Java学习-MyBatis学习(二)

代码下载

MyBatis核心配置文件

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://192.168.29.201:3306/mybatis
jdbc.username=root
jdbc.password=123456

<configuration>
    
    	 
    <properties resources="jdbc.properties/>
    
    
        
	
        
        <package name="com.lotus.mybatis.pojo"/>
    typeAliases>
    <environments default="development">   
        <environment id="development">
        <! -- 
         type：JDBC | MANAGED
         JDBC:表示当前环境中，执行SQL时，使用的是JDBC中原生的事务管理方式，事务提交和回滚需要手动处理
         MANAGED：表示被管理，例如Spring
        -->
            <transactionManager type="JDBC"/>
            
            <dataSource type="POOLED">
            	
                <property name="driver" value="${jdbc.driver}"/>
            	
                <property name="url" value="${jdbc.url}"/>
                
                 <property name="username" value="${jdbc.username}"/>
                
                <property name="password" value="${jdbc.password}"/>
            dataSource>
        environment>
    environments>
    
    <mappers>
        <mapper resource="mappers/UserMapper.xml"/>
    mappers>
configuration>



<mappers>

        
        <package name="com.lotus.mybatis.mapper"/>
    mappers>

设置配置文件模板

• ①复制要创建模板的配置文件内容
• ②
  
• ③
  

MyBatis获取参数值

• Mybatis获取参数值的两种方式：${} 和 #{}
• ${}本质就是字符串拼接，#{}本质是占位符赋值
• ${}使用字符串拼接的方式拼接SQL，若为字符串类型或日期类型的字段进行赋值时，需要手动加单引号;但#{}使用占位符赋值的方式拼接SQL，此时为字符串类型或日期类型的字段进行赋值时，可以自动添加单引号

//pojo
public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    private String sex;
    private String email;

    public User() {
    }

    public User(Integer id, String username, String password, Integer age, String sex, String email) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
        this.sex = sex;
        this.email = email;
    }

    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 getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

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

    public String getSex() {
        return sex;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "com.lotus.mybatis.pojo.User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

//SqlSession获取封装功能类
public class SqlSessionUtils {
    public static SqlSession getSqlSession() {
        SqlSession sqlSession = null;
        try {
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
            sqlSession = sqlSessionFactory.openSession(true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sqlSession;
    }
}

单个字面量类型的参数

• 若mapper接口中的方法参数为单个字面量类型，可以使用KaTeX parse error: Expected 'EOF', got '#' at position 4: {}或#̲{}以任意名称获取参数的值，*…{}手动加单引号**

public interface ParameterMapper {
    /**
     * 根据用户名查询用户信息
     */
    User getUserByUsername(String username);
}

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lotus.mybatis.mapper.ParameterMapper">
    
    <select id="getUserByUsername" resultType="com.lotus.mybatis.pojo.User">
        
        select * from t_user where username='${username}'
    select>
mapper>

@Test
    public void testGetUserByUsername() throws IOException {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        User user = mapper.getUserByUsername("dizzy");
        System.out.println(user);
    }

多个字面量类型的参数

• 若mapper接口中的方法参数为多个时，MyBatis自动将这些参数放在一个Map集合中，以arg0,arg1…为键，以参数为值，以param1,param2…为键，以参数为值，只需要通过KaTeX parse error: Expected 'EOF', got '#' at position 4: {}或#̲{}访问map集合的键就可以获…{}需手动加单引号**

public interface ParameterMapper {
    /**
     * 验证登录
     */
    User checkLogin(String username,String password);
}

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lotus.mybatis.mapper.ParameterMapper">
    
    <select id="checkLogin" resultType="User">
        
        
        select * from t_user where username='${arg0}' and password='${param2}'
    select>
mapper>

 @Test
    public void testCheckLogin() throws IOException {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        User user = mapper.checkLogin("dizzy","12345");
        System.out.println(user);
    }

map集合类型的参数

• 若mapper接口中的方法参数为多个时，可手动创建map集合，将这些数据放在map中，只需通过KaTeX parse error: Expected 'EOF', got '#' at position 4: {}或#̲{}访问map集合的键就可以获…{}需手动加单引号**

/**
     * 验证登录(参数为map)
     */
    User checkLoginByMap(Map<String,Object> map);

    <select id="checkLoginByMap" resultType="User">
        select * from t_user where username='${username}' and password='${password}'
    select>

@Test
    public void testCheckLoginByMap() throws IOException {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        Map<String,Object> map = new HashMap<>();
        map.put("arg0","dizzy");
        map.put("arg1","12345");
        map.put("param1","dizzy");
        map.put("param2","12345");
        map.put("username","dizzy");
        map.put("password","12345");
        User user = mapper.checkLoginByMap(map);
        System.out.println(user);
    }

实体类类型的参数(重点)

• 若mapper接口中的方法参数为实体类时，只需通过KaTeX parse error: Expected 'EOF', got '#' at position 4: {}或#̲{}访问实体类属性值的方式就可…{}需手动加单引号**

/**
     * 添加用户信息
     */
    int insertUser(User user);

    <insert id="insertUser">
        insert into t_user values(null,#{username},#{password},#{age},#{sex},#{email})
    insert>

 @Test
    public void testInsertUser() throws IOException {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        int res = mapper.insertUser(new User(null,"water","123456",11,"男","[email protected]"));
        System.out.println(res);
    }

使用注解@param命名参数(重点)

• 若mapper接口中的方法参数使用@param修饰，MyBatis自动将这些参数放在一个Map集合中，以@param注解的值为键，以参数为值，以param1,param2…为键，以参数为值，只需要通过KaTeX parse error: Expected 'EOF', got '#' at position 4: {}或#̲{}访问map集合的键就可以获…{}需手动加单引号**

 /**
     * 验证登录(使用@param)
     */
    User checkLoginByParam(@Param("username") String username, @Param("password") String password);

    <select id="checkLoginByParam" resultType="User">
        select * from t_user where username=#{username} and password=#{password}
    select>

 @Test
    public void testCheckLoginByParam() throws IOException {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
        User user = mapper.checkLoginByParam("water","123456");
        System.out.println(user);
    }