

    public User(){}
public User(String name,intage){
    this.name=name;
    this.age=age;
}

 

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name= name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age= age;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id= id;
    }

    @Override
    publicString toString() {
        return String.format("(id:%d,name:%s,age:%d)",id, name,age);
    }
}

5.实现UserDao接口

UserDao接口有两个功能：插入、查询全部

 

public interface UserDAO {
    @Insert("insert into user(name,age) value (#{name},#{age})")
    int insert_withoutPrimaryKey(@Param("name") String name,@Param("age")int age);

    int insert_useGeneratedKey(@Param("user") User user);

    int insert_selectKey(@Param("user") User user);

    @Insert("insert into user(name,age) value(#{user.name},#{user.age})")
    @SelectKey(statement = "select last_insert_id()",keyProperty = "user.id",before = false,resultType =int.class)
    int insert_selectKeyAnotation(@Param("user") User user);

    @Select("select*from user")
    List<User> getAll();
}

6.User.xml文件

 

<?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">
<mappernamespace="haha.UserDao">
    <insertid="insert_useGeneratedKey"parameterType="haha.User"
            useGeneratedKeys="true"keyProperty="user.id">
        insert into user set id=#{user.id},name=#{user.name},age=#{user.age}
    </insert>
    <insertid="insert_selectKey"parameterType="haha.User">
        <selectKeykeyProperty="user.id"keyColumn="id"order="AFTER"resultType="int">
            SELECT last_insert_id()
        </selectKey>
        insert into user(name,age) VALUE (#{user.name},#{user.age})
    </insert>
</mapper>

7.编写测试类

packagehaha;
importorg.apache.ibatis.io.Resources;
importorg.apache.ibatis.session.SqlSession;
importorg.apache.ibatis.session.SqlSessionFactory;
importorg.apache.ibatis.session.SqlSessionFactoryBuilder;

importjava.io.IOException;
importjava.io.InputStream;
importjava.util.List;

public classUserService {

public static voidmain(String[] args)throwsIOException {
    String resource ="mybatis.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactoryBuilder builder =newSqlSessionFactoryBuilder();
    SqlSessionFactory factory = builder.build(inputStream);
    SqlSession session = factory.openSession();
    UserDao dao = session.getMapper(UserDao.class);

    //使用默认主键
    intaffectedRows = dao.insert_withoutPrimaryKey("张三",25);
    System.out.println(affectedRows);

    //使用useGeneratedKey，将主键注入到user.id中
    User u =newUser("李四",17);
    affectedRows = dao.insert_useGeneratedKey(u);
    System.out.println(affectedRows + " "+ u.getId());

    //使用selectKey执行在插入之前或之后执行查询语句
    affectedRows = dao.insert_selectKey(u);
    System.out.println(affectedRows + " "+ u.getId());

    //使用selectKey注解的方式
    affectedRows = dao.insert_selectKeyAnotation(u);
    System.out.println(affectedRows + " "+ u.getId());
    session.commit();
    List<User> a = dao.getAll();
    a.forEach(System.out::println);
}
}