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