MyBatis开发及简介

来源：互联网发布：云南2016年旅游数据编辑：程序博客网时间：2024/06/05 05:33

一、开发代码结构图

二、配置文件简介：

1、jdbc.properties：

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/sampledb
jdbc.username=root
jdbc.password=root

2、mybatis-config.xml：

<?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>
<properties resource="jdbc.properties"/>

<typeAliases>
<package name="com.java.mybatis.model"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/java/mybatis/mappers/StudentMapper.xml" />
</mappers>
</configuration>

3、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="com.java.mybatis.mappers.StudentMapper">
<insert id="add" parameterType="Student" >
insert into t_student values(null,#{name},#{age})
</insert>
</mapper>

4、StudentMapper.java：

package com.java.mybatis.mappers;

import com.java.mybatis.model.Student;

public interface StudentMapper {

public int add(Student student);
}

使用注解的代码如下：

import java.util.List;import org.apache.ibatis.annotations.Delete;import org.apache.ibatis.annotations.Insert;import org.apache.ibatis.annotations.One;import org.apache.ibatis.annotations.Result;import org.apache.ibatis.annotations.Results;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.annotations.Update;import com.java.mybatis.model.Student;public interface StudentMapper {@Insert("insert into t_student values(null,#{name},#{age})")public int insertStudent(Student student);@Update("update t_student set name=#{name},age=#{age} where id=#{id}")public int updateStudent(Student student);@Delete("delete from t_student where id=#{id}")public int deleteStudent(int id);@Select("select * from t_student where id=#{id}")public Student getStudentById(Integer id);@Select("select * from t_student")@Results({@Result(id=true,column="id",property="id"),@Result(column="name",property="name"),@Result(column="age",property="age")})public List<Student> findStudents();@Select("select * from t_student where id=#{id}")@Results({@Result(id=true,column="id",property="id"),@Result(column="name",property="name"),@Result(column="age",property="age"),@Result(column="addressId",property="address",one=@One(select="com.java1234.mappers.AddressMapper.findById"))})public Student selectStudentWithAddress(int id);@Select("select * from t_student where gradeId=#{gradeId}")@Results({@Result(id=true,column="id",property="id"),@Result(column="name",property="name"),@Result(column="age",property="age"),@Result(column="addressId",property="address",one=@One(select="com.java1234.mappers.AddressMapper.findById"))})public Student selectStudentByGradeId(int gradeId);@Select("select * from t_student where id=#{id}")@Results({@Result(id=true,column="id",property="id"),@Result(column="name",property="name"),@Result(column="age",property="age"),@Result(column="addressId",property="address",one=@One(select="com.java1234.mappers.AddressMapper.findById")),@Result(column="gradeId",property="grade",one=@One(select="com.java1234.mappers.GradeMapper.findById"))})public Student selectStudentWithAddressAndGrade(int id);}

5、Student.java：

package com.java.mybatis.model;

public class Student {

private Integer id;

private String name;

private Integer age;

public Student() {

super();

}

public Student(String name, Integer age) {

super();

this.name = name;

this.age = age;

}

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 Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

6、SqlSessionFactoryUtil.java：

package com.java.mybatis.util;

import java.io.InputStream;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class SqlSessionFactoryUtil {

private static SqlSessionFactory sqlSessionFactory;

public static SqlSessionFactory getSqlSessionFactory(){

if(sqlSessionFactory==null){

InputStream inputStream=null;

try{ inputStream=Resources.getResourceAsStream("mybatis-config.xml");

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

}catch(Exception e){

e.printStackTrace();

}

return sqlSessionFactory;

}

public static SqlSession openSession(){

return getSqlSessionFactory().openSession();

}

7、StudentTest.java：

package com.java.mybatis.service;

import org.apache.ibatis.session.SqlSession;

import com.java.mybatis.mappers.StudentMapper;
import com.java.mybatis.model.Student;
import com.java.mybatis.util.SqlSessionFactoryUtil;

public class StudentTest {

public static void main(String[] args) {
SqlSession sqlSession=SqlSessionFactoryUtil.openSession();
StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);
Student student=new Student("张三",12);
int result=studentMapper.add(student);
sqlSession.commit();
if(result>0){
System.out.println("添加成功！");
}
}
}

environments：

MyBatis 支持多个环境，可以任意配置；

transactionManager

MyBatis 支持两种类型的事务管理器：JDBC 和MANAGED(托管)；

JDBC：应用程序负责管理数据库连接的生命周期；

MANAGED ：由应用服务器负责管理数据库连接的生命周期； ( 一般商业服务器才有此功能，如JBOSS,WebLogic)

dataSource

用来配置数据源；类型有：UNPOOLED，POOLED，JNDI；

UNPOOLED，没有连接池，每次数据库操作，MyBatis 都会创建一个新的连接，用完后，关闭；适合小并发项目；

POOLED，用上了连接池；

JNDI，使用应用服务器配置JNDI 数据源获取数据库连接；

properties

配置属性

typeAliases

给类的完成限定名取别名，方便使用；如下：

<typeAliases>
<package name="com.java.mybatis.model"/>
</typeAliases>

mappers

引入映射文件，例如mybatis-config.xml：

配置Log4j 日志

log4j.rootLogger=info,appender1,appender2
log4j.appender.appender1=org.apache.log4j.ConsoleAppender

log4j.appender.appender2=org.apache.log4j.FileAppender
log4j.appender.appender2.File=D:/logFile.txt

log4j.appender.appender1.layout=org.apache.log4j.TTCCLayout
log4j.appender.appender2.layout=org.apache.log4j.TTCCLayout

三、一对多关系、多对一关系

四、动态 SQL

1、if 条件

<select id="searchStudents" parameterType="Map" resultMap="StudentResult">

select * from t_student

where gradeId=#{gradeId}
<if test="name!=null">
and name like #{name}
</if>
<if test="age!=nulll">
and age=#{age}
</if>
</select>
2、choose，when和otherwise条件
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="addressId" column="id" select="com.java.mybatis.mappers.AddressMapper.findById"></association>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select t1.id,t1.age,t1.name,t1.addressId from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>

3、where条件

1，自动加上where；
2，如果where 子句以and 或者or 开头，则自动删除第一个and 或者or；

<select id="searchStudents3" parameterType="Map" resultMap="StudentResult">
select * from t_student
<where>
<if test="gradeId!=null">
gradeId=#{gradeId}
</if>
<if test="name!=null">
and name like #{name}
</if>
<if test="age!=nulll">
and age=#{age}
</if>
</where>
</select>

4、trim条件

功能和where 元素类似，提供了前缀，后缀功能，更加灵活；

<select id="searchStudents4" parameterType="Map" resultMap="StudentResult">
select * from t_student
<trim prefix="where" prefixOverrides="and|or">
<if test="gradeId!=null">
gradeId=#{gradeId}
</if>
<if test="name!=null">
and name like #{name}
</if>
<if test="age!=nulll">
and age=#{age}
</if>
</trim>
</select>

5、foreach 循环

select * from t_student

<where>

gradeId in

#{gradeId}

</foreach>

</where>

</if>

</select>

6、set条件

1，自动加上set；

2，自动剔除最后一个逗号“，”；

update t_student

<set>

name=#{name},

</if>

age=#{age},

</if>

</set>

where id=#{id}

</update>

五、分页

1，逻辑分页；

@Test

public void testFindStudent(){

logger.info("查询学生");

int offset=0,limit=3;

RowBounds rowBounds=new RowBounds(offset,limit);

List<Student> studentList=studentMapper.findStudents(rowBounds);

for(Student student:studentList){

System.out.println(student);

}

2，物理分页；

select * from t_student

limit #{start},#{size}

</if>

</select>

@Test

public void testFindStudent2(){

logger.info("查询学生");

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

map.put("start", 3);

map.put("size", 3);

List<Student> studentList=studentMapper.findStudents2(map);

for(Student student:studentList){

System.out.println(student);

}

六、缓存

Mybatis 默认情况下，MyBatis 启用一级缓存，即同一个SqlSession 接口对象调用了相同的select 语句，则直

接会从缓存中返回结果，而不是再查询一次数据库；

开发者可以自己配置二级缓存，二级缓存是全局的；

默认情况下，select 使用缓存的，insert update delete 是不使用缓存的

<!--

1，size:表示缓存cache中能容纳的最大元素数。默认是1024；

2，flushInterval:定义缓存刷新周期，以毫秒计；

3，eviction:定义缓存的移除机制；默认是LRU(least recently userd，最近最少使用),还有FIFO(first in first out，先进先出)

4，readOnly:默认值是false，假如是true的话，缓存只能读。

-->

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