java深入探究16-mybatis
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1.引入mybatis
jsbc简单易学,上手快,非常灵活构建SQL,效率高但代码繁琐,难以写出高质量的代码
hibernate不用写SQL,完全以面向对象的方式设计和访问但处理复杂业务时,灵活度差
所以中间产物:mybatis就应运而生
2.mybatis说法和特定
1)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。
2)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)
3)jdbc/dbutils/springdao,hibernate/springorm,mybaits同属于ORM解决方案之一
3.mybatis快速入门
1)导入jar包(5个核心包+2个数据库访问包):asm-3.3.1.jar;cglib-2.2.2.jar;commons-logging-1.1.1.jar;log4j-1.2.16.jar;mybatis-3.1.1.jar;mysql-connector-java-5.1.7-bin.jar;ojdbc5.jar
2)创建sql:
--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) );
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; } }
3)配置映射文件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>
4)配置mybatis.xml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>
5)创建MyBatisUtil工具类
/** * 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"); } }
6)创建StudentDao
/** * 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)); } }
4. mybatis工作流程
1)通过Reader对象读取src目录下的mybatis.xml配置文件(改文件的名字和位置可变)
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,mybatis中默认
5)通过sqlSession对象读取StudentMapper.xml映射文件中操作编号,从而读取sql语句
6)事务提交必写
7)关闭SqlSession对象并且分离当前线程与sqlSession对象,让GC尽早回收
5.mybatis配置文件解析
1)StudentMapper.xml文件,提倡放在与实体同目录下,文件名任意
2)environments连接环境信息优化:
1.建一个db.properties用来存放连接信息
2.在mybatis中properties属性可以加载这个配置信息
3.连接环境配置属性值就可以用${mysql.url}形式从配置文件中获取了
3)StudentMapper.xml中insert标签parameterType="app04.Student"每次要类全路径
简化方式:
1.mybatis中添加
<!-- 设置类型别名 -->
<typeAliases>
<typeAlias type="app04.Student" alias="student"/>
</typeAliases>
2.之后在StudentMapper.xml中写类型时都可以用简称student了
<?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.mybatis映射文件祥解(StudentMapper.xml)
StudentMapper:存放表映射;sql语句
mybatis:连接环境信息,加载映射文件
7.基于MybatisUtil工具类,完成CURD操作
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="app09.Student"> <resultMap type="app09.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <!-- 增加学生 --> <insert id="add" parameterType="app09.Student"> insert into students(id,name,sal) values(#{id},#{name},#{sal}) </insert> <!-- 根据ID查询学生 如果参数不是一个实体的话,只是一个普通变量,例如:int,double,String 这里的#{中间的变量名可以随便写},不过提倡就用方法的形参 --> <select id="findById" parameterType="int" resultType="app09.Student"> select * from students where id=#{id} </select> <!-- 查询所有学生 理论上resultType要写List<Student> 但这里只需书写List中的类型即可,即只需书写Student的全路径名 --> <select id="findAll" resultType="app09.Student"> select id,name,sal from students </select> <!-- 更新学生 --> <update id="update" parameterType="app09.Student"> update students set name=#{name},sal=#{sal} where id=#{id} </update> <!-- 删除学生 --> <delete id="delete" parameterType="app09.Student"> delete form students where id=#{id} </delete> <!-- 注意:这个insert/update/delete标签只是一个模板,在做操作时,其实是以SQL语句为核心的 即在做增/删/时,insert/update/delete标签可通用, 但做查询时只能用select标签 我们提倡什么操作就用什么标签 --> </mapper>
StudentDao.java
package app09; import java.util.List; import org.apache.ibatis.session.SqlSession; import util.MybatisUtil; public class StudentDao { /** * 增加学生 */ public void add(Student student)throws Exception{ SqlSession sqlSession=null; try{ sqlSession=MybatisUtil.getSqlSession(); //开始事务 sqlSession.insert(Student.class.getName()+".add",student); sqlSession.commit(); //提交 }catch (Exception e) { e.printStackTrace(); sqlSession.rollback(); }finally{ //解除关系让GC处理sqlSession对象 MybatisUtil.closeSqlSession(); } } /** *根据ID 查询学生 */ public Student findById(int id)throws Exception{ SqlSession sqlSession=null; try{ sqlSession=MybatisUtil.getSqlSession(); //开始事务 Student student=sqlSession.selectOne(Student.class.getName()+".findById", id); sqlSession.commit(); return student; //提交 }catch (Exception e) { e.printStackTrace(); sqlSession.rollback(); throw new RuntimeException(); }finally{ //解除关系让GC处理sqlSession对象 MybatisUtil.closeSqlSession(); } } /** * 查询所有学生 */ public List<Student> findAll()throws Exception{ SqlSession sqlSession=null; try{ sqlSession=MybatisUtil.getSqlSession(); //开始事务 return sqlSession.selectOne(Student.class.getName()+".findAll"); //提交 }catch (Exception e) { e.printStackTrace(); sqlSession.rollback(); throw new RuntimeException(); }finally{ //解除关系让GC处理sqlSession对象 MybatisUtil.closeSqlSession(); } } /** * 更新学生 */ public void update(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.update(Student.class.getName()+".update",student); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } /** * 删除学生 */ public void delete(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.delete(Student.class.getName()+".delete",student); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); //dao.add(new Student(1,"哈哈",7000D)); //dao.add(new Student(2,"呵呵",8000D)); //dao.add(new Student(3,"班长",9000D)); //dao.add(new Student(4,"键状高",10000D)); //Student student = dao.findById(4); //List<Student> studentList = dao.findAll(); //for(Student student : studentList){ // System.out.print(student.getId()+":"+student.getName()+":"+student.getSal()); // System.out.println(); //} Student student = dao.findById(3); System.out.println(student.getName()); //student.setName("靓班长"); //dao.update(student); //Student student = dao.findById(3); //System.out.print(student.getId()+":"+student.getName()+":"+student.getSal()); //dao.delete(student); } }
8.分页查询
package app10; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import org.apache.ibatis.session.SqlSession; import util.MybatisUtil; public class StudentDao { public void add(Student student)throws Exception{ SqlSession sqlSession=null; try{ sqlSession.insert(Student.class.getName()+".add",student); sqlSession.commit(); }catch (Exception e) { e.printStackTrace(); sqlSession.rollback(); }finally{ MybatisUtil.closeSqlSession(); } } /** * 分页 * 在映射文件中参数不能是多个,对个多个参数需要封装用map * @param start * @param size * @return */ public List<Student> findAllWithFy(int start,int size){ SqlSession sqlSession=null; try{ sqlSession = MybatisUtil.getSqlSession(); Map<String,Object> map = new LinkedHashMap<String,Object>(); map.put("pstart",start); map.put("psize",size); return sqlSession.selectList(Student.class.getName()+".findAllWithFy", map); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw new RuntimeException(); }finally{ MybatisUtil.closeSqlSession(); } } /** * 分页有条件 * 在映射文件中参数不能是多个,对个多个参数需要封装用map * @param start * @param size * @return */ public List<Student> findAllWithFy(String name,int start,int size){ SqlSession sqlSession=null; try{ sqlSession = MybatisUtil.getSqlSession(); Map<String,Object> map = new LinkedHashMap<String,Object>(); map.put("pstart",start); map.put("psize",size); map.put("pname", "%"+name+"%"); return sqlSession.selectList(Student.class.getName()+".findAllByNameWithFy", map); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw new RuntimeException(); }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); //for(int i=1;i<=10;i++){ // dao.add(new Student(i,"哈哈",7000D)); //} System.out.println("--------------------第一页"); List<Student> studentList1=dao.findAllWithFy("xiao",0, 2); //List<Student> studentList1 = dao.findAllByNameWithFy("哈",0,3); for(Student s : studentList1){ System.out.println(s.getId()+":"+s.getName()+":"+s.getSal()); } //System.out.println("--------------------第二页"); //List<Student> studentList2 = dao.findAllByNameWithFy("哈",3,3); //for(Student s : studentList2){ // System.out.println(s.getId()+":"+s.getName()+":"+s.getSal()); //} //System.out.println("--------------------第三页"); //List<Student> studentList3 = dao.findAllByNameWithFy("哈",6,3); //for(Student s : studentList3){ // System.out.println(s.getId()+":"+s.getName()+":"+s.getSal()); //} } }
<?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="app10.Student"> <resultMap type="app10.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <insert id="add" parameterType="app10.Student"> insert into students(id,name,sal) values(#{id},#{name},#{sal}) </insert> <select id="findAllWithFy" parameterType="map" resultMap="studentMap"> select id,name,sal from students limit #{pstart},#{psize} </select> <select id="findAllByNameWithFy" parameterType="map" resultMap="studentMap"> select id,name,sal from students where name like #{pname} limit #{pstart},#{psize} </select> </mapper>
9。动态SQL操作
1)动态查询:select id,name,sal from students where 1=1 and name=? and sal=?
<where> <if test="pid!=null"> and id=#{pid} </if> <if test="pname!=null"> and name=#{pname} </if> <if test="psal=null"> and sal=#{psal} </if> </where>
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="app11.Student"> <resultMap type="app11.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <select id="findAll" parameterType="map" resultMap="studentMap"> select * from students <where> <if test="pid!=null"> and id=#{pid} </if> <if test="pname!=null"> and name=#{pname} </if> <if test="psal=null"> and sal=#{psal} </if> </where> </select> </mapper>
StudentDao.java
package app11; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import org.apache.ibatis.session.SqlSession; import util.MybatisUtil; /** * 持久层 * @author AdminTC */ public class StudentDao { /** * 有条件的查询所有学生 */ public List<Student> findAll(Integer id,String name,Double sal) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); Map<String,Object> map = new LinkedHashMap<String,Object>(); map.put("pid",id); map.put("pname",name); map.put("psal",sal); return sqlSession.selectList(Student.class.getName()+".findAll",map); }catch(Exception e){ e.printStackTrace(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); List<Student> studentList = dao.findAll(4,null,null); for(Student s : studentList){ System.out.println(s.getId()+":"+s.getName()+":"+s.getSal()); } } }
2)动态更新:update students set name=?,sal=? where id=?
StudentDao.java
package app12; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import org.apache.ibatis.session.SqlSession; import util.MybatisUtil; /** * 持久层 * @author AdminTC */ public class StudentDao { /** * 有条件更新学生 */ public void dynaUpdate(Integer id,String name,Double sal) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); Map<String,Object> map = new HashMap<String, Object>(); map.put("pid",id); map.put("pname",name); map.put("psal",sal); sqlSession.update("studentNamespace.dynaUpdate",map); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); //关注SQL的变化 //dao.dynaUpdate(1,null,9000D);//update students set sal=? where id=? //dao.dynaUpdate(1,"笨笨",null);//update students set name=? where id=? dao.dynaUpdate(1,"笨笨",10000D);//update students set name=? and sal=? where id=? } }
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="studentNamespace"> <resultMap type="app12.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <!-- set标签自动判断哪个是最后一个字段,会自动去掉最后一个,号 --> <update id="dynaUpdate" parameterType="map"> update students <set> <if test="pname!=null"> students_name = #{pname}, </if> <if test="psal!=null"> students_sal = #{psal}, </if> </set> where students_id = #{pid} </update> </mapper>
3)动态删除
delete from students where id in (1,3,5,7)
select id,name,sal from students where id in (2,4,6,8)
StudentDao.java
package app13; import java.util.ArrayList; import java.util.List; import org.apache.ibatis.session.SqlSession; import app13.StudentDao; import util.MybatisUtil; /** * 持久层 * @author AdminTC */ public class StudentDao { /** * 根据ID批量删除学生(数组版本) * @param ids * @throws Exception */ public void dynaDeleteArray(int ...ids)throws Exception{ SqlSession sqlSession=null; try{ sqlSession=MybatisUtil.getSqlSession(); sqlSession.delete(Student.class.getName()+".dynaDeleteArray",ids); sqlSession.commit(); }catch (Exception e) { e.printStackTrace(); sqlSession.rollback(); throw new RuntimeException(); }finally{ MybatisUtil.closeSqlSession(); } } public void dynaDeleteList(List<Integer> ids)throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.delete("studentNamespace.dynaDeleteList",ids); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); dao.dynaDeleteArray(2,4); //List<Integer> ids = new ArrayList<Integer>(); //ids.add(6); //ids.add(8); //ids.add(9); //dao.dynaDeleteList(ids); } }
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="app13.Student"> <resultMap type="app13.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <delete id="dynaDeleteArray"> delete from students where id in <!-- foreach用于迭代数组元素 open表示开始符号 close表示结束符合 separator表示元素间的分隔符 item表示迭代的数组,属性值可以任意,但提倡与方法的数组名相同 #{ids}表示数组中的每个元素值 --> <foreach collection="array" open="(" close=")" separator="," item="ids"> #{ids} </foreach> </delete> <delete id="dynaDeleteList"> delete from students where id in <foreach collection="list" open="(" close=")" separator="," item="ids"> #{ids} </foreach> </delete> </mapper>
4)动态插入:insert into student(id,name,sal) values(?,?,?)
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="studentNamespace"> <resultMap type="app14.Student" id="studentMap"> <id property="id" column="id"/> <result property="name" column="name"/> <result property="sal" column="sal"/> </resultMap> <!-- 定义sql片段 字段名,id属性值任意写--> <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> <!-- 定义sql片段 ? --> <sql id="value"> <!-- 去掉最后一个, --> <trim suffixOverrides=","> <if test="id!=null"> #{}, </if> <if test="name!=null"> #{}, </if> <if test="sal!=null"> #{}, </if> </trim> </sql> <insert id="dynaInsert" parameterType="day14.Student"> insert into students(<include refid="key"></include>) values(<include refid="value"></include>) </insert> </mapper>
StudentDao.java
package app14; import java.util.ArrayList; import java.util.List; import org.apache.ibatis.session.SqlSession; import app13.Student; import util.MybatisUtil; /** * 持久层 * @author AdminTC */ public class StudentDao { /** * 动态插入学生 */ public void dynaInsert(Student student) throws Exception{ SqlSession sqlSession = null; try{ sqlSession = MybatisUtil.getSqlSession(); sqlSession.insert("studentNamespace.dynaInsert",student); sqlSession.commit(); }catch(Exception e){ e.printStackTrace(); sqlSession.rollback(); throw e; }finally{ //MybatisUtil.closeSqlSession(); } } public static void main(String[] args) throws Exception{ StudentDao dao = new StudentDao(); //dao.dynaInsert(new Student(1,"哈哈",7000D));//insert into 表名(*,*,*) values(?,?,?) dao.dynaInsert(new Student(2,"哈哈",null));//insert into 表名(*,*) values(?,?) //dao.dynaInsert(new Student(3,null,7000D));//insert into 表名(*,*) values(?,?) //dao.dynaInsert(new Student(4,null,null));//insert into 表名(*) values(?) } }
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