Mybatis Notes

Mybatis First

创建Maven项目

配置依赖

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>RELEASE</version>
    </dependency>
</dependencies>

log4j配置

src\main\resources\log4j.properties

log4j.rootLogger=DEBUG
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = [%-5p] %m%n
log4j.logger.test=debug,console

jdbc配置文件

src\main\resources\jdbc.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8
jdbc.name=root
jdbc.password=123456

主配置文件

src\main\resources\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>
    <!--导入jdbc配置文件-->
    <properties resource="jdbc.properties" />
    <!--别名-->
    <typeAliases>
        <!--两种方式-->
        <!--<typeAlias type="com.hex.model.Student" alias="xxx" />-->
        <package name="com.hex.model" />
    </typeAliases>
    <!--配置数据库环境-->
    <environments default="mysql_env">
        <environment id="mysql_env">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.name}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--导入sql映射文件-->
    <mappers>
        <mapper resource="mapper.xml"/>
    </mappers>
</configuration>

mapper映射文件

src\main\resources\mapper.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.hex.model.Student">
    <!--values里面填的是属性(setget方法名去掉setget首字母小写)-->
    <insert id="insertStudent" parameterType="Student">
        insert into student(name,age,score) values (#{name},#{age},#{score})
    </insert>
    <delete id="deleteStudentById" parameterType="int">
        DELETE FROM student WHERE id=#{id}
    </delete>
    <delete id="deleteStudentByName" parameterType="string">
        DELETE FROM student WHERE NAME=#{name}
    </delete>
    <select id="searchStudentById" parameterType="int" resultType="Student">
        SELECT * FROM student WHERE id=#{id}
    </select>
    <select id="searchStudentByName" parameterType="string" resultType="Student">
        SELECT * FROM student WHERE NAME=#{name}
    </select>
    <select id="modifyStudent" parameterType="Student">
        UPDATE student SET NAME=#{name},age=#{age},score=#{score} where id=#{id}
    </select>
    <select id="fuzzyQueryByName" parameterType="string" resultType="Student">
        SELECT * FROM student WHERE NAME LIKE '%${value}%'
    </select>
</mapper>

实体类

com.hex.model.Student

public class Student {
    private Integer id;
    private String name;
    private int age;
    private double score;
    public Student() {}
    public Student(String name, int age, double score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }
    /* 省略set、get方法 */
}

dao层

com.hex.dao.StudentDao

package com.hex.dao;
import com.hex.model.Student;
import com.hex.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import javax.sound.midi.SoundbankResource;
import java.util.ArrayList;
import java.util.List;
public class StudentDao {
    private SqlSession sqlSession;
    public void insertStudent(Student student){
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            sqlSession.insert("insertStudent",student);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
    }
    public void deleteStudentById(int id){
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            sqlSession.delete("deleteStudentById",id);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
    }
    public void deleteStudentByName(String name){
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            sqlSession.delete("deleteStudentByName",name);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
    }
    public List<Student> searchStudentById(int id){
        List<Student> studentList  = new ArrayList<Student>();
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            studentList = sqlSession.selectList("searchStudentById",id);
        }finally {
            sqlSession.close();
            return studentList;
        }
    }
    public List<Student> searchStudentByName(String name){
        List<Student> studentList  = new ArrayList<Student>();
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            studentList = sqlSession.selectList("searchStudentByName",name);
        }finally {
            sqlSession.close();
            return studentList;
        }
    }
    public void modifyStudent(Student student){
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            sqlSession.update("modifyStudent",student);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
    }
    public List<Student> fuzzyQueryByName(String word){
        List<Student> studentList  = new ArrayList<Student>();
        try{
            sqlSession = MybatisUtils.sqlSessionFactory();
            studentList = sqlSession.selectList("fuzzyQueryByName",word);
        }finally {
            sqlSession.close();
            return studentList;
        }
    }
}

工具类

com.hex.utils.MybatisUtils

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 java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    /**
     * 读取主配置文件，创建SqlSession，如果SqlSession已经存在则直接返回
     * @return
     */
    public static SqlSession sqlSessionFactory() {
        try {
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            if (sqlSessionFactory == null) {
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
            }
            return sqlSessionFactory.openSession();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

测试类

com.hex.test.MyTest

import com.hex.dao.StudentDao;
import com.hex.model.Student;
import org.junit.Test;
import java.io.IOException;
public class MyTest {
    private StudentDao dao = new StudentDao();
    @Test
    public void test() throws IOException {
        Student student = new Student("hex",23,98.5);
        dao.insertStudent(student);
    }
    /*省略其他测试方法*/
}

单表的CURD操作

sql语句拼接

<select id="fuzzyQueryByName" parameterType="string" resultType="Student">
    SELECT * FROM student WHERE NAME like '%' #{word} '%'
</select>
<select id="fuzzyQueryByName" parameterType="string" resultType="Student">
    SELECT * FROM student WHERE NAME like concat('%',#{word},'%')
</select>
<!--第3中方法难以避免sql注入问题-->
<select id="fuzzyQueryByName" parameterType="string" resultType="Student">
    SELECT * FROM student WHERE NAME LIKE '%${value}%'
</select>

resultMap

<resultMap id="studentMapper" type="Student">
    <id column="tid" property="id" />
    <result column="tname" property="name" />
</resultMap>
<select id="searchStudentById" resultMap="studentMapper">
    SELECT tid,tname,tage,score FROM student WHERE id=#{id}
</select>

数据库字段名和实体类属性名不一致：将数据库的tid、tname、tage、score封装到Student(id,name,age,score)对象中

mapper动态代理

一般流程
dao对象调用dao层接口的实现类 -> sqlSession.insert(映射器id,映射器需要的参数) -> mapper中对应id的sql语句
mapper的动态代理
new sqlSession -> dao = sqlSession.getMapper(dao层接口.class) -> dao调用接口

通常dao层接口的实现类里面定义了sqlSession去指定mapper.xml映射文件中的哪一个映射方法。然后mapper的动态代理要设置mapper的命名空间，sqlSession.getMapper(dao层接口.class)就相当于指定要找该指定命名空间的映射器。可是映射文件里面定义了那么多select、insert等查询语句，怎么调用我要的呢？这个时候就可以直接用dao对象调用接口，因为接口名和sql语句名是相同的，就可以定位到相应的sql语句。看上去好像是dao直接执行sql语句一样。

两个关键：mapper的命名空间是接口类的全限定类名。接口的方法名和mapper中定义的查询语句的id要保持一致。

@Test
public void mapperDynamicProxy(){
        SqlSession sqlSession = MybatisUtils.sqlSessionFactory();
        StudentDao dao = sqlSession.getMapper(StudentDao.class);
        Student student = dao.selectStudentById(1);
        System.out.println(student.getName());
}

多条件查询

把查询条件封装成实体类的对象
把查询条件封装成Map
索引

#{}中可以放什么内容：
1.参数对象的属性
2.随意内容，此时的#{}是个占位符
3.参数为Map时的key
4.参数为Map时key所对应的value为对象，则可将该对象的属性放入
5.参数的索引号

动态SQL

原符号	<	<=	>	>=	&	'	"
替换符号	`<`	`<=`	`>`	`>=`	`&`	`'`	`"`

<select id="selectStudentByCondition" resultType="Student">
  select * form student
  <where>
      <if test="name != null and name != ''">
          and name like '%' #{name} '%'
      </if>
      <if test="age &gt; 0">
          and age > #{age}
      </if>
  </where>
</select>

choose, when, otherwise

<select id="selectStudentByCondition" resultType="Student">
    select * form student
    <where>
        <choose>
            <when test="name != null and name != ''">
                and name like '%' #{name} '%'
            </when>
            <when test="age &gt; 0">
                and age > #{age}
            </when>
            <otherwise>
                1 = 2
            </otherwise>
        </choose>
    </where>
</select>

trim, where, set

foreach

<!--遍历数组-->
<select id="selectStudentByCondition" resultType="Student">
    select * form student
    <if test="array.length > 0">
        where id in
        <foreach collection="array" item="myid" open="(" close=")" separator=",">
            #{myid}
        </foreach>
    </if>
</select>
<!--遍历list-->
<select id="selectStudentByCondition" resultType="Student">
    select * form student
    <if test="list.size > 0">
        where id in
        <foreach collection="list" item="myid" open="(" close=")" separator=",">
            #{myid}
        </foreach>
    </if>
</select>

bind

sql片段

<sql id="selectColumns">id,name,age,score</sql>
<select id="selectStudentByCondition" resultType="Student">
    select <include refid="selectColumns" /> form student
</select>

关联关系查询

一对多

创建数据表和实体类

	country	minister
结构	cid、cname	mid、mname、countryid
关系	一	多

mapper映射文件

<mapper namespace="com.one2many.dao.CountryDao">
    <resultMap id="countryMapper" type="Country">
        <id column="cid" property="cid" />
        <result column="cname" property="cname"/>
        <collection property="ministers" ofType="Minister">
            <id column="mid" property="mid"/>
            <result column="mname" property="mname" />
        </collection>
    </resultMap>
    <select id="selectCountryById" resultMap="countryMapper" parameterType="int">
        SELECT cid,cname,mid,mname FROM country,minister WHERE cid = countryid and cid = #{id}
    </select>
</mapper>

测试类

@Test
public void test01(){
    SqlSession sqlSession = MybatisUtils.sqlSessionFactory();
    CountryDao dao = sqlSession.getMapper(CountryDao.class);
    Country country = dao.selectCountryById(1);
    System.out.println(country.toString());
}

mapper还可以这样写，一个集合的值是从另外一个select语句的结果得到的

<mapper namespace="com.one2many.dao.CountryDao">
    <select id="selectMinisterByCountry" resultType="Minister">
        select mid,mname from minister where countryid = #{xxx}
    </select>
    <resultMap id="countryMapper" type="Country">
        <id column="cid" property="cid" />
        <result column="cname" property="cname"/>
        <collection property="ministers"
                    ofType="Minister"
                    select="selectMinisterByCountry"
                    column="cid"/>
    </resultMap>
    <select id="selectCountryById" resultMap="countryMapper" parameterType="int">
        SELECT cid,cname,mid,mname FROM country,minister WHERE cid = countryid and cid = #{id}
    </select>
</mapper>

多对一

创建数据表和实体类

	country	minister
结构	cid、cname	mid、mname、country
关系	多	一

mapper映射文件

<mapper namespace="com.many2one.dao.MinisterDao">
    <resultMap id="ministerMapper" type="Minister">
        <id column="mid" property="mid" />
        <result column="mname" property="mname" />
        <association property="country" javaType="Country">
            <!--property映射成javaType-->
            <id column="cid" property="cid" />
            <result column="cname" property="cname" />
        </association>
    </resultMap>
    <select id="selectMinisterById" resultMap="ministerMapper">
        SELECT MID,mname,cid,cname FROM minister,country
        WHERE countryid = cid AND MID = #{xxx}
    </select>
</mapper>

测试类

@Test
public void test01(){
    SqlSession sqlSession = MybatisUtils.sqlSessionFactory();
    MinisterDao dao = sqlSession.getMapper(MinisterDao.class);
    Minister minister = dao.selectMinisterById(2);
    System.out.println(minister.toString());
}

mapper还可以这样写，一个关联的值是从另外一个select语句的结果得到的

<mapper namespace="com.many2one.dao.MinisterDao">
    <select id="selectCountryById" resultType="Country">
        select cid,cname FROM country where cid=#{xxx}
    </select>
    <resultMap id="ministerMapper" type="Minister">
        <id column="mid" property="mid" />
        <result column="mname" property="mname" />
        <association property="country"
                     javaType="Country"
                     select="selectCountryById" column="countryid">
        </association>
    </resultMap>
    <select id="selectMinisterById" resultMap="ministerMapper">
        SELECT MID,mname,countryid FROM minister WHERE MID = #{xxx}
    </select>
</mapper>

自关联

NewsLabel模型

public class NewsLabel {
    private int id;
    private String name;
    private Set<NewsLabel> children;
    /*省略set、get、toString方法*/
}

<mapper namespace="com.hex.dao.NewsLabelDao">
    <resultMap id="newslabelMapper" type="NewsLabel">
        <id column="id" property="id" />
        <result column="name" property="name"/>
        <collection property="children"
                    ofType="NewsLabel"
                    select="selectChildrenByParent"
                    column="id" />
    </resultMap>
    <select id="selectChildrenByParent" resultMap="newslabelMapper">
        select id,name FROM newslabel where pid=#{xxx}
    </select>
</mapper>

@Test
public void test01(){
    SqlSession sqlSession = MybatisUtils.sqlSessionFactory();
    NewsLabelDao dao = sqlSession.getMapper(NewsLabelDao.class);
    List<NewsLabel> list = dao.selectChildrenByParent(2);
    for (NewsLabel li:list) {
        System.out.println(li.toString());
    }
}

多对多

延迟加载

<settings>
    <setting name="lazyLoadingEnable" value="false" />
    <setting name="aggressiveLazyLoading" value="false" />
</settings>

查询缓存

一级缓存、二级缓存

ehcache

导包

<dependency>
    <groupId>net.sf.ehcache</groupId>
    <artifactId>ehcache</artifactId>
    <version>2.8.3</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-ehcache</artifactId>
    <version>1.0.0</version>
</dependency>

引入ehcache类
xml <mapper> <cache type="org.mybatis.caches.ehcache.EhcacheCache" /> </mapper>
导入配置文件

把ehcache-core里面的配置文件导入项目

Mybatis注解式开发(dao层接口)

@Insert(value="")
@Delete(value="")
@Update(value="")
@Select(value="")

<mapper>
    <!--映射文件所在的包-->
    <package name="com.hex.dao" /> 
</mapper>

SSM学习（一）Mybatis

Mybatis Notes

Mybatis First

创建Maven项目

log4j配置

jdbc配置文件

主配置文件

mapper映射文件

实体类

dao层

工具类

测试类

单表的CURD操作

sql语句拼接

resultMap

mapper动态代理

多条件查询

动态SQL

sql片段

关联关系查询

一对多

多对一

自关联

多对多

延迟加载

查询缓存

一级缓存、二级缓存

ehcache

Mybatis注解式开发(dao层接口)

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