Mybatis的失误填坑-java.lang.Integer cannot be cast to java.lang.String

最新推荐文章于 2025-07-03 09:01:40 发布

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最新推荐文章于 2025-07-03 09:01:40 发布

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CC 4.0 BY-SA版权

文章标签： java 数据库

原文链接：http://www.cnblogs.com/bwcode/p/6272993.html

本文通过一个简单的MyBatis CRUD示例介绍了如何处理数据库查询结果，并解决了查询结果中整数类型字段转换为字符串类型的问题。

Mybatis的CRUD小Demo

为方便查看每次的增删改结果，封装了查询，用来显示数据库的记录；

    public static void showInfo(){
        SqlSession session = getSqlSesion();
        String sql = "me.gacl.mapping.userMapper.getUsers";
        List<Map<String,String>> users = session.selectList(sql);
        for(Map<String,String> u : users){
            System.out.println("id:" + u.get("id").toString() + "--NAME:" + u.get("NAME"));
        }
        session.close();
    }

id字段数据库数据类型是int，返回Map接收查询结果，接收时使用了List<Map<String,String>>接收结果集；

     <select id="getUsers" resultType="Map">
         select * from users
     </select>

然后一直报错：

java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
    at me.gacl.util.MyBatisUtil.showInfo(MyBatisUtil.java:46)
    at me.gacl.test.TestDBUtil.upUser(TestDBUtil.java:71)
    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 org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

最终改了接收结果集才解决问题：

    public static void showInfo(){
        SqlSession session = getSqlSesion();
        String sql = "me.gacl.mapping.userMapper.getUsers";
        List<Map<String,Object>> users = session.selectList(sql);
        for(Map<String,Object> u : users){
            System.out.println("id:" + u.get("id").toString() + "--NAME:" + u.get("NAME"));
        }
        session.close();
    }

做一个随笔记录，纪念自己的坑。

转载于:https://www.cnblogs.com/bwcode/p/6272993.html