Mybatis系列二十二：自定义类型处理

妖狐艹你老母 2022-02-13 09:29 350阅读 0赞

自定义TypeHandler处理枚举  
 我们可以通过自定义TypeHandler的形式来在设置参数或者取出结果集的时候自定义参数封装策略。  
步骤：  
 1、实现TypeHandler接口或者继承BaseTypeHandler  
 2、使用@MappedTypes定义处理的java类型 使用@MappedJdbcTypes定义jdbcType类型  
 3、在自定义结果集标签或者参数处理的时候声明使用自定义TypeHandler进行处理 或者在全局配置TypeHandler要处理的javaType  
自定义类型处理：  
1、在tbl\_employee表中添加字段

alter table tbl_employee add empStatus varchar(11)

2、在Employee中添加属性

//员工状态
    	private EmpStatus empStatus=EmpStatus.LOGOUT;
        public EmpStatus getEmpStatus() {
            return empStatus;
        }
        public void setEmpStatus(EmpStatus empStatus) {
            this.empStatus = empStatus;
        }

3、修改EmployeeMapper.xml

<insert id="addEmp" useGeneratedKeys="true" keyProperty="id">
    		insert into tbl_employee(last_name,email,gender,empStatus)
    		values(#{lastName},#{email},#{gender},#{empStatus})
    	</insert>

3、创建一个枚举类

/**
     * 希望数据库保存的是100,200这些状态码，而不是默认0,1或者枚举的名
     * @author lizq
     *
     */
    public enum EmpStatus {
    	LOGIN(100,"用户登录"),LOGOUT(200,"用户登出"),REMOVE(300,"用户不存在");
    	
    	
    	private Integer code;
    	private String msg;
    	private EmpStatus(Integer code,String msg){
    		this.code = code;
    		this.msg = msg;
    	}
    	public Integer getCode() {
    		return code;
    	}
    	
    	public void setCode(Integer code) {
    		this.code = code;
    	}
    	public String getMsg() {
    		return msg;
    	}
    	public void setMsg(String msg) {
    		this.msg = msg;
    	}
    	
    	//按照状态码返回枚举对象
    	public static EmpStatus getEmpStatusByCode(Integer code){
    		switch (code) {
    			case 100:
    				return LOGIN;
    			case 200:
    				return LOGOUT;	
    			case 300:
    				return REMOVE;
    			default:
    				return LOGOUT;
    		}
    	}
    }

4、自定义TypeHandler

/**
     * 1、实现TypeHandler接口。或者继承BaseTypeHandler
     * @author lizq
     *
     */
    public class MyEnumEmpStatusTypeHandler implements TypeHandler<EmpStatus> {
    
    	/**
    	 * 定义当前数据如何保存到数据库中
    	 */
    	@Override
    	public void setParameter(PreparedStatement ps, int i, EmpStatus parameter,
    			JdbcType jdbcType) throws SQLException {
    		// TODO Auto-generated method stub
    		System.out.println("要保存的状态码："+parameter.getCode());
    		ps.setString(i, parameter.getCode().toString());
    	}
    
    	@Override
    	public EmpStatus getResult(ResultSet rs, String columnName)
    			throws SQLException {
    		// TODO Auto-generated method stub
    		//需要根据从数据库中拿到的枚举的状态码返回一个枚举对象
    		int code = rs.getInt(columnName);
    		System.out.println("从数据库中获取的状态码："+code);
    		EmpStatus status = EmpStatus.getEmpStatusByCode(code);
    		return status;
    	}
    
    	@Override
    	public EmpStatus getResult(ResultSet rs, int columnIndex)
    			throws SQLException {
    		// TODO Auto-generated method stub
    		int code = rs.getInt(columnIndex);
    		System.out.println("从数据库中获取的状态码："+code);
    		EmpStatus status = EmpStatus.getEmpStatusByCode(code);
    		return status;
    	}
    
    	@Override
    	public EmpStatus getResult(CallableStatement cs, int columnIndex)
    			throws SQLException {
    		// TODO Auto-generated method stub
    		int code = cs.getInt(columnIndex);
    		System.out.println("从数据库中获取的状态码："+code);
    		EmpStatus status = EmpStatus.getEmpStatusByCode(code);
    		return status;
    	}
    
    }

5、在全局配置文件中配置我们自定义的类型处理器

<typeHandlers>
    		
    		<typeHandler handler="com.atguigu.mybatis.typehandler.MyEnumEmpStatusTypeHandler" javaType="com.atguigu.mybatis.bean.EmpStatus"/>
    		
    	</typeHandlers>

测试：

@Test
    	public void testEnumUse(){
    		EmpStatus login = EmpStatus.LOGIN;
    		System.out.println("枚举的索引："+login.ordinal());
    		System.out.println("枚举的名字："+login.name());
    		
    		System.out.println("枚举的状态码："+login.getCode());
    		System.out.println("枚举的提示消息："+login.getMsg());
    	}
    	
    	/**
    	 * 默认mybatis在处理枚举对象的时候保存的是枚举的名字：EnumTypeHandler
    	 * 改变使用：EnumOrdinalTypeHandler：
    	 * @throws IOException
    	 */
    	@Test
    	public void testEnum() throws IOException{
    		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
    		SqlSession openSession = sqlSessionFactory.openSession();
    		try{
    			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
    			Employee employee = new Employee("test_enum", "enum@atguigu.com","1");
    			mapper.addEmp(employee);
    			System.out.println("保存成功"+employee.getId());
    			openSession.commit();
    			Employee empById = mapper.getEmpById(employee.getId());
    			System.out.println(empById.getEmpStatus());
    		}finally{
    			openSession.close();
    		}
    	}

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