Mybatis 查询数据返回基本类型数组

末蓝、 2022-06-16 03:59 284阅读 0赞

**1. mybatis 查询数据的时候返回类型不能是基本类型的数组。如果是基本类型的数组会报类型转换错误。**

//StudentMapper
    public interface StudentMapper {
        int[] getAllStudentIds();
    }
    
    //StudentMapper.xml
    <?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">
    <mapper namespace="com.morris.dao.StudentMapper">
        <resultMap id="orderInfo" type="com.morris.po.OrderInfo">
            <id property="id" column="order_id"/>
            <result property="orderNumber" column="order_number"/>
            <association property="orderAddress" javaType="com.morris.po.OrderAddress">
                <result property="region" column="region"/>
                <result property="district" column="district"/>
                <result property="city" column="city"/>
                <result property="street" column="street"/>
            </association>
        </resultMap>
    
        <select id="getAllStudentIds" resultType="int">
            select id
                from student;
        </select>
    
    </mapper>
    
    //验证
     public static void main(String [] args) {
            SqlSession session = getSqlSession();
            StudentMapper sm = session.getMapper(StudentMapper.class);
            int[] ids = sm.getAllStudentIds();
            for (int i : ids) {
                System.out.println(i);
            }
    }
    运行程序会抛出ClassCastException
    Exception in thread "main" java.lang.ClassCastException: [I cannot be cast to [Ljava.lang.Object;
        at org.apache.ibatis.binding.MapperMethod.convertToArray(MapperMethod.java:141)
        at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:124)
        at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)
        at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
        at com.sun.proxy.$Proxy0.getAllStudentIds(Unknown Source)
        at com.morris.util.MybatisUtil.main(MybatisUtil.java:44)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

1.  解决方案  
    
    
    1.  接口中返回数据 用包装类来接收  
        
        
        1.  `Integer[] getAllStudentIds();`
        2.  xml 配置中resultType=”int” 改成 resultType=”java.lang.Integer”
    2.  接口中用list 来接收  
        
        
        1.  `List<Integer> getAllStudentIds();`
        2.  xml 配置中resultType=”int” 改成 resultType=”java.lang.Integer”