32mybatis

Posted 2020-08-19 梦之魂_JG

第一章回顾jdbc开发

1）优点：简单易学,上手快,非常灵活构建SQL，效率高

2）缺点：代码繁琐，难以写出高质量的代码（例如：资源的释放，SQL注入安全性等）

开发者既要写业务逻辑，又要写对象的创建和销毁，必须管底层具体数据库的语法

（例如：分页）。

3）适合于超大批量数据的操作，速度快

 

 

第二章回顾hibernate单表开发

1）优点：不用写SQL，完全以面向对象的方式设计和访问，不用管底层具体数据库的语法，（例如：分页）便于理解。

2）缺点：处理复杂业务时，灵活度差, 复杂的HQL难写难理解，例如多表查询的HQL语句

3）适合于中小批量数据的操作，速度慢

 

 

第三章什么是mybatis，mybatis有什么特点

1）基于上述二种支持，我们需要在中间找到一个平衡点呢？结合它们的优点，摒弃它们的缺点，

这就是myBatis，现今myBatis被广泛的企业所采用。

2）MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。

3）iBATIS一词来源于“internet”和“abatis”的组合，是一个基于Java的持久层框架。iBATIS提供的持久层框架包括SQL Maps和Data Access Objects（DAO）

4）jdbc/dbutils/springdao，hibernate/springorm，mybaits同属于ORM解决方案之一

 

 

第四章 mybatis快速入门

1）创建一个mybatis-day01这么一个javaweb工程或java工程

2）导入mybatis和mysql/oracle的jar包到/WEB-INF/lib目录下

3）创建students.sql表

--mysql语法 create table students(    id  int(5) primary key,    name varchar(10),    sal double(8,2) ); --oracle语法 create table students(    id  number(5) primary key,    name varchar2(10),    sal number(8,2) );

4）创建Student.java

/**  * 学生  * @author AdminTC  */ public class Student {     private Integer id;     private String name;     private Double sal;     public Student(){}     public Integer getId() {        return id;     }     public void setId(Integer id) {        this.id = id;     }     public String getName() {        return name;     }     public void setName(String name) {        this.name = name;     }     public Double getSal() {        return sal;     }     public void setSal(Double sal) {        this.sal = sal;     } }

5）在entity目录下创建StudentMapper.xml配置文件

<?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="mynamespace">     <insert id="add1">        insert into students(id,name,sal) values(1,‘哈哈‘,7000)     </insert>     <insert id="add2" parameterType="cn.itcast.javaee.mybatis.app05.Student">        insert into students(id,name,sal) values(#{id},#{name},#{sal})     </insert> </mapper>

6）在src目录下创建mybatis.xml配置文件

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">   <configuration>     <environments default="development">        <environment id="development">            <transactionManager type="JDBC"/>            <dataSource type="POOLED">               <property name="driver" value="com.mysql.jdbc.Driver"/>               <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"/>               <property name="username" value="root"/>                <property name="password" value="root"/>             </dataSource>        </environment>        </environments>     <mappers>        <mapper resource="cn/itcast/javaee/mybatis/app05/StudentMapper.xml"/>     </mappers> </configuration>

7）在util目录下创建MyBatisUtil.java类，并测试与数据库是否能连接

/**  * MyBatis工具类  * @author AdminTC  */ public class MyBatisUtil {     private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();     private static SqlSessionFactory sqlSessionFactory;     static{        try {            Reader reader = Resources.getResourceAsReader("mybatis.xml");            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);        } catch (IOException e) {            e.printStackTrace();            throw new RuntimeException(e);        }     }     private MyBatisUtil(){}     public static SqlSession getSqlSession(){        SqlSession sqlSession = threadLocal.get();        if(sqlSession == null){            sqlSession = sqlSessionFactory.openSession();            threadLocal.set(sqlSession);        }        return sqlSession;     }     public static void closeSqlSession(){        SqlSession sqlSession = threadLocal.get();        if(sqlSession != null){            sqlSession.close();            threadLocal.remove();        }     }     public static void main(String[] args) {        Connection conn = MyBatisUtil.getSqlSession().getConnection();        System.out.println(conn!=null?"连接成功":"连接失败");     } }

8）在dao目录下创建StudentDao.java类并测试

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 增加学生（无参）      */     public void add1() throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.insert("mynamespace.add1");        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();        }        MyBatisUtil.closeSqlSession();     }     /**      * 增加学生（有参）      */     public void add2(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.insert("mynamespace.add2",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();        }        MyBatisUtil.closeSqlSession();     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();        dao.add1();        dao.add2(new Student(2,"呵呵",8000D));     } }

 

 

第五章 mybatis工作流程

1）通过Reader对象读取src目录下的mybatis.xml配置文件(该文本的位置和名字可任意)

2）通过SqlSessionFactoryBuilder对象创建SqlSessionFactory对象

3）从当前线程中获取SqlSession对象

4）事务开始，在mybatis中默认

5）通过SqlSession对象读取StudentMapper.xml映射文件中的操作编号，从而读取sql语句

6）事务提交，必写

7）关闭SqlSession对象，并且分开当前线程与SqlSession对象，让GC尽早回收

 

 

第六章 mybatis配置文件祥解（mybatis.xml）

1）以下是StudentMapper.xml文件，提倡放在与实体同目录下，文件名任意

<?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="mynamespace">     <insert id="add1">        insert into students(id,name,sal) values(1,‘哈哈‘,7000)     </insert>     <insert id="add2" parameterType="cn.itcast.javaee.mybatis.app05.Student">        insert into students(id,name,sal) values(#{id},#{name},#{sal})     </insert> </mapper>

 

 

第七章 mybatis映射文件祥解(StudentMapper.xml)

1）以下是mybatis.xml文件，提倡放在src目录下，文件名任意

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">   <configuration>     <environments default="development">        <environment id="development">            <transactionManager type="JDBC"/>            <dataSource type="POOLED">               <property name="driver" value="com.mysql.jdbc.Driver"/>               <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"/>               <property name="username" value="root"/>                <property name="password" value="root"/>             </dataSource>        </environment>        </environments>     <mappers>        <mapper resource="cn/itcast/javaee/mybatis/app05/StudentMapper.xml"/>     </mappers> </configuration>

 

 

第八章MybatisUtil工具类的作用

1）在静态初始化块中加载mybatis配置文件和StudentMapper.xml文件一次

2）使用ThreadLocal对象让当前线程与SqlSession对象绑定在一起

3）获取当前线程中的SqlSession对象，如果没有的话，从SqlSessionFactory对象中获取SqlSession对象

4）获取当前线程中的SqlSession对象，再将其关闭，释放其占用的资源

/**  * MyBatis工具类  * @author AdminTC  */ public class MyBatisUtil {     private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();     private static SqlSessionFactory sqlSessionFactory;     static{        try {            Reader reader = Resources.getResourceAsReader("mybatis.xml");            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);        } catch (IOException e) {            e.printStackTrace();            throw new RuntimeException(e);        }     }     private MyBatisUtil(){}     public static SqlSession getSqlSession(){        SqlSession sqlSession = threadLocal.get();        if(sqlSession == null){            sqlSession = sqlSessionFactory.openSession();            threadLocal.set(sqlSession);        }        return sqlSession;     }     public static void closeSqlSession(){        SqlSession sqlSession = threadLocal.get();        if(sqlSession != null){            sqlSession.close();            threadLocal.remove();        }     }     public static void main(String[] args) {        Connection conn = MyBatisUtil.getSqlSession().getConnection();        System.out.println(conn!=null?"连接成功":"连接失败");     } }

 

 

第九章基于MybatisUtil工具类，完成CURD操作

1）StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 增加学生      */     public void add(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.insert("mynamespace.add",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 修改学生      */     public void update(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.update("mynamespace.update",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 查询单个学生      */     public Student findById(int id) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            Student student = sqlSession.selectOne("mynamespace.findById",id);            return student;        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 查询多个学生      */     public List<Student> findAll() throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            return sqlSession.selectList("mynamespace.findAll");        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 删除学生      */     public void delete(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.delete("mynamespace.delete",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }

2）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="mynamespace">     <insert id="add" parameterType="cn.itcast.javaee.mybatis.app09.Student">        insert into students(id,name,sal) values(#{id},#{name},#{sal})     </insert>     <update id="update" parameterType="cn.itcast.javaee.mybatis.app09.Student">        update students set name=#{name},sal=#{sal} where id=#{id}     </update>     <select id="findById" parameterType="int" resultType="cn.itcast.javaee.mybatis.app09.Student">        select id,name,sal from students where id=#{anything}     </select>     <select id="findAll" resultType="cn.itcast.javaee.mybatis.app09.Student">        select id,name,sal from students     </select>     <delete id="delete" parameterType="cn.itcast.javaee.mybatis.app09.Student">        delete from students where id=#{id}     </delete> </mapper>

 

 

第十章分页查询

1）StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 增加学生      */     public void add(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.insert("mynamespace.add",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 无条件分页查询学生      */     public List<Student> findAllWithFy(int start,int size) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            Map<String,Integer> map = new LinkedHashMap<String,Integer>();            map.put("pstart",start);            map.put("psize",size);            return sqlSession.selectList("mynamespace.findAllWithFy",map);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     /**      * 有条件分页查询学生      */     public List<Student> findAllByNameWithFy(String name,int start,int size) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            Map<String,Object> map = new LinkedHashMap<String,Object>();            map.put("pname","%"+name+"%");            map.put("pstart",start);            map.put("psize",size);            return sqlSession.selectList("mynamespace.findAllByNameWithFy",map);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();        System.out.println("-----------Page1");        for(Student s:dao.findAllByNameWithFy("哈",0,3)){            System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());        }        System.out.println("-----------Page2");        for(Student s:dao.findAllByNameWithFy("哈",3,3)){            System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());        }        System.out.println("-----------Page3");        for(Student s:dao.findAllByNameWithFy("哈",6,3)){            System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());        }        System.out.println("-----------Page4");        for(Student s:dao.findAllByNameWithFy("哈",9,3)){            System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());        }     } }

2）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="mynamespace">     <insert id="add" parameterType="cn.itcast.javaee.mybatis.app10.Student">        insert into students(id,name,sal) values(#{id},#{name},#{sal})     </insert>     <select id="findAllWithFy" parameterType="map" resultType="cn.itcast.javaee.mybatis.app10.Student">        select id,name,sal from students limit #{pstart},#{psize}     </select>     <select id="findAllByNameWithFy" parameterType="map" resultType="cn.itcast.javaee.mybatis.app10.Student">        select id,name,sal from students where name like #{pname} limit #{pstart},#{psize}     </select> </mapper>

   思考：oracle分页如何做呢？

 

 

第十一章动态SQL操作之查询

1）  查询条件不确定，需要根据情况产生SQL语法，这种情况叫动态SQL

2）  参见<<动态SQL—查询.JPG>>

StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 动态SQL--查询      */     public List<Student> dynaSQLwithSelect(String name,Double sal) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            Map<String,Object> map = new LinkedHashMap<String, Object>();            map.put("pname",name);            map.put("psal",sal);            return sqlSession.selectList("mynamespace.dynaSQLwithSelect",map);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();               List<Student> studentList1 = dao.dynaSQLwithSelect("哈哈",null);        for(Student student : studentList1){            System.out.println(student.getId()+":"+student.getName()+":"+student.getSal());        }        System.out.println("--------------");        List<Student> studentList2 = dao.dynaSQLwithSelect(null,7000D);        for(Student student : studentList2){            System.out.println(student.getId()+":"+student.getName()+":"+student.getSal());        }        System.out.println("--------------");        List<Student> studentList3 = dao.dynaSQLwithSelect("哈哈",7000D);        for(Student student : studentList3){            System.out.println(student.getId()+":"+student.getName()+":"+student.getSal());        }        System.out.println("--------------");        List<Student> studentList4 = dao.dynaSQLwithSelect(null,null);        for(Student student : studentList4){            System.out.println(student.getId()+":"+student.getName()+":"+student.getSal());        }        System.out.println("--------------");     } }

    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="mynamespace">     <select id="dynaSQLwithSelect" parameterType="map" resultType="cn.itcast.javaee.mybatis.app11.Student">        select id,name,sal from students        <where>            <if test="pname!=null">               and name=#{pname}            </if>            <if test="psal!=null">               and sal=#{psal}            </if>        </where>       </select> </mapper>

 

   

第十二章动态SQL操作之更新

1）  更新条件不确定，需要根据情况产生SQL语法，这种情况叫动态SQL

2）  参见<<动态SQL—更新.JPG>>

StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 动态SQL--更新      */     public void dynaSQLwithUpdate(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.update("mynamespace.dynaSQLwithUpdate",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();        dao.dynaSQLwithUpdate(new Student(10,null,5000D));        dao.dynaSQLwithUpdate(new Student(10,"哈哈",null));        dao.dynaSQLwithUpdate(new Student(10,"哈哈",6000D));     } }

    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="mynamespace">     <update id="dynaSQLwithUpdate" parameterType="cn.itcast.javaee.mybatis.app12.Student">        update students        <set>            <if test="name!=null">               name=#{name},            </if>            <if test="sal!=null">               sal=#{sal},            </if>        </set>        where id=#{id}     </update>  </mapper>

 

 

第十三章动态SQL操作之删除

1）  根据ID删除学生

2）  参见<<动态SQL—删除.JPG>>

StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 动态SQL--删除      */     public void dynaSQLwithDelete(int... ids) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.delete("mynamespace.dynaSQLwithDelete",ids);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();        dao.dynaSQLwithDelete(1,3,5,7);     } }

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="mynamespace">     <!-- item表示迭代的参数 -->     <delete id="dynaSQLwithDelete">        delete from students where id in        <!--        <foreach collection="array" open="(" close=")" separator="," item="ids">            ${ids}        </foreach>        -->        <foreach collection="list" open="(" close=")" separator="," item="ids">            ${ids}        </foreach>     </delete>  </mapper>

 

 

第十四章动态SQL操作之插入

1）  根据条件，插入一个学生

2）参见<<动态SQL—插入.JPG>>

    StudentDao.java

/**  * 持久层  * @author AdminTC  */ public class StudentDao {     /**      * 动态SQL--插入      */     public void dynaSQLwithInsert(Student student) throws Exception{        SqlSession sqlSession = MyBatisUtil.getSqlSession();        try{            sqlSession.insert("mynamespace.dynaSQLwithInsert",student);        }catch(Exception e){            e.printStackTrace();            sqlSession.rollback();            throw e;        }finally{            sqlSession.commit();            MyBatisUtil.closeSqlSession();        }     }     public static void main(String[] args) throws Exception{        StudentDao dao = new StudentDao();        dao.dynaSQLwithInsert(new Student(1,"哈哈",7000D));        dao.dynaSQLwithInsert(new Student(2,"哈哈",null));        dao.dynaSQLwithInsert(new Student(3,null,7000D));     } }

    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="mynamespace">     <sql id="key">        <trim suffixOverrides=",">            <if test="id!=null">               id,            </if>            <if test="name!=null">               name,            </if>            <if test="sal!=null">               sal,            </if>        </trim>     </sql>     <sql id="value">        <trim suffixOverrides=",">            <if test="id!=null">               #{id},            </if>            <if test="name!=null">               #{name},            </if>            <if test="sal!=null">               #{sal},            </if>        </trim>     </sql>     <insert id="dynaSQLwithInsert" parameterType="cn.itcast.javaee.mybatis.app14.Student">        insert into students(<include refid="key"/>) values(<include refid="value"/>)     </insert> </mapper>

 

 

第十五章jsp/js/jquery/easyui/json + @springmvc + spring + mybatis + oracle开发

【员工管理系统--增加员工】