MyBatis学习之简单增删改查操作、MyBatis存储过程、MyBatis分页、MyBatis一对一、MyBatis一对多

 一、用到的实体类如下：

Student.java

package com.company.entity;

import java.io.Serializable;
import java.util.Date;

public class Student implements Serializable{

    private static final long serialVersionUID = 1L;
    private int id;
    private String name;
    private Date birth;
    private Group group;


    public Group getGroup() {
        return group;
    }
    public void setGroup(Group group) {
        this.group = group;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Date getBirth() {
        return birth;
    }
    public void setBirth(Date birth) {
        this.birth = birth;
    }
    @Override
    public String toString() {
        return "Student [birth=" + birth + ", group=" + group + ", id=" + id
                + ", name=" + name + "]";
    }


}

Group.java

package com.company.entity;

import java.util.List;

public class Group {
    private int id;
    private String name;
    private String position;
    private List<Student> students;


    public List<Student> getStudents() {
        return students;
    }
    public void setStudents(List<Student> students) {
        this.students = students;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPosition() {
        return position;
    }
    public void setPosition(String position) {
        this.position = position;
    }
    @Override
    public String toString() {
        return "Group [id=" + id + ", name=" + name + ", position=" + position
                + "]";
    }

}

二、实体对应的表结构

student表:

create table student(

id  int primary key,

name varchar2(20),

birth date,

group_id int references g_group(g_id));

g_group表:

create  table g_group(

g_id int primary key,

g_name varchar2(20),

g_position varchar2(30));

sequence:

create sequence student_id_sequence;

create sequence group_id_sequence;

三、Student和Group的映射文件如下，你可以在映射文件中找到，关于MyBatis的增删改查操作，MyBatis调用存储过程，MyBatis分页以及MyBatis对一对一、多对多的处理

xml文件中都标有注释，看的时候配合下面的具体实现看，虽然有点乱

student.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.company.dao.IStudentDAO">

    <!-- mybatis缓存 -->
    <cache eviction="LRU" flushInterval="600000" size="1024" readOnly="false" />

    <!-- sql标签用来定义一些可以被重用的sql语句或字段或片段等 -->
    <sql id="studentColumns">select id,name,birth from student</sql>

    <!-- 此处获得多对一的关系 ,但就单条记录而言却是一对一的关系，所以一对一的写法跟此相同-->
    <resultMap type="Student" id="getStudentAndGroup" >
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="birth" property="birth"/>
        <association property="group" column="group_id" javaType="Group">
            <id column="g_id" property="id"/>
            <result column="g_name" property="name"/>
            <result column="g_position" property="position"/>
        </association>
    </resultMap>
    <select id="many2one" resultMap="getStudentAndGroup" parameterType="int" >
        select s.id,s.name,s.birth,s.group_id,g.g_id,g.g_name,g.g_position
        from student s
        left join g_group g on s.group_id = g.g_id
        where s.id = #{id}
    </select>


    <!-- 意图是获得一个学生，并且获得该学生所属的组，跟上面的意思差不多 ,用association的select属性-->
    <!-- 于上面的相比个人感觉上面的效率要高些，因为上面只有一条sql语句 -->
    <resultMap type="Student" id="getStudentAndGroupUseSelectMap">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="birth" property="birth"/>
        <association property="group" column="group_id" javaType="Group" select="selectGroup" />
    </resultMap>
    <select id="getStudentAndGroupUseSelect" resultMap="getStudentAndGroupUseSelectMap" parameterType="int">
        select *
        from student
        where id = #{id}
    </select>
    <select id="selectGroup" resultType="Group" parameterType="int" flushCache="false" useCache="true"><!-- 此处实用缓存 -->
        select g_id as id, g_name as name, g_position as position
        from g_group
        where g_id = #{id}
    </select>

    <!-- 动态sql语句 的测试dynamic sql-->
    <select id="getStudentBySomeCondition" parameterType="Student" resultType="Student">
        select *
        from student
        <where>
            <if test="id != null">
                id>2
            </if>
            <if test="name != null">
                and name like '%g%'
            </if>
        </where>
    </select>

    <!-- MyBatis调用存储过程 -->
    <resultMap type="Student" id="studentMap">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="birth" property="birth"/>
    </resultMap>
    <select id="getAllUser" statementType="CALLABLE" >
        {call get_all_student(#{students ,mode=OUT, jdbcType=CURSOR, javaType=ResultSet, resultMap=studentMap} )}
    </select>


    <!-- MyBatis向student表中插入一条数据 -->
    <insert id="add" parameterType="Student" keyColumn="id">
        <selectKey keyProperty="id" order="BEFORE" resultType="int">
            select stu_id_sequence.nextval from dual
        </selectKey>
        insert into student(id,name,birth) values(#{id},#{name},#{birth})
    </insert>

    <!-- 根据id获得学生的信息 -->
    <select id="getById" parameterType="int" resultType="Student">
        <include refid="studentColumns"/> where id=#{id}
    </select>

    <!-- 此处的实现方法是一个分页的原型,请查看IStudentDAOImpl.java中的调用方法 -->
    <select id="getAllStudent" resultMap="studentMap">
        <include refid="studentColumns"/> order by id<!--此处是引用了上面预定义好的sql语句-->
    </select>


</mapper>

group.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.company.dao.IGroupDAO">



    <resultMap type="Group" id="groupResultMap" >
        <id column="g_id" property="id"/>
        <result column="g_name" property="name"/>
        <result column="g_position" property="position"/>
    </resultMap>
    <sql id="getALl">select * from</sql>

    <!-- 意图想通过获得组和组中的所有student,此处相当于one2many -->
    <resultMap type="Group" id="getGroupAndStudents">
        <id column="g_id" property="id"/>
        <result column="g_name" property="name"/>
        <result column="g_position" property="position"/>
        <collection property="students" ofType="Student" column="group_id"><!-- 注意此处的group_id是student表的外键 -->
            <id column="id" property="id"/>
            <result column="name" property="name"/>
            <result column="birth" property="birth"/>
        </collection>
    </resultMap>






    <select id="getById" parameterType="int" resultMap="getGroupAndStudents">
        select g.g_id,g.g_name,g.g_position,s.id,s.name,s.birth ,s.group_id
        from g_group g
        left join student s on g.g_id = s.group_id
        where g.g_id = #{id}
    </select>

    <!--
    <select id="getById" parameterType="int" resultType="Group">
        select g_id as id, g_name as name, g_position as position from g_group where g_id=#{id}
    </select>
     -->
    <select id="getByIdResultMap" parameterType="_int" resultMap="groupResultMap">
        select g_id ,g_name, g_position  from g_group where g_id=#{id}
    </select>
    <delete id="deleteById" parameterType="_int" timeout="1000">
        delete from g_group where g_id=#{id}
    </delete>
    <insert id="add" parameterType="Group">
        insert into g_group(g_id, g_name, g_position)
        values(#{id}, #{name}, #{position})
    </insert>

</mapper>

 

四、接口IStudentDAO.java和IGroupDAO.java中定义了IStudentDAOImpl.java和IGroupDAOImpl.java中需要实现的方法

IStudentDAO.java

package com.company.dao;

import java.util.List;

import com.company.entity.Student;

public interface IStudentDAO {
    /**
     * 增加一个学生
     * @param student
     */
    public void add(Student student);

    /**
     * 根据学生的Id删除学生
     * @param id
     */
    public void deleteById(int id);

    /**
     * 通过学生的id获得学生的信息
     * @param id
     * @return
     */
    public Student getById(int id);

    /**
     * 更新学生信息
     * @param student
     */
    public void update(Student student);

    /**
     * 此处是MyBatis的分页查询
     * @return
     */
    public List<Student> getAllStudent();

    /**
     * 多对一
     * @param id
     * @return
     */
    public Student many2one(int id);

    /**
     * 获得学生的信息，并且获得该学生所属的组的信息
     * @param id
     * @return
     */
    public Student getStudentAndGroupUseSelect(int id);

    /**
     * 动态sql
     * @param student
     * @return
     */
    public List<Student> getStudentBySomeCondition(Student student);

    /**
     * 获得所有的学生信息，此处是调用在数据库中存储过程
     * @return
     */
    public List<Student> getAllUser();
}

对应的实现类IStudentDAOImpl.java如下：

package com.company.dao.impl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.company.dao.IStudentDAO;
import com.company.entity.Student;
import com.company.util.DBUtil;

public class IStudentDAOImpl implements IStudentDAO {



    public void add(Student student) {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        try{
            IStudentDAO dao = session.getMapper(IStudentDAO.class);
            dao.add(student);
            session.commit();
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
    }

    public void deleteById(int id) {

    }

    public Student getById(int id) {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        Student student = null;
        try{
            IStudentDAO dao = session.getMapper(IStudentDAO.class);
            student = dao.getById(id);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return student;
    }

    public void update(Student student) {

    }


    public List<Student> getStudentsByGroupId(int groupId) {
        return null;
    }

    /**
     * 测试selectList，分页的原型
     * @author king
     * @return students
     * @serialData 2011-7-29
     */
    public List<Student> getAllStudent() {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        List<Student> students = new ArrayList<Student>();
        try{
            RowBounds rb = new RowBounds(1,6);//RowBounds的下标是从0开始，表示第一条记录，此表示从第二条记录开始，取6条记录
            students = session.selectList("com.company.dao.IStudentDAO.getAllStudent", null, rb);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return students;
    }

    public Student many2one(int id) {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        Student student = null;
        try{
            IStudentDAO dao = session.getMapper(IStudentDAO.class);
            student = dao.many2one(id);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return student;

    }

    public Student getStudentAndGroupUseSelect(int id){
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        Student student = null;
        try{
            IStudentDAO dao = session.getMapper(IStudentDAO.class);
            student = dao.getStudentAndGroupUseSelect(id);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return student;
    }

    public List<Student> getStudentBySomeCondition(Student student){
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        List<Student> students = new ArrayList<Student>();
        try{
            IStudentDAO dao = session.getMapper(IStudentDAO.class);
            students = dao.getStudentBySomeCondition(student);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return students;
    }

    public List<Student> getAllUser(){
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        List<Student> students = new ArrayList<Student>();
        try{
            Map<String,List<Student>> map = new HashMap<String,List<Student>>();
            session.selectOne("com.company.dao.IStudentDAO.getAllUser", map);
            students =  (List<Student>) map.get("students");
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return students;
    }

    public static void main(String[] args) {
        Student student = new Student();
        IStudentDAOImpl impl = new IStudentDAOImpl();
        List<Student> students = impl.getAllStudent();
        for(Student s : students) {
            System.out.println(s);
        }
    }
}

 

IGroupDAO.java代码如下：

package com.company.dao;

import com.company.entity.Group;

public interface IGroupDAO {
    /**
     * 增加一个组
     * @param group
     */
    public void add(Group group);
    /**
     * 根据id删除组
     * @param id
     */
    public void deleteById(int id);

    /**
     * 此方法是通过id获得一个组的信息，并且获得该组下面的所有的学生信息
     * @param id
     * @return
     */
    public Group getById(int id);


    /**
     * 此方法是测试如何设定ResultMap的方式来从数据库中获得Group
     * @param id
     * @return
     */
    public Group getByIdResultMap(int id);


    public void update(Group group);



}

IGroupDAO.java对应的实现类IGroupDAOImpl.java如下 ：

package com.company.dao.impl;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.company.dao.IGroupDAO;
import com.company.entity.Group;
import com.company.entity.Student;
import com.company.util.DBUtil;

public class IGroupDAOImpl implements IGroupDAO{

    public void add(Group group) {
        SqlSession session = DBUtil.getSqlSessionFactory().openSession();
        try{
            IGroupDAO dao = session.getMapper(IGroupDAO.class);
            dao.add(group);
            session.commit();
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
    }

    public void deleteById(int id) {
        SqlSession session = DBUtil.getSqlSessionFactory().openSession();
        try{
            IGroupDAO dao = session.getMapper(IGroupDAO.class);
            dao.deleteById(id);
            session.commit();
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }

    }

    public Group getById(int id) {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();

        Group group = null;
        try{
            IGroupDAO dao = session.getMapper(IGroupDAO.class);
            group = dao.getById(id);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return group;
    }

    public Group getByIdResultMap(int id) {
        SqlSessionFactory sqlSessionFactory = DBUtil.getSqlSessionFactory();
        SqlSession session = sqlSessionFactory.openSession();
        Group group = null;
        try{
            IGroupDAO dao = session.getMapper(IGroupDAO.class);
            group = dao.getByIdResultMap(id);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            session.close();
        }
        return group;
    }

    public void update(Group group) {
        // TODO Auto-generated method stub

    }


    public static void main(String[] args) {
        //System.out.println(new IGroupDAOImpl().getByIdResultMap(1));

        /*Group group = new Group();
        group.setId(3);
        group.setName("南京农业2");
        group.setPosition("南京信新街口2");
        new IGroupDAOImpl().add(group);*/

        Group group = new IGroupDAOImpl().getById(1);

        for(Student s:group.getStudents()){
            System.out.println(s.getId()+" , " + s.getName());
        }

    }
}

至此，对于一个初学者来说，需要了解的知识，上面的内容都有所概括，关键是灵活的应用。看的时候注意结合，如Student.xml       ，然后IStudentDAO.java， 最后看实现IStudentDAOImpl.java