增加null

oracle：如果插入的欄位是Null，提示錯誤:Other而不是null

mysql：如果插入的欄位是Null，正常執行(沒有約束)

原因：各個資料庫在mybatis中對各種資料型別的預設值不一致

　　mybatis中，jdbcTypeForNull(如果是null)，則預設值是Other。

　　Other來說，Mysql能夠處理（NULL），但是Oracle不行

解決：

　　Oracle：null->Other,需要手工告訴Oracle：other為null

　　a.修改具體的sql標籤

當某個資料型別oracle無法處理時，告訴它預設值null

注意此時設定的#{stuName,jdbcType=NULL}不會影響正常的賦值

src\org\myy\mapper\studentMapper.xml

    <insert id="addStudent" parameterType="Student" databaseId="oracle">
        <selectKey keyProperty="stuNo" resultType="Integer" order="AFTER">
            select myseq.currval from dual
        </selectKey>
        insert into student1(stuno,stuname,stuage,graname)
        values(myseq.nextval,#{stuName,jdbcType
 
=NULL},#{stuAge},#{graName})
    </insert>

　　b.配置mybatis全域性配置檔案conf.xml（推薦）

src\conf.xml

 <settings>
        <setting name="jdbcTypeForNull" value="NULL"/>
 </settings>

返回值為HashMap的情況

src\org\myy\mapper\studentMapper.xml

    <select id="queryStudentOutByHashMap" parameterType="int"
            resultType
 
="HashMap">
        select stuNo "no",stuName "name",stuAge "age"
        from  student1 where stuNo=#{stuNo}
    </select>

其中stuNo是資料庫的欄位名

"no"是stuNo的別名，用於在map中get值時使用（作為map的key）map.get("no")

如果不加別名，map的key就是欄位名

src\org\myy\mapper\StudentMapper.java

HashMap<String,Object> queryStudentOutByHashMap(int stuNo);

src\org\myy\test\Test.java

        //Connection - SqlSession操作Mybatis
        //conf.xml->reader
        Reader reader = Resources.getResourceAsReader("conf.xml");
        //reader->sqlSession

        //可以通過build的第二引數 指定資料庫環境
        SqlSessionFactory sessionFactory=new SqlSessionFactoryBuilder().build(reader,"devOracle");
        SqlSession session = sessionFactory.openSession();

        StudentMapper studentMapper=session.getMapper(StudentMapper.class);

        HashMap<String, Object> studentMap = studentMapper.queryStudentOutByHashMap(1);
        System.out.println(studentMap.get("no")+","+studentMap.get("name")+","+studentMap.get("age"));
        System.out.println(studentMap);
        session.close();

key:id　　value:Student

src\org\myy\mapper\studentMapper.xml

    <select id="queryStudentsByHashMap"
            resultType="HashMap">
        select stuNo,stuName,stuAge from student1
    </select>

src\org\myy\mapper\StudentMapper.java

    //程式根據select的返回值,知道map的value就是Student，根據@MapKey("STUNO")知道map的key是stuNo

　　@MapKey("STUNO")//Oracle的元資料(表名、欄位名)都是大寫
　　HashMap<Integer,Student> queryStudentsByHashMap();

src\org\myy\test\Test.java

        //Connection - SqlSession操作Mybatis
        //conf.xml->reader
        Reader reader = Resources.getResourceAsReader("conf.xml");
        //reader->sqlSession

        //可以通過build的第二引數 指定資料庫環境
        SqlSessionFactory sessionFactory=new SqlSessionFactoryBuilder().build(reader,"devOracle");
        SqlSession session = sessionFactory.openSession();

        StudentMapper studentMapper=session.getMapper(StudentMapper.class);

        HashMap<Integer, Student> studentsMap = studentMapper.queryStudentsByHashMap();
        //System.out.println(studentMap.get("no")+","+studentMap.get("name")+","+studentMap.get("age"));
        System.out.println(studentsMap);

        session.close();