Summary of mybatis framework of java-SSM framework
1. Project
1. Database preparation
CREATE table blog(
id VARCHAR(50) not NULL COMMENT '博客id',
title VARCHAR(199) not null COMMENT '博客标题',
author varchar(30) not null COMMENT '博客作者',
createTime datetime not NULL COMMENT '创建时间',
views int(30) not null COMMENT '浏览量'
) ENGINE=INNODB DEFAULT CHARSET=utf8
SHOW tables;
SELECT * from blog;
use mybatis;
CREATE table teacher(
id int(10) not NULL,
`name` varchar(30) DEFAULT NULL,
PRIMARY key(id)
)ENGINE=INNODB DEFAULT charset=utf8;
insert into teacher(id,name) values(1,'秦老师');
CREATE table student(
id int(10) not NULL,
`name` VARCHAR(30) DEFAULT NULL,
tid int(10) DEFAULT NULL,
PRIMARY key(id),
KEY fktid (tid),
CONSTRAINT fktid FOREIGN key(tid) REFERENCES teacher (id)
)ENGINE=INNODB DEFAULT charset=utf8;
insert into student(id,name,tid) values
(1,'小明',1),
(2,'小王',1),
(3,'小李',1),
(4,'小廖',1),
(5,'小周',1)
2. Idea environment construction
Import the jar package in prom.xml under the parent module, and all the sub-projects created later will have these jar packages
Project catalog
Examples of main points of parent porm.xml and child porm.xml
//父porm.xml有子模块的架构
<modules>
<module>mybatis-01</module>
<module>mybatis-03</module>
<module>mybatis-04</module>
<module>mybatis-1more</module>
<module>mybatis-project</module>
</modules>
//子porm.xml有父模块的标记
<parent>
<artifactId>Mybatis-Study</artifactId>
<groupId>org.example</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
//解决资源文件无法被导出到target
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
mybatis.config.xml core configuration file
Note: The order of configuration is specified here!
<?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>
//读取数据库属性配置文件db.properties
<properties resource="db.properties"/>
//设置日志和数据表字段与实体类的驼峰和下划线互转的配置
<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
<setting name="mapUnderscoreToCamelCase" value="true" />
</settings>
//属性配置之别名优化
<typeAliases>
<package name="com.com.huang.pojo"/>
</typeAliases>
//配置运行的环境
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
//Mapper接口对应的xml文件必须要在此处注册，有三种写法
//我们通常使用class，但前提是Mapper接口和对应的xml文件在一个包下，且名字一样
<mappers>
<mapper class="com.com.huang.dao.StudentMapper"/>
<mapper class="com.com.huang.dao.TeacherMapper"/>
</mappers>
</configuration>
MybatisUtils tool class to obtain sqlSession object
package com.huang.utils;
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 {
public static SqlSessionFactory sqlSessionFactory;
static {
try {
InputStream inputStream = Resources.getResourceAsStream("mybatis.config.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
//此处设置布尔值true，增删改就无需sqlSession.commit()提交事务了
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession(true);
}
}
Database properties configuration file db.properties
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/${需要连接的数据库名如：mybatis}?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=${数据库用户名}
password=${数据库密码}
Mapper interface example
package com.huang.dao;
import com.huang.pojo.Student;
import java.util.List;
public interface StudentMapper {
// 多对一（学生对老师）的处理---按照查询嵌套处理
List<Student> getStudent();
// 多对一（学生对老师）的处理---按照查询嵌套处理
List<Student> getStudent2();
}
Mapper接口对应的xml文件示例
<?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">
//namespace为相对路径下的Mapper接口
<mapper namespace="com.huang.dao.StudentMapper">
//此处编写sql语句，示例
<select id="getStudent" resultMap="StudentTeacher">
select * from mybatis.student;
</select>
</mapper>
Supplement the configuration of lombok plugin
1. Install the lombok plugin
2. Configure dependencies in sub-porm.xml
<dependencies>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
</dependency>
</dependencies>
3. Just use the annotation @Data, see the use of entity classes
After completing the above environment construction, we can start testing
1. Test Directory
2. Test example
// 测试环境搭建成功
@Test
public void test1(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
List<Teacher> teacherList = mapper.getTeacher();
for (Teacher teacher : teacherList) {
System.out.println(teacher);
}
sqlSession.close();
}
3. Many-to-one processing
Entity class pojo
package com.huang.pojo;
import lombok.Data;
@Data
public class Teacher {
private int id;
private String name;
}
package com.huang.pojo;
import lombok.Data;
@Data
public class Student {
private int id;
private String name;
// 外键关联的老师对象
private Teacher teacher;
}
1. Follow query nesting processing
<select id="getStudent" resultMap="StudentTeacher">
select * from mybatis.student;
</select>
<resultMap id="StudentTeacher" type="Student">
<result property="id" column="id"/>
<result property="name" column="name"/>
//注意一下固定写法
<association property="teacher" column="tid" javaType="teacher" select="getSTeacher"/>
</resultMap>
// #{tid}中tid可以为任何内容
<select id="getSTeacher" resultType="Teacher">
select * from mybatis.teacher where id = #{tid};
</select>
2. Nested processing according to the results
<select id="getStudent2" resultMap="Student2Teacher2">
select s.id sid,s.name sname,t.name tname from mybatis.student s,mybatis.teacher t where s.tid = t.id;
</select>
<resultMap id="Student2Teacher2" type="student">
<result property="id" column="sid"/>
<result property="name" column="sname"/>
<association property="teacher" javaType="teacher">
<result property="name" column="tname"/>
</association>
</resultMap>
4. Many-to-one processing (the corresponding mapper and xml files are not given below)
Entity class pojo
package com.huang.pojo;
import lombok.Data;
@Data
public class Teacher {
private int id;
private String name;
private List<Student> students;
}
package com.huang.pojo;
import lombok.Data;
@Data
public class Student {
private int id;
private String name;
private int tid;
}
1. Follow query nesting processing
<select id="getTeacher2" resultMap="TeacherStudent2">
select * from mybatis.teacher where id = #{id};
</select>
<resultMap id="TeacherStudent2" type="Teacher"
<collection property="students" column="id" javaType="ArrayList" ofType="Student" select="getStudentByTeacherId"/>
</resultMap>
// #{id}中id可以为任何内容
<select id="getStudentByTeacherId" resultType="Student">
select * from mybatis.student where tid = #{id};
</select>
2. Nested processing according to the results
<select id="getTeacher" resultMap="TeacherStudent">
select s.id sid,s.name sname,t.name tname,t.id tid
from student s,teacher t
where s.tid = t.id and t.id = #{id};
</select>
<resultMap id="TeacherStudent" type="Teacher">
<result property="id" column="tid"/>
<result property="name" column="tname"/>
<collection property="students" ofType="Student">
<result property="id" column="sid"/>
<result property="name" column="sname"/>
<result property="tid" column="tid"/>
</collection >
</resultMap>
5. Dynamic sql
1. if statement
<select id="getStudent" resultType="student">
SELECT * FROM mybatis.student
<if test="name!=null">
AND name = #{name}
</if>
</select>
2.where tag
<select id="getStudent" resultType="student" parameterType="map">
SELECT * mybatis.student
//where会自动添加或者删除and,choose和when满足一个就不会继续往后，
//类似switch，case/break
<where>
<choose>
<when test="name!= null">
AND name = #{name}
</when>
<when test="tid != null">
AND tid =#{tid }
</when>
<otherwise>
AND id= "2"
</otherwise>
</choose>
</where>
</select>
3.set tag
<update id="updateEmprById2" parameterType="emp">
UPDATE mybatis.student
//set会自动添加或者删除,保证sql语句的合法性
<set>
<if test="name!=null"> name=#{name},</if>
<if test="tid!=null"> tid=#{tid},</if>
</set>
where id = #{id}
</update>
6. Add some points
One. Mybatis realizes paging mode 1
//1.接口
List<User> getUserListByLimit(Map<String,Integer> map);
//2.mapper.xml配置
//配合使用结果集映射，解决字段名不一致的问题
<resultMap id="UserMap" type="user">
<result property="password" column="pwd"/>
</resultMap>
<select id="getUserListByLimit" resultMap="UserMap">
select * from mybatis.user limit #{startIndex},#{pageSize};
</select>
//3.测试类
@Test
public void testLimit(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userdao = sqlSession.getMapper(UserDao.class);
Logger logger = Logger.getLogger(UserDaoTest.class);
logger.info("info:用分页来查询数据");
HashMap<String, Integer> map = new HashMap<>();
map.put("startIndex",0);
map.put("pageSize",2);
List<User> userList = userdao.getUserListByLimit(map);
for (User user : userList) {
System.out.println(user);
}
sqlSession.close();
}
Two. Mybatis realizes paging mode 2
//1.接口
List<User> getUserListByRowBounds();
//2.mapper.xml配置
//配合使用结果集映射
<resultMap id="UserMap" type="user">
<result property="password" column="pwd"/>
</resultMap>
<select id="getUserListByRowBounds" resultMap="UserMap">
//此处要查询全部
select * from mybatis.user;
</select>
//3.测试类
@Test
public void testRowBounds(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
// RowBounds实现
RowBounds rowBounds = new RowBounds(0, 1);
logger.info("info:使用RowBounds来进行分页");
// Java代码层面实现分页 这里是sqlSession执行sql语言的第二种方式，（不推荐）
List<User> userList = sqlSession.selectList("com.huang.dao.UserDao.getUserListByRowBounds", null, rowBounds);
for (User user : userList) {
System.out.println(user);
}
sqlSession.close();
}
Three. Fuzzy query
//Mapper接口
List<User> getUserListByNameLike(String name);
//模糊查询
<select id="getUserListByNameLike" resultType="user">
select * from mybatis.user where name like concat("%",#{name},"%");
</select>
//测试类
@Test
public void testLike(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
//测试模糊查询
//方式一：List<User> userList = userDao.getUserListByNameLike("%王%");
List<User> userList = userDao.getUserListByNameLike("王");
for (User user : userList) {
System.out.println(user);
}
sqlSession.close();
}
Four.map parameters
//Mapper接口
List<User> getUserListById2(Map<String,Object> map);
//使用map可以自定义参数名
<select id="getUserListById2" resultType="user" parameterType="map">
select * from mybatis.user where id = #{selfDefinedField};
</select>
//测试类
@Test
public void test0(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("selfDefinedField",5);
List<User> userList = userDao.getUserListById2(map);
for (User user : userList) {
System.out.println(user);
}
sqlSession.close();
}
Five. Comments
//增加一个用户 注解适用于简单的业务逻辑
@Insert("insert into user(id,name,pwd) values(#{id},#{name},#{password})")
int insertUser(User user);
Six. Log4j log
1. Import the jar package
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
2. Create a new log4j.properties configuration file under resource
# priority :debug<info<warn<error
#you cannot specify every priority with different file for log4j
log4j.rootLogger=debug,stdout,info,debug,warn,error
#console
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern= [%d{yyyy-MM-dd HH:mm:ss a}]:%p %l%m%n
#info log
log4j.logger.info=info
log4j.appender.info=org.apache.log4j.DailyRollingFileAppender
log4j.appender.info.DatePattern='_'yyyy-MM-dd'.log'
log4j.appender.info.File=./src/log/info.log
log4j.appender.info.Append=true
log4j.appender.info.Threshold=INFO
log4j.appender.info.layout=org.apache.log4j.PatternLayout
log4j.appender.info.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss a} [Thread: %t][ Class:%c >> Method: %l ]%n%p:%m%n
#debug log
log4j.logger.debug=debug
log4j.appender.debug=org.apache.log4j.DailyRollingFileAppender
log4j.appender.debug.DatePattern='_'yyyy-MM-dd'.log'
log4j.appender.debug.File=./src/log/debug.log
log4j.appender.debug.Append=true
log4j.appender.debug.Threshold=DEBUG
log4j.appender.debug.layout=org.apache.log4j.PatternLayout
log4j.appender.debug.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss a} [Thread: %t][ Class:%c >> Method: %l ]%n%p:%m%n
#warn log
log4j.logger.warn=warn
log4j.appender.warn=org.apache.log4j.DailyRollingFileAppender
log4j.appender.warn.DatePattern='_'yyyy-MM-dd'.log'
log4j.appender.warn.File=./src/log/warn.log
log4j.appender.warn.Append=true
log4j.appender.warn.Threshold=WARN
log4j.appender.warn.layout=org.apache.log4j.PatternLayout
log4j.appender.warn.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss a} [Thread: %t][ Class:%c >> Method: %l ]%n%p:%m%n
#error
log4j.logger.error=error
log4j.appender.error = org.apache.log4j.DailyRollingFileAppender
log4j.appender.error.DatePattern='_'yyyy-MM-dd'.log'
log4j.appender.error.File = ./src/log/error.log
log4j.appender.error.Append = true
log4j.appender.error.Threshold = ERROR
log4j.appender.error.layout = org.apache.log4j.PatternLayout
log4j.appender.error.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss a} [Thread: %t][ Class:%c >> Method: %l ]%n%p:%m%n
3. Configure in the mybatis.config.xml core configuration file
<settings>
<setting name="logImpl" value="LOG4J"/>
//解决驼峰转数据库中的_
<setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
4. Test in the test class
static Logger logger = Logger.getLogger(类对象【Student.class】)
logger.info("info：进入了信息输出");
logger.debug("debug:进入了debug阶段");
logger.error("error:进入了error阶段");
@Test
public void test1(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userdao = sqlSession.getMapper(UserDao.class);
List<User> userlist = userdao.getUserListById(1);
logger.info("info：进入了信息输出");
for (User user : userlist) {
System.out.println(user);
}
sqlSession.close();
}
@Test
public void test2(){
logger.info("info：进入了信息输出");
}
5. Finally, a log file will be generated at the location specified by log4j.properties
