MyBatis总结(十八)--#{}取值方式时更加丰富的用法

古城微笑少年丶 2022-05-13 08:26 135阅读 0赞

本文内容来自尚硅谷

> 使用方式
> 
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> 参数位置支持的属性   
> –   javaType、jdbcType、mode、numericScale、 resultMap、typeHandler、jdbcTypeName、expression

这里为可能为空的列名指定jdbcType类型。mybatis连接oracle数据库时，当入参对象为null时mybatis默认传给数据库的值不是null而是other则执行时会报错(使用mysql是不会报错的)

junit

public void test03() throws IOException{
    		
    		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
    		SqlSession openSession = sqlSessionFactory.openSession();
    		
    		try{
    			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
    			Employee employee = new Employee(null, "jerry4",null, "1");
    			mapper.addEmp(employee);
    			System.out.println(employee.getId());
    			openSession.commit();
    		}finally{
    			openSession.close();
    		}
    		
    	}

dao

public Long addEmp(Employee employee);

xml

<insert id="addEmp" databaseId="oracle">
    		<selectKey keyProperty="id" order="BEFORE" resultType="Integer">
    			select EMPLOYEES_SEQ.nextval from dual
    		</selectKey>
    
    		insert into employees(EMPLOYEE_ID,LAST_NAME,EMAIL)
    		values(#{id},#{lastName},#{email})
    	</insert>

此时连接oracle时回报语法错误。

xml应该如下写法

<insert id="addEmp" databaseId="oracle">
    		<selectKey keyProperty="id" order="BEFORE" resultType="Integer">
    			select EMPLOYEES_SEQ.nextval from dual
    		</selectKey>
    		insert into employees(EMPLOYEE_ID,LAST_NAME,EMAIL)
    		values(#{id},#{lastName},#{email ,jdbcType=NULL})
    	</insert>

这就是jdbctype的使用实例。意思是当email值为null时将把值设置成null而不是other

[70]: /images/20220513/4238db0c200a4b57851122e02255859e.png
[70 1]: /images/20220513/b06e4219f2734464b023010fa0958ab6.png