Mybatis学习

公告

Posted on 2018-08-02 16:06 _wahaha 阅读(89) 评论(0) 收藏举报

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">

insert into students(id,name,sal) values(1,'哈哈',7000)

</insert>

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">

</dataSource>

</environment>

</environments>

</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">

insert into students(id,name,sal) values(1,'哈哈',7000)

</insert>

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">

</dataSource>

</environment>

</environments>

</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">

insert into students(id,name,sal) values(#{id},#{name},#{sal})

</insert>

update students set name=#{name},sal=#{sal} where id=#{id}

</update>

select id,name,sal from students where id=#{anything}

</select>

select id,name,sal from students

</select>

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">

insert into students(id,name,sal) values(#{id},#{name},#{sal})

</insert>

select id,name,sal from students limit #{pstart},#{psize}

</select>

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">

select id,name,sal from students

<where>

and name=#{pname}

</if>

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">

update students

<set>

name=#{name},

</if>

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">

delete from students where id in

<!--

${ids}

</foreach>

-->

${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">

id,

</if>

name,

</if>

sal,

</if>

</trim>

</sql>

#{id},

</if>

#{name},

</if>

#{sal},

</if>

</trim>

</sql>

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】

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