<dependencies>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.5.7version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
<scope>testscope>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.3version>
dependency>
dependencies>
习惯上命名为
mybatis-config.xml
,这个文件名仅仅只是建议,并非强制要求。将来整合Spring之后,这个配置文件可以省略,所以大家操作时可以直接复制、粘贴。
核心配置文件主要用于配置连接数据库的环境以及MyBatis的全局配置信息
核心配置文件存放的位置是src/main/resources目录下
DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="dy"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="mappers/UserMapper.xml"/>
mappers>
configuration>
MyBatis中的mapper接口相当于以前的dao。但是区别在于,mapper仅仅是接口,我们不需要提供实现类
package com.atguigu.mybatis.mapper;
public interface UserMapper {
/**
* Mybatis 面向接口编程的两个一致:
* 1.映射文件的namespace要和mapper接口的全类名保持一致
* 2.映射文件中SQL语句的id要和mapper接口中的方法名一致
*/
//添加用户信息
int insertUser();
}
package com.atguigu.mybatis.pojo;
public class User {
private Integer id;
private String username;
private String password;
private Integer age;
private String sex;
private String email;
public User(){
}
public User(Integer id, String username, String password, Integer age, String sex, String email) {
this.id = id;
this.username = username;
this.password = password;
this.age = age;
this.sex = sex;
this.email = email;
}
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 Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", age=" + age +
", sex='" + sex + '\'' +
", email='" + email + '\'' +
'}';
}
}
Java概念 | 数据库概念 |
---|---|
类 | 表 |
属性 | 字段/列 |
对象 | 记录/行 |
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.atguigu.mybatis.mapper.UserMapper">
<insert id="insertUser">
insert into t_user values(null,'张三','123',23,'女')
insert>
mapper>
public class UserMapperTest {
@Test
public void testInsertUser() throws IOException {
//读取MyBatis的核心配置文件
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
//获取SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
//通过核心配置文件所对应的字节输入流创建工厂类SqlSessionFactory,生产SqlSession对象
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
//获取sqlSession,此时通过SqlSession对象所操作的sql都必须手动提交或回滚事务
//SqlSession sqlSession = sqlSessionFactory.openSession();
//创建SqlSession对象,此时通过SqlSession对象所操作的sql都会自动提交
SqlSession sqlSession = sqlSessionFactory.openSession(true);
//通过代理模式创建UserMapper接口的代理实现类对象
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//调用UserMapper接口中的方法,就可以根据UserMapper的全类名匹配元素文件,通过调用的方法名匹配映射文件中的SQL标签,并执行标签中的SQL语句
int result = userMapper.insertUser();
//提交事务
//sqlSession.commit();
System.out.println("result:" + result);
}
}
SqlSession sqlSession = sqlSessionFactory.openSession(true);
,传入一个Boolean类型的参数,值为true,这样就可以自动提交加入依赖
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
加入log4j的配置文件
DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
<param name="Encoding" value="UTF-8" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" />
layout>
appender>
<logger name="java.sql">
<level value="debug" />
logger>
<logger name="org.apache.ibatis">
<level value="info" />
logger>
<root>
<level value="debug" />
<appender-ref ref="STDOUT" />
root>
log4j:configuration>
<insert id="insertUser">
insert into t_user values(null,'admin','123456',23,'男','[email protected]')
insert>
<delete id="deleteUser">
delete from t_user where id = 6
delete>
<update id="updateUser">
update t_user set username = '张三' where id = 5
update>
<select id="getUserById" resultType="com.atguigu.mybatis.bean.User">
select * from t_user where id = 2
select>
<select id="getUserList" resultType="com.atguigu.mybatis.bean.User">
select * from t_user
select>
- 查询的标签select必须设置属性resultType或resultMap,用于设置实体类和数据库表的映射关系
- resultType:自动映射,用于属性名和表中字段名一致的情况
- resultMap:自定义映射,用于一对多或多对一或字段名和属性名不一致的情况
- 当查询的数据为多条时,不能使用实体类作为返回值,只能使用集合,否则会抛出异常TooManyResultsException;但是若查询的数据只有一条,可以使用实体类或集合作为返回值
核心配置文件中的标签必须按照固定的顺序(有的标签可以不写,但顺序一定不能乱):
properties、settings、typeAliases、typeHandlers、objectFactory、objectWrapperFactory、reflectorFactory、plugins、environments、databaseIdProvider、mappers
DOCTYPE configuration
PUBLIC "-//MyBatis.org//DTD Config 3.0//EN"
"http://MyBatis.org/dtd/MyBatis-3-config.dtd">
<configuration>
<properties resource="jdbc.properties">properties>
<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/>
<setting name="lazyLoadingEnabled" value="true"/>
settings>
<typeAliases>
<package name="com.atguigu.mybatis.bean"/>
typeAliases>
<environments default="mysql_test">
<environment id="mysql_test">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
dataSource>
environment>
environments>
<mappers>
<package name="com.atguigu.mybatis.mapper"/>
mappers>
configuration>
注意:以包为单位时mapper接口和mapper映射文件在同一包下
先编写mybatis-config.xml文件
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.atguigu.mybatis.pojo"/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
dataSource>
environment>
environments>
<mappers>
<package name="com/atguigu/mybatis/mapper"/>
mappers>
configuration>
创建模板:
将上述代码复制到模板中
编写xml文件:
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="">
mapper>
<select id="getUserByUsername" resultType="User">
select * from t_user where username = #{username}
select>
<select id="getUserByUsername" resultType="User">
select * from t_user where username = '${username}'
select>
- 以arg0,arg1…为键,以参数为值;
- 以param1,param2…为键,以参数为值;
<select id="checkLogin" resultType="User">
select * from t_user where username = #{arg0} and password = #{arg1}
select>
<select id="checkLogin" resultType="User">
select * from t_user where username = '${param1}' and password = '${param2}'
select>
<select id="checkLoginByMap" resultType="User">
select * from t_user where username = #{username} and password = #{password}
select>
@Test
public void checkLoginByMap() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
Map<String,Object> map = new HashMap<>();
map.put("usermane","admin");
map.put("password","123456");
User user = mapper.checkLoginByMap(map);
System.out.println(user);
}
<insert id="insertUser">
insert into t_user values(null,#{username},#{password},#{age},#{sex},#{email})
insert>
@Test
public void insertUser() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
User user = new User(null,"Tom","123456",12,"男","[email protected]");
mapper.insertUser(user);
}
注意:实体类型的属性看的是get和set方法,而不是成员变量
- 以@Param注解的value属性值为键,以参数为值;
- 以param1,param2…为键,以参数为值;
<select id="CheckLoginByParam" resultType="User">
select * from t_user where username = #{username} and password = #{password}
select>
@Test
public void checkLoginByParam() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);
mapper.CheckLoginByParam("admin","123456");
}
总结
- 实体类类型的参数
- 使用@Param标识参数
{password=123456, sex=男, id=1, age=23, username=admin}
/**
* 根据用户id查询用户信息
* @param id
* @return
*/
User getUserById(@Param("id") int id);
<select id="getUserById" resultType="User">
select * from t_user where id = #{id}
select>
/**
* 查询所有用户信息
* @return
*/
List<User> getUserList();
<select id="getUserList" resultType="User">
select * from t_user
select>
/**
* 查询用户的总记录数
* @return
* 在MyBatis中,对于Java中常用的类型都设置了类型别名
* 例如:java.lang.Integer-->int|integer
* 例如:int-->_int|_integer
* 例如:Map-->map,List-->list
*/
int getCount();
<select id="getCount" resultType="_integer">
select count(id) from t_user
select>
/**
* 根据用户id查询用户信息为map集合
* @param id
* @return
*/
Map<String, Object> getUserToMap(@Param("id") int id);
<select id="getUserToMap" resultType="map">
select * from t_user where id = #{id}
select>
/**
* 查询所有用户信息为map集合
* @return
* 将表中的数据以map集合的方式查询,一条数据对应一个map;若有多条数据,就会产生多个map集合,此时可以将这些map放在一个list集合中获取
*/
List<Map<String, Object>> getAllUserToMap();
<select id="getAllUserToMap" resultType="map">
select * from t_user
select>
/**
* 查询所有用户信息为map集合
* @return
* 将表中的数据以map集合的方式查询,一条数据对应一个map;若有多条数据,就会产生多个map集合,并且最终要以一个map的方式返回数据,此时需要通过@MapKey注解设置map集合的键,值是每条数据所对应的map集合
*/
@MapKey("id")
Map<String, Object> getAllUserToMap();
<select id="getAllUserToMap" resultType="map">
select * from t_user
select>
/**
* 根据用户名进行模糊查询
* @param username
* @return java.util.List
* @date 2022/2/26 21:56
*/
List<User> getUserByLike(@Param("username") String username);
<select id="getUserByLike" resultType="User">
select * from t_user where username like "%"#{mohu}"%"
select>
select * from t_user where username like "%"#{mohu}"%"
是最常用的delete from t_user where id in ('1,2,3')
,这样是将1,2,3
看做是一个整体,只有id为1,2,3
的数据会被删除。正确的语句应该是delete from t_user where id in (1,2,3)
,或者delete from t_user where id in ('1','2','3')
/**
* 根据id批量删除
* @param ids
* @return int
* @date 2022/2/26 22:06
*/
int deleteMore(@Param("ids") String ids);
<delete id="deleteMore">
delete from t_user where id in (${ids})
delete>
//测试类
@Test
public void deleteMore() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
int result = mapper.deleteMore("1,2,3,8");
System.out.println(result);
}
使用#{}会自动加’’ 而${}需要手动加’ ’
/**
* 查询指定表中的数据
* @param tableName
* @return java.util.List
* @date 2022/2/27 14:41
*/
List<User> getUserByTable(@Param("tableName") String tableName);
<select id="getUserByTable" resultType="User">
select * from ${tableName}
select>
使用场景
t_clazz(clazz_id,clazz_name)
在mapper.xml中设置两个属性
useGeneratedKeys:设置使用自增的主键
/**
* 添加用户信息
* @param user
* @date 2022/2/27 15:04
*/
void insertUser(User user);
<insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
insert into t_user values (null,#{username},#{password},#{age},#{sex},#{email})
insert>
//测试类
@Test
public void insertUser() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
User user = new User(null, "ton", "123", 23, "男", "[email protected]");
mapper.insertUser(user);
System.out.println(user);
//输出:user{id=10, username='ton', password='123', age=23, sex='男', email='[email protected]'},自增主键存放到了user的id属性中
}
<resultMap id="empResultMap" type="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
resultMap>
<select id="getAllEmp" resultMap="empResultMap">
select * from t_emp
select>
<select id="getAllEmp" resultType="Emp">
select eid,emp_name empName,age,sex,email from t_emp
select>
setting
标签中,设置一个全局配置信息mapUnderscoreToCamelCase,可以在查询表中数据时,自动将_类型的字段名转换为驼峰,例如:字段名user_name,设置了mapUnderscoreToCamelCase,此时字段名就会转换为userName。<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/>
settings>
查询员工信息以及员工所对应的部门信息
public class Emp {
private Integer eid;
private String empName;
private Integer age;
private String sex;
private String email;
private Dept dept;
//...构造器、get、set方法等
}
<resultMap id="empAndDeptResultMapOne" type="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
<result property="dept.did" column="did">result>
<result property="dept.deptName" column="dept_name">result>
resultMap>
<select id="getEmpAndDept" resultMap="empAndDeptResultMapOne">
select * from t_emp left join t_dept on t_emp.eid = t_dept.did where t_emp.eid = #{eid}
select>
<resultMap id="empAndDeptResultMapTwo" type="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
<association property="dept" javaType="Dept">
<id property="did" column="did">id>
<result property="deptName" column="dept_name">result>
association>
resultMap>
<select id="getEmpAndDept" resultMap="empAndDeptResultMapTwo">
select * from t_emp left join t_dept on t_emp.eid = t_dept.did where t_emp.eid = #{eid}
select>
//EmpMapper里的方法
/**
* 通过分步查询,员工及所对应的部门信息
* 分步查询第一步:查询员工信息
* @param
* @return com.atguigu.mybatis.pojo.Emp
*/
Emp getEmpAndDeptByStepOne(@Param("eid") Integer eid);
<resultMap id="empAndDeptByStepResultMap" type="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
<association property="dept"
select="com.atguigu.mybatis.mapper.DeptMapper.getEmpAndDeptByStepTwo"
column="did">association>
resultMap>
<select id="getEmpAndDeptByStepOne" resultMap="empAndDeptByStepResultMap">
select * from t_emp where eid = #{eid}
select>
//DeptMapper里的方法
/**
* 通过分步查询,员工及所对应的部门信息
* 分步查询第二步:通过did查询员工对应的部门信息
* @param
* @return com.atguigu.mybatis.pojo.Emp
*/
Dept getEmpAndDeptByStepTwo(@Param("did") Integer did);
<resultMap id="EmpAndDeptByStepTwoResultMap" type="Dept">
<id property="did" column="did">id>
<result property="deptName" column="dept_name">result>
resultMap>
<select id="getEmpAndDeptByStepTwo" resultMap="EmpAndDeptByStepTwoResultMap">
select * from t_dept where did = #{did}
select>
查询部门以及部门中所有的员工信息
public class Dept {
private Integer did;
private String deptName;
private List<Emp> emps;
//...构造器、get、set方法等
}
<resultMap id="DeptAndEmpResultMap" type="Dept">
<id property="did" column="did">id>
<result property="deptName" column="dept_name">result>
<collection property="emps" ofType="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
collection>
resultMap>
<select id="getDeptAndEmp" resultMap="DeptAndEmpResultMap">
select * from t_dept left join t_emp on t_dept.did = t_emp.did where t_dept.did = #{did}
select>
/**
* 通过分步查询,查询部门及对应的所有员工信息
* 分步查询第一步:查询部门信息
* @param did
* @return com.atguigu.mybatis.pojo.Dept
* @date 2022/2/27 22:04
*/
Dept getDeptAndEmpByStepOne(@Param("did") Integer did);
<resultMap id="DeptAndEmpByStepOneResultMap" type="Dept">
<id property="did" column="did">id>
<result property="deptName" column="dept_name">result>
<collection property="emps"
select="com.atguigu.mybatis.mapper.EmpMapper.getDeptAndEmpByStepTwo"
column="did">collection>
resultMap>
<select id="getDeptAndEmpByStepOne" resultMap="DeptAndEmpByStepOneResultMap">
select * from t_dept where did = #{did}
select>
/**
* 通过分步查询,查询部门及对应的所有员工信息
* 分步查询第二步:根据部门id查询部门中的所有员工
* @param did
* @return java.util.List
* @date 2022/2/27 22:10
*/
List<Emp> getDeptAndEmpByStepTwo(@Param("did") Integer did);
<select id="getDeptAndEmpByStepTwo" resultType="Emp">
select * from t_emp where did = #{did}
select>
<settings>
<setting name="lazyLoadingEnabled" value="true"/>
settings>
@Test
public void getEmpAndDeptByStepOne() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = mapper.getEmpAndDeptByStepOne(1);
System.out.println(emp.getEmpName());
}
@Test
public void getEmpAndDeptByStepOne() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
Emp emp = mapper.getEmpAndDeptByStepOne(1);
System.out.println(emp.getEmpName());
System.out.println("----------------");
System.out.println(emp.getDept());
}
<resultMap id="empAndDeptByStepResultMap" type="Emp">
<id property="eid" column="eid">id>
<result property="empName" column="emp_name">result>
<result property="age" column="age">result>
<result property="sex" column="sex">result>
<result property="email" column="email">result>
<association property="dept"
select="com.atguigu.mybatis.mapper.DeptMapper.getEmpAndDeptByStepTwo"
column="did"
fetchType="lazy">association>
resultMap>
1=1
1=1
可以用来拼接and
语句,例如:当empName为null时select * from t_emp where and age = ? and sex = ? and email = ?
,此时where
会与and
连用,SQL语句会报错
select * from t_emp where 1= 1 and age = ? and sex = ? and email = ?
,此时不报错
<select id="getEmpByCondition" resultType="Emp">
select * from t_emp where 1=1
<if test="empName != null and empName !=''">
and emp_name = #{empName}
if>
<if test="age != null and age !=''">
and age = #{age}
if>
<if test="sex != null and sex !=''">
and sex = #{sex}
if>
<if test="email != null and email !=''">
and email = #{email}
if>
select>
<select id="getEmpByCondition" resultType="Emp">
select * from t_emp
<where>
<if test="empName != null and empName !=''">
emp_name = #{empName}
if>
<if test="age != null and age !=''">
and age = #{age}
if>
<if test="sex != null and sex !=''">
and sex = #{sex}
if>
<if test="email != null and email !=''">
and email = #{email}
if>
where>
select>
<if test="empName != null and empName !=''">
emp_name = #{empName} and
if>
<if test="age != null and age !=''">
age = #{age}
if>
select * from t_emp
<select id="getEmpByCondition" resultType="Emp">
select * from t_emp
<trim prefix="where" suffixOverrides="and|or">
<if test="empName != null and empName !=''">
emp_name = #{empName} and
if>
<if test="age != null and age !=''">
age = #{age} and
if>
<if test="sex != null and sex !=''">
sex = #{sex} or
if>
<if test="email != null and email !=''">
email = #{email}
if>
trim>
select>
//测试类
@Test
public void getEmpByCondition() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
DynamicSQLMapper mapper = sqlSession.getMapper(DynamicSQLMapper.class);
List<Emp> emps= mapper.getEmpByCondition(new Emp(null, "张三", null, null, null, null));
System.out.println(emps);
}
choose、when、otherwise
相当于if...else if..else
<select id="getEmpByChoose" resultType="Emp">
select * from t_emp
<where>
<choose>
<when test="empName != null and empName != ''">
emp_name = #{empName}
when>
<when test="age != null and age != ''">
age = #{age}
when>
<when test="sex != null and sex != ''">
sex = #{sex}
when>
<when test="email != null and email != ''">
email = #{email}
when>
<otherwise>
did = 1
otherwise>
choose>
where>
select>
@Test
public void getEmpByChoose() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
DynamicSQLMapper mapper = sqlSession.getMapper(DynamicSQLMapper.class);
List<Emp> emps = mapper.getEmpByChoose(new Emp(null, "张三", 23, "男", "[email protected]", null));
System.out.println(emps);
}
if a else if b else if c else d
,只会执行其中一个,
<delete id="deleteMoreByArray">
delete from t_emp where eid in
<foreach collection="eids" item="eid" separator="," open="(" close=")">
#{eid}
foreach>
delete>
@Test
public void deleteMoreByArray() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
DynamicSQLMapper mapper = sqlSession.getMapper(DynamicSQLMapper.class);
int result = mapper.deleteMoreByArray(new Integer[]{6, 7, 8, 9});
System.out.println(result);
}
<insert id="insertMoreByList">
insert into t_emp values
<foreach collection="emps" item="emp" separator=",">
(null,#{emp.empName},#{emp.age},#{emp.sex},#{emp.email},null)
foreach>
insert>
@Test
public void insertMoreByList() {
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
DynamicSQLMapper mapper = sqlSession.getMapper(DynamicSQLMapper.class);
Emp emp1 = new Emp(null,"a",1,"男","[email protected]",null);
Emp emp2 = new Emp(null,"b",1,"男","[email protected]",null);
Emp emp3 = new Emp(null,"c",1,"男","[email protected]",null);
List<Emp> emps = Arrays.asList(emp1, emp2, emp3);
int result = mapper.insertMoreByList(emps);
System.out.println(result);
}
标签<sql id="empColumns">eid,emp_name,age,sex,emailsql>
标签
<select id="getEmpByCondition" resultType="Emp">
select <include refid="empColumns">include> from t_emp
select>
- 不同的SqlSession对应不同的一级缓存
- 同一个SqlSession但是查询条件不同
- 同一个SqlSession两次查询期间执行了任何一次增删改操作
- 同一个SqlSession两次查询期间手动清空了缓存
- 在核心配置文件中,设置全局配置属性cacheEnabled=“true”,默认为true,不需要设置
- 在映射文件中设置标签
- 二级缓存必须在SqlSession关闭或提交之后有效
- 查询的数据所转换的实体类类型必须实现序列化的接口
<dependency>
<groupId>org.mybatis.cachesgroupId>
<artifactId>mybatis-ehcacheartifactId>
<version>1.2.1version>
dependency>
<dependency>
<groupId>ch.qos.logbackgroupId>
<artifactId>logback-classicartifactId>
<version>1.2.3version>
dependency>
jar包名称 | 作用 |
---|---|
mybatis-ehcache | Mybatis和EHCache的整合包 |
ehcache | EHCache核心包 |
slf4j-api | SLF4J日志门面包 |
logback-classic | 支持SLF4J门面接口的一个具体实现 |
ehcache.xml
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
<diskStore path="D:\atguigu\ehcache"/>
<defaultCache
maxElementsInMemory="1000"
maxElementsOnDisk="10000000"
eternal="false"
overflowToDisk="true"
timeToIdleSeconds="120"
timeToLiveSeconds="120"
diskExpiryThreadIntervalSeconds="120"
memoryStoreEvictionPolicy="LRU">
defaultCache>
ehcache>
<cache type="org.mybatis.caches.ehcache.EhcacheCache"/>
logback.xml
,名字固定,不可改变
<configuration debug="true">
<appender name="STDOUT"
class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>[%d{HH:mm:ss.SSS}] [%-5level] [%thread] [%logger] [%msg]%npattern>
encoder>
appender>
<root level="DEBUG">
<appender-ref ref="STDOUT" />
root>
<logger name="com.atguigu.crowd.mapper" level="DEBUG"/>
configuration>
属性名 | 是否必须 | 作用 |
---|---|---|
maxElementsInMemory | 是 | 在内存中缓存的element的最大数目 |
maxElementsOnDisk | 是 | 在磁盘上缓存的element的最大数目,若是0表示无穷大 |
eternal | 是 | 设定缓存的elements是否永远不过期。 如果为true,则缓存的数据始终有效, 如果为false那么还要根据timeToIdleSeconds、timeToLiveSeconds判断 |
overflowToDisk | 是 | 设定当内存缓存溢出的时候是否将过期的element缓存到磁盘上 |
timeToIdleSeconds | 否 | 当缓存在EhCache中的数据前后两次访问的时间超过timeToIdleSeconds的属性取值时, 这些数据便会删除,默认值是0,也就是可闲置时间无穷大 |
timeToLiveSeconds | 否 | 缓存element的有效生命期,默认是0.,也就是element存活时间无穷大 |
diskSpoolBufferSizeMB | 否 | DiskStore(磁盘缓存)的缓存区大小。默认是30MB。每个Cache都应该有自己的一个缓冲区 |
diskPersistent | 否 | 在VM重启的时候是否启用磁盘保存EhCache中的数据,默认是false |
diskExpiryThreadIntervalSeconds | 否 | 磁盘缓存的清理线程运行间隔,默认是120秒。每个120s, 相应的线程会进行一次EhCache中数据的清理工作 |
memoryStoreEvictionPolicy | 否 | 当内存缓存达到最大,有新的element加入的时候, 移除缓存中element的策略。 默认是LRU(最近最少使用),可选的有LFU(最不常使用)和FIFO(先进先出 |
<dependencies>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.5.9version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.13.2version>
<scope>testscope>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.27version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.mybatis.generatorgroupId>
<artifactId>mybatis-generator-maven-pluginartifactId>
<version>1.3.0version>
<dependencies>
<dependency>
<groupId>org.mybatis.generatorgroupId>
<artifactId>mybatis-generator-coreartifactId>
<version>1.3.2version>
dependency>
<dependency>
<groupId>com.mchangegroupId>
<artifactId>c3p0artifactId>
<version>0.9.2version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.27version>
dependency>
dependencies>
plugin>
plugins>
build>
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=""/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
dataSource>
environment>
environments>
<mappers>
<package name=""/>
mappers>
configuration>
generatorConfig.xml
DOCTYPE generatorConfiguration
PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
"http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
<context id="DB2Tables" targetRuntime="MyBatis3">
<jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
connectionURL="jdbc:mysql://localhost:3306/mybatis"
userId="root"
password="dy">
jdbcConnection>
<javaModelGenerator targetPackage="com.atguigu.mybatis.pojo" targetProject=".\src\main\java">
<property name="enableSubPackages" value="true" />
<property name="trimStrings" value="true" />
javaModelGenerator>
<sqlMapGenerator targetPackage="com.atguigu.mybatis.mapper"
targetProject=".\src\main\resources">
<property name="enableSubPackages" value="true" />
sqlMapGenerator>
<javaClientGenerator type="XMLMAPPER"
targetPackage="com.atguigu.mybatis.mapper" targetProject=".\src\main\java">
<property name="enableSubPackages" value="true" />
javaClientGenerator>
<table tableName="tb_brand" domainObjectName="Brand"/>
<table tableName="tb_user" domainObjectName="User"/>
context>
generatorConfiguration>
selectByExample
:按条件查询,需要传入一个example对象或者null;如果传入一个null,则表示没有条件,也就是查询所有数据example.createCriteria().xxx
:创建条件对象,通过andXXX方法为SQL添加查询添加,每个条件之间是and关系example.or().xxx
:将之前添加的条件通过or拼接其他条件@Test public void testMBG() throws IOException {
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
SqlSession sqlSession = sqlSessionFactory.openSession(true);
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
EmpExample example = new EmpExample();
//名字为张三,且年龄大于等于20
example.createCriteria().andEmpNameEqualTo("张三").andAgeGreaterThanOrEqualTo(20);
//或者did不为空
example.or().andDidIsNotNull();
List<Emp> emps = mapper.selectByExample(example);
emps.forEach(System.out::println);
}
updateByPrimaryKey
:通过主键进行数据修改,如果某一个值为null,也会将对应的字段改为nullmapper.updateByPrimaryKey(new Emp(1,"admin",22,null,"[email protected]",3));
updateByPrimaryKeySelective()
:通过主键进行选择性数据修改,如果某个值为null,则不修改这个字段mapper.updateByPrimaryKeySelective(new Emp(2,"admin2",22,null,"[email protected]",3));
<dependency>
<groupId>com.github.pagehelpergroupId>
<artifactId>pagehelperartifactId>
<version>5.2.0version>
dependency>
<plugins>
<plugin interceptor="com.github.pagehelper.PageInterceptor">plugin>
plugins>
PageHelper.startPage(int pageNum, int pageSize)
开启分页功能@Test
public void testPageHelper() throws IOException {
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
SqlSession sqlSession = sqlSessionFactory.openSession(true);
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
//访问第一页,每页四条数据
PageHelper.startPage(1,4);
List<Emp> emps = mapper.selectByExample(null);
emps.forEach(System.out::println);
}
@Test
public void testPageHelper() throws IOException {
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
SqlSession sqlSession = sqlSessionFactory.openSession(true);
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
//访问第一页,每页四条数据
Page<Object> page = PageHelper.startPage(1, 4);
List<Emp> emps = mapper.selectByExample(null);
//在查询到List集合后,打印分页数据
System.out.println(page);
}
分页相关数据:
Page{count=true, pageNum=1, pageSize=4, startRow=0, endRow=4, total=8, pages=2, reasonable=false, pageSizeZero=false}[Emp{eid=1, empName=‘admin’, age=22, sex=‘男’, email=‘[email protected]’, did=3}, Emp{eid=2, empName=‘admin2’, age=22, sex=‘男’, email=‘[email protected]’, did=3}, Emp{eid=3, empName=‘王五’, age=12, sex=‘女’, email=‘[email protected]’, did=3}, Emp{eid=4, empName=‘赵六’, age=32, sex=‘男’, email=‘[email protected]’, did=1}]
PageInfo pageInfo = new PageInfo<>(List list, intnavigatePages)
获取分页相关数据@Test
public void testPageHelper() throws IOException {
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
SqlSession sqlSession = sqlSessionFactory.openSession(true);
EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
PageHelper.startPage(1, 4);
List<Emp> emps = mapper.selectByExample(null);
PageInfo<Emp> page = new PageInfo<>(emps,5);
System.out.println(page);
}
分页相关数据:
PageInfo{
pageNum=1, pageSize=4, size=4, startRow=1, endRow=4, total=8, pages=2,
list=Page{count=true, pageNum=1, pageSize=4, startRow=0, endRow=4, total=8, pages=2, reasonable=false, pageSizeZero=false}[Emp{eid=1, empName=‘admin’, age=22, sex=‘男’, email=‘[email protected]’, did=3}, Emp{eid=2, empName=‘admin2’, age=22, sex=‘男’, email=‘[email protected]’, did=3}, Emp{eid=3, empName=‘王五’, age=12, sex=‘女’, email=‘[email protected]’, did=3}, Emp{eid=4, empName=‘赵六’, age=32, sex=‘男’, email=‘[email protected]’, did=1}],
prePage=0, nextPage=2, isFirstPage=true, isLastPage=false, hasPreviousPage=false, hasNextPage=true, navigatePages=5, navigateFirstPage=1, navigateLastPage=2, navigatepageNums=[1, 2]}
其中list中的数据等同于方法一中直接输出的page数据