Mybatis 返回值配置理解 - 返回值是浮点数 BigDecimal 或整数 Integer的配置 - 返回指定实体类格式的 List 数组

前提

Mybatis报错： A query was run and no Result Maps were found for the Mapped Statement

mybatis中的所有查询标签，都必须返回resultType或者resultMap的值，否则就会报如上错误的，其实仔细看看因为报错原因的意思就好了

1. 返回整形数值

TestMapper.xml 演示：

<select id="getReturnNum" resultType="java.lang.Integer">
        SELECT COUNT(1)
        FROM test_table
select>

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Java 调用演示：

@Autowired
private TestMapper testMapper;

Integer mycount = testMapper.getReturnNum();
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2. 返回值 BigDecimal 浮点数 金额类型

TestMapper.xml 演示：

<select id="getReturnAmount" resultType="java.math.BigDecimal">
        SELECT IFNULL(SUM(mymoney), 0.00)
        FROM test_table
select>
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Java 调用演示：

@Autowired
private TestMapper testMapper;

Integer mycount = testMapper.getReturnAmount();
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3. 返回指定实体类格式的 List 数组

TestMapper.xml 演示：

<select id="getReturnList" resultType="com.test.entity.MyEntity">
        SELECT *
        FROM test_table
select>
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Java 调用演示：

import com.test.entity.MyEntity;

@Autowired
private TestMapper testMapper;

List<MyEntity> myList = testMapper.getReturnList();
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参考链接

Mybatis报错： A query was run and no Result Maps were found for the Mapped Statement