Mybatis

mybatis：注意点

1：关联查询的时候在被动方必须写别名，

2：limit 分页必须￥{} 美元符号

3：在bean里面必须描述关联关系,说白了就是在一方bean里面写list<Obj> 或者在多方bean中写Obj obj属性并生成setter，getter方法

4：通过Bean的setter getter 方法设值值或者取值，必须注意：必须要和数据库字段保持一致，否则就必须写写别名或者在property中映射

===============================================================================================

select

stu_id as stuId,

stu_name as stuName,

stu_class as stuClass

from student

</select>

一、返回值类型：1、返回Bean的情况下如果数据库表的字段于bean对象属性不一致的时候必须设置两者保持一致

2、返回java.util.Map之类的东西时，只要却包数据库字段正确就OK

二、

< typeAliases>

</ typeAliases>

凡是用到用到比如：com.shubiao.mybatis.bean.User 的时候都用类名代替

三、

<transactionManager type ="MANAGED"/> <!-- MANAGED/JDBC:注如果使用MANAGED,则无需关心事物提交和关闭的情况

如果使用JDBC的话需要手动提交事物，和关闭连接，否则它会一直被占用 -->

四、

< mappers>

</ mappers>

五、

select userId,userUsername,userPassword,user_email as userEmail from user where userId=#{userId}

</select>

<!-- useGeneratedKeys="true"

keyProperty="id"

以上参数的作用：如果有需求需要返回id的时候，并且表里面也是自动增长的情况下，保存数据需要设置这两个属性 -->

<insert id= "saveUser" parameterType ="User" useGeneratedKeys="true"

keyProperty="id">

insert into user (

userUsername,

userPassword,

userEmail)

values(

#{userUsername},

#{userPassword},

#{userEmail})

</insert>

六、在不想影响Bean的情况下可以建一个Params参数类来解决参数注入的问题

select userId,userUsername,userPassword,user_email as userEmail from user where userUsername like '%${userUsername}%'

and userPassword=#{userPassword} order by ${userId}

</select>

select userId,userUsername,userPassword,user_email as userEmail from user where userUsername like '%${userUsername}%'

and userPassword=#{userPassword} order by ${userId}

</select>

select count(0) from user;

</select>

第一步：导入数据库的驱动包和

mybatis-3.3.0-SNAPSHOT.jar

mybatis-spring-1.2.1.jar

第二步：

<?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">

</settings>

</typeAliases>

</transactionManager>

</dataSource>

</environment>

</environments>

</mappers>

</configuration>

第三步：

/**

* tzdesk系统平台

* mybatis

* com.tz.bean

* User.java

* 创建人:xuchengfei

* 时间：2015年11月18日-下午10:13:38

package com.tz.bean;

import java.util.Date;

/**

* User 创建人:xuchengfei 时间：2015年11月18日-下午10:13:38

* @version 1.0.0

public class User {

/* 主键 */

private Integer id;

// 用户名

private String username;

// 密码

private String password;

// 账号

private String account;

// 手机

private String telephone;

// 身份证

private String idcard;

// 性别：0女1男

private Integer male;

// 生日

private Date birthday;

// 邮箱

private String email;

// 地址

private String address;

// 年龄

private Integer age;

// 创建时间

private Date createTime;

// 删除状态0未删除1删除

private Integer isDelete;

// 更新时间

private Date updateTime;

// 报名老师

private Integer teacherId;

// 学科ID

private Integer subjectId;

// 状态 0未发布1发布

private Integer status;

// 1老师2学生

private Integer type;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getUsername() {

return username;

}

public void setUsername(String username) {

this.username = username;

}

public String getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

public String getAccount() {

return account;

}

public void setAccount(String account) {

this.account = account;

}

public String getTelephone() {

return telephone;

}

public void setTelephone(String telephone) {

this.telephone = telephone;

}

public String getIdcard() {

return idcard;

}

public void setIdcard(String idcard) {

this.idcard = idcard;

}

public Integer getMale() {

return male;

}

public void setMale(Integer male) {

this.male = male;

}

public Date getBirthday() {

return birthday;

}

public void setBirthday(Date birthday) {

this.birthday = birthday;

}

public String getEmail() {

return email;

}

public void setEmail(String email) {

this.email = email;

}

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

public Date getCreateTime() {

return createTime;

}

public void setCreateTime(Date createTime) {

this.createTime = createTime;

}

public Integer getIsDelete() {

return isDelete;

}

public void setIsDelete(Integer isDelete) {

this.isDelete = isDelete;

}

public Date getUpdateTime() {

return updateTime;

}

public void setUpdateTime(Date updateTime) {

this.updateTime = updateTime;

}

public Integer getTeacherId() {

return teacherId;

}

public void setTeacherId(Integer teacherId) {

this.teacherId = teacherId;

}

public Integer getSubjectId() {

return subjectId;

}

public void setSubjectId(Integer subjectId) {

this.subjectId = subjectId;

}

public Integer getStatus() {

return status;

}

public void setStatus(Integer status) {

this.status = status;

}

public Integer getType() {

return type;

}

public void setType(Integer type) {

this.type = type;

}

第四步：建立一个bean对应的sql配置文件 UserMapper.xml,定义增删查改

<?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,username,password FROM tz_user

</select>

INSERT tz_user(

username,

password,

account,

telephone,

idcard,

is_delete,

male,

birthday,

email,

address,

teacher_id,

subject_id,

age,

status,

type

)VALUES(

#{username},

#{password},

#{account},

#{telephone},

#{idcard},

#{isDelete},

#{male},

#{birthday},

#{email},

#{address},

#{teacherId},

#{subjectId},

#{age},

#{status},

#{type}

)

</insert>

UPDATE tz_user SET username = #{username} WHERE id = #{id}

</update>

delete from tz_user where id = #{id}

</delete>

delete from tz_user where username=#{username} and account=#{account}

</delete>

</mapper>

第五步：定义测试类:

/**

* tzdesk系统平台

* mybatis

* com.test.mybatis

* TestMyatisSessionFactory.java

* 创建人:xuchengfei

* 时间：2015年11月18日-下午10:02:51

package com.test.mybatis;

import java.io.IOException;

import java.io.InputStream;

import java.util.Date;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import org.junit.Before;

import org.junit.Test;

import com.tz.bean.User;

/**

* TestMyatisSessionFactory

* 创建人:xuchengfei

* 时间：2015年11月18日-下午10:02:51

* @version 1.0.0

public class TestMyatisSessionFactory {

private SqlSessionFactory sessionFactory;

@Before

public void before() throws IOException{

String resource = "mybatis-config.xml";

InputStream inputStream = Resources.getResourceAsStream(resource);

sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

}

@Test

public void handler() throws IOException{

SqlSession session = sessionFactory.openSession();

List<User> users = session.selectList("com.tz.bean.userMapper.findUsers");

for (User user : users) {

System.out.println("==============="+user.getUsername());

}

@Test

public void saveUser(){

SqlSession session = sessionFactory.openSession();

User user = new User();

user.setUsername("keke");

user.setPassword("111111");

user.setAccount("keke");

user.setTelephone("23423423423423");

user.setIdcard("324565543");

user.setIsDelete(0);

user.setMale(1);

user.setBirthday(new Date());

user.setEmail("2346546@qq.com");

user.setAddress("是打发是打发大");

user.setTeacherId(1);

user.setSubjectId(1);

user.setAge(30);

user.setStatus(1);

user.setType(2);

int count =session.insert("com.tz.bean.userMapper.saveUser", user);

System.out.println(count>0?"保存成功":"保存失败");

//session.close();

}

@Test

public void updateUser(){

SqlSession session = sessionFactory.openSession();

User user = new User();

user.setId(1);

user.setUsername("柯柯");

int count =session.insert("com.tz.bean.userMapper.updateUser", user);

System.out.println(count>0?"更新成功":"更新失败");

//session.close();

}

@Test

public void deleteUser(){

SqlSession session = sessionFactory.openSession();

// int count =session.delete("com.tz.bean.userMapper.deleteUser", 13);

// System.out.println(count>0?"删除成功":"删除失败");

// User user = new User();

// user.setId(14);

// int count =session.delete("com.tz.bean.userMapper.deleteUser", user);

// System.out.println(count>0?"删除成功":"删除失败");

//session.close();

Map<String, Object> map = new HashMap<String, Object>();

map.put("username","keke");

map.put("account", "keke");

int count = session.delete("com.tz.bean.userMapper.deleteUser2", map);

System.out.println(count>0?"删除成功":"删除失败");

}

注意点：

mybatis它是一个半面向对象orm框架，让我们重新回归sql最本真的写法。通过一个配置文件。去定义数据的连接的

相关信息，比如事件，插件，配置装载，事务的自动提交，缓存，数据类型处理等。通过解析配置装载到SqlsessionFactory

进行初始化，然后通过sqlsessionFactory获取会话对象SqlSession,获取连接对象，通过sqlSession中定义的api方法

和Mapper对象进行关联处理数据中增，删，查，改。比如

//查询单个实体

T session.selectOne(String mapperKey)

T session.selectOne(String mapperKey,Object params)

//查询返回多个实体

List<T> selectList(String mapperKey)

List<T> selectList(String mapperKey,Object params)

//保存方法

int insert(String mapperKey)

int insert(String mapperKey,Object params)

//修改方法

int update(String mapperKey)

int update(String mapperKey,Object params)

//删除方法

int delete(String mapperKey)

int delete(String mapperKey,Object params)

//返回map

Map<T,K> selectMap(String mapperKey)

Map<T,K> selectMap(String mapperKey,Object params)

mapperKey=是sql配置文件的命名空间+id

通过以后一些可以实现实现增删查改操作。如果你配置事务管理器是JDBC的话，在打开连接的时候，比如收到设置自动事务提交,sessionFactory.openSession(true)，如果

你设置的是 MANAGED,自动事务提交.

</transactionManager>