MyBatis简单入门
文章目录
-
- 快速入
- Mapper代理开发
-
- 具体步骤
-
- 使用mapper代理中的包扫描
- 查询
-
- 字段名称不一致问题
-
- 方法一：对SQL语句起别名
- 方法二： 采用resultMap映射
- 条件查询
-
- 单条件查询
-
- SQL中特殊字符的处理
- 多条件查询
-
- 方式一：散装参数
- 方式二：对象参数
- 方式三：map集合参数
- 动态多条件查询
- 单条件动态查询
- 添加
- 更新
-
- 修改全部字段
- 修改动态字段
- 删除
-
- 根据指定值删除
- 动态批量删除
参考
快速入
一些pom.xml依赖
<dependencies>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.11version>
<scope>testscope>
dependency>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.5.13version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.30version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-apiartifactId>
<version>1.7.20version>
dependency>
<dependency>
<groupId>ch.qos.logbackgroupId>
<artifactId>logback-classicartifactId>
<version>1.2.3version>
dependency>
<dependency>
<groupId>ch.qos.logbackgroupId>
<artifactId>logback-coreartifactId>
<version>1.4.8version>
dependency>
dependencies>
mybatis-config.xml配置文件
注意，这里由于xml语法，&是非法的，将其转换成&
DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://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.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/jdbc?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&useOldAliasMetadataBehavior=true&useServerPrepStmts=true"/>
<property name="username" value="root"/>
<property name="password" value="5508769123"/>
dataSource>
environment>
<environment id="test">
<transactionManager type="JDBCC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/jdbcc?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&useOldAliasMetadataBehavior=true&useServerPrepStmts=true"/>
<property name="username" value="roottt"/>
<property name="password" value="114514"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="StudentMapper.xml"/>
mappers>
configuration>
注意：这里的加载sql映射文件：有下面两种方法：1.挨个挨个写；2.包扫描
-
挨个挨个写
就是上面的写法，不过当有多个XXXMapper时需要将所有的都按照这个方法写出来
-
包扫描见下面的mapper代理开发部分
编写SQL映射文件
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="test">
<select id="selectAll" resultType="pojo.Student">
select * from student;
select>
mapper>
使用相对路径
一些测试类
Student.java
package pojo;
public class Student {
private Integer id;
private String name;
private String sex;
private Integer 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 String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + "]";
}
}
MyBasitDemo.java
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 pojo.Student;
public class MyBasitDemo {
public static void main(String[] args) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.执行sql
List<Student> users = sqlSession.selectList("test.selectAll");
System.out.println(users);
// 4.释放资源
sqlSession.close();
}
}
注意
List<Student> users = sqlSession.selectList("test.selectAll");
中的test.selectAll为StudentMapper.xml 中的指定的部分namespace.select id
Mapper代理开发
具体步骤
对于第一步，先了解maven打包之后的框架。
可以发现，在源文件中StudentMapper.xml是放在resources文件夹中，但是打包成target之后StudentMapper.xml就没有resource目录了，因此若要想StudentMapper.java打包之后与StudentMapper.xml同一个同一文件夹下，可以将源文件中StudentMaper.xml放在与StudentMapper.java同一个结构之下(不是复制放在一起而是新创路径)，这样打包之后StudentMapper.xml将会被自动塞进与StudentMapper.java同一文件夹。如下：
- 定义与SQL映射文件同名的Mapper接口，并且将Mapper接口和SQL映射文件放置同一目录之下
因此，配置文件mybatis-config.xml也要随之改变
DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://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.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/jdbc?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&useOldAliasMetadataBehavior=true&useServerPrepStmts=true"/>
<property name="username" value="root"/>
<property name="password" value="5508769123"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="mapper\StudentMapper.xml"/>
mappers>
configuration>
StudentMapper.java
package mapper;
import java.util.List;
import pojo.Student;
public interface StudentMapper {
List<Student> selectAll();
}
-
设置SQL映射文件的namespace属性为Mapper接口全限定名称，如下面的mapper.StudentMapper
StudentMapper.xmlDOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="mapper.StudentMapper"> <select id="selectAll" resultType="pojo.Student"> select * from student; select> mapper> -
在Mapper接口中定义方法，方法名就是SQL映射文件中sql语句的id，并保持参数类型和返回类型一致
StudentMapper.javapackage mapper; import java.util.List; import pojo.Student; public interface StudentMapper { List<Student> selectAll(); }
使用mapper代理中的包扫描
如果Mapper接口名称和SQL映射文件名称相同，并且放在同一目录下，则可以使用包扫描的方式简化SQL映射文件的加载
上述代理中，有一个StudentMapper文件就要在mybatis-config.xml添加一行映射
<mapper resource="mapper\StudentMapper.xml"/>
这样当映射多了的时候添加起来很麻烦，就干脆直接添加映射文件的文件夹，到时候直接扫描该文件夹下的映射文件
mybatis-config.xml修改如下：
DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://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.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/jdbc?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&useOldAliasMetadataBehavior=true&useServerPrepStmts=true"/>
<property name="username" value="root"/>
<property name="password" value="5508769123"/>
dataSource>
environment>
<mappers>
<package name="mapper"/>
mappers>
configuration>
-
测试编码：
MyBasitDemo.javaimport java.io.IOException; import java.io.InputStream; import java.util.List; 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 mapper.StudentMapper; import pojo.Student; // mapper代理开发 public class MyBasitDemo { public static void main(String[] args) throws IOException { // 1.加载mybatis的核心配置文件，获取SqlSessionFactory String resource = "config\\anyshare\\mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); // 2.获取SqlSession对象，用它来执行sql SqlSession sqlSession = sqlSessionFactory.openSession(); // 3.获取StudentMapper接口的代理对象 StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class); //4.执行 List<Student> students = studentMapper.selectAll(); System.out.println(students); // 5.释放资源 sqlSession.close(); } }
查询
字段名称不一致问题
由于查询时要求类中的成员字段(Java采用驼峰命名)要与数据库中的标段相同(采用下划线)，因此若不大同则会出现查询结果某成员为null的情况
数据库：
Java：
可以发现，nameCh，nameEn均与数据库中字段不一致
查询方法采用上面Mapper代理中的MyBasitDemo.java类方法
将会得到下面的结果：
方法一：对SQL语句起别名
对StudentMapper.xml文件中的SQL语句中不对应的列名采用起与StudentMapper.java中一致的别名。
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<sql id = "student_column">
id,name_ch as nameCh,sex,age,name_en as nameEn
sql>
<select id="selectAll" resultType="pojo.Student">
select
<include refid = "student_column" />
from student;
select>
mapper>
再次执行查询语句：
方法二： 采用resultMap映射
由sql相关知识可知，若要取别名则需要列出所有的列名(尽管不需要)，这样是十分繁琐的。因此可以采用更为灵活的方法来映射
对StudentMapper.xml进行修改
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectAll" resultMap = "studentResultMap">
select * from student;
select>
mapper>
条件查询
单条件查询
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectById" parameterType = "int" resultMap = "studentResultMap">
select * from student where id = #{id};
select>
mapper>
在StudentMapper.java中添加相应的接口方法Student selectById(int id);
package mapper;
import java.util.List;
import pojo.Student;
public interface StudentMapper {
List<Student> selectAll();
Student selectById(int id);
}
编写测试代码 MyBasitDemo.java
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo {
public static void main(String[] args) throws IOException {
// selectAll();
selectById(2);
}
public static void selectAll() throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
List<Student> students = studentMapper.selectAll();
System.out.println(students);
// 4.释放资源
sqlSession.close();
}
public static void selectById(int id) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
Student student = studentMapper.selectById(id);
System.out.println(student);
// 5.释放资源
sqlSession.close();
}
}
SQL中特殊字符的处理
在xml与语句中<为标记符号，因此例如语句 select * from student where id < #{id}; 是非法的。
处理方法：1.将非法符号转译；2.使用CDATA空间
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectAll" resultMap = "studentResultMap">
select * from student;
select>
<select id = "selectById" parameterType = "int" resultMap = "studentResultMap">
select * from student where id
2;
select>
mapper>
多条件查询
多条件查询
参数接受
1.散装参数：如果方法中有多个参数，需要使用@Param(“SQL参数占位符名称”)
2.对象参数：对象的属性名称要和参数占位符名称一致
3.map集合参数：键的名称要和参数占位符名称一致
三种方式，StudentMapper.xml均不用修改
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectByConditions" resultMap = "studentResultMap">
select * from student where age < #{age}
and name_en like #{nameEn};
select>
mapper>
方式一：散装参数
StudentMapper.java：
package mapper;
import java.util.List;
import org.apache.ibatis.annotations.Param;
import pojo.Student;
public interface StudentMapper {
// 1.散装参数
// 当存在多个参数时，需要使用Param来区分传给xml的参数
List<Student> selectByConditions(@Param("age") int age, @Param("nameEn") String nameEn);
}
MyBasitDemo.java：
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
selectByConditions(25, "a");
}
// 1.散装参数
public static void selectByConditions(int age,String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 参数处理
nameEn = "%" + nameEn + "%";
List<Student> students = studentMapper.selectByConditions(age, nameEn);
System.out.println(students);
// 5.释放资源
sqlSession.close();
}
}
方式二：对象参数
StudentMapper.java：
package mapper;
import java.util.List;
import pojo.Student;
public interface StudentMapper {
// 2.对象参数
List<Student> selectByConditions(Student student);nameEn);
}
MyBasitDemo.java：
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
selectByConditions(25, "a");
}
// 2.对象参数
public static void selectByConditions(int age, String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 参数处理
nameEn = "%" + nameEn + "%";
// 封装对象
Student student = new Student();
student.setAge(age);
student.setNameEn(nameEn);
List<Student> students = studentMapper.selectByConditions(student);
System.out.println(students);
// 5.释放资源
sqlSession.close();
}
}
方式三：map集合参数
StudentMapper.java：
package mapper;
import java.util.List;
import java.util.Map;
import pojo.Student;
public interface StudentMapper {
// 3.map集合参数
List<Student> selectByConditions(Map map);
}
MyBasitDemo.java：
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
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 mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
selectByConditions(25, "a");
}
// 3.map集合参数
public static void selectByConditions(int age,String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 参数处理
nameEn = "%" + nameEn + "%";
// 封装对象
HashMap<String, Object> hashMap = new HashMap<>();
hashMap.put("age", age);
hashMap.put("nameEn", nameEn);
List<Student> students = studentMapper.selectByConditions(hashMap);
System.out.println(students);
// 5.释放资源
sqlSession.close();
}
}
动态多条件查询
在上面使用的条件查询语句存在问题，当三种方式中MyBasitDemo.java中的selectByConditions方法参数age、nameEn没有值即为null时SQL语句将查询不出结果（正常情况应该是返回该表的所有数据）。
使用逻辑判断：
StudentMapper.xml：
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectByConditions" resultMap = "studentResultMap">
select * from student where
<if test = "age != null">
age < #{age}
if>
<if test = "nameEn != null and nameEn !=''">
and name_en like #{nameEn};
if>
select>
mapper>
-
当age !=null且nameEn==null时，SQL语句为：
select * from student where age < age;
但是这样也同样存在问题：不符合SQL规范
-
当agenull且nameEnnull时，SQL语句为：
select * from student where -
当age==null且nameEn!=null时，SQL语句为：
select * from student where and name_en like nameEn;
解决方式：
一、用恒等式使其达到语法要求 1 = 1 ,让所有条件格式都一样
<select id = "selectByConditionsDynamic" resultMap = "studentResultMap">
select * from student where 1 = 1
<if test = "age != null">
and age < #{age}
if>
<if test = "nameEn != null and nameEn !=''">
and name_en like #{nameEn};
if>
select>
二、用 代替where
<select id = "selectByConditionsDynamic" resultMap = "studentResultMap">
select * from student
<where>
<if test = "age != null">
and age < #{age}
if>
<if test = "nameEn != null and nameEn !=''">
and name_en like #{nameEn};
if>
where>
select>
单条件动态查询
从多个条件中选择一个
与上面动态多条件查询的不同是：if条件可以满足多个并执行相应SQL语句，而单条件只能执行一个
- choose(when,otherwise)：选择，类似于Java中switch语句
StudentMapper.java
package mapper;
import java.util.List;
import org.apache.ibatis.annotations.Param;
import pojo.Student;
public interface StudentMapper {
// 单条件动态查询
List<Student> selectByConditionDynamic(Student student);
}
MyBasitDemo.java
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
selectByConditionDynamic("小","a");
}
public static void selectByConditionDynamic(String nameCh,String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 参数处理
nameEn = "%" + nameEn + "%";
nameCh = "%" + nameCh + "%";
// 封装对象
Student student = new Student();
student.setNameCh(null);
student.setNameEn(null);
List<Student> students = studentMapper.selectByConditionDynamic(student);
System.out.println(students);
// 5.释放资源
sqlSession.close();
}
}
StudentMapper.xml可以写成两种
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectAll" resultMap = "studentResultMap">
select * from student;
select>
<select id = "selectByConditionDynamic" resultMap = "studentResultMap">
select * from student
<where>
<choose>
<when test = "nameCh != null">
name_ch like #{nameCh};
when>
<when test = "nameEn != null">
name_en like #{nameEn};
when>
choose>
where>
select>
mapper>
或者
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<resultMap id = "studentResultMap" type = "pojo.Student">
<result column = "name_ch" property = "nameCh"/>
<result column = "name_en" property = "nameEn"/>
resultMap>
<select id = "selectByConditionDynamic" resultMap = "studentResultMap">
select * from student
<where>
<choose>
<when test = "nameCh != null">
name_ch like #{nameCh};
when>
<when test = "nameEn != null">
name_en like #{nameEn};
when>
choose>
where>
select>
mapper>
添加
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<insert id = "add" useGeneratedKeys= "true" keyProperty = "id">
insert into student(name_ch,sex,age,name_en)
values(#{nameCh},#{sex},#{age},#{nameEn});
insert>
mapper>
StudentMapper.java
package mapper;
import pojo.Student;
public interface StudentMapper {
// 添加
void add(Student student);
}
MyBasitDemo2.java
import java.io.IOException;
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;
import mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
add("小李","男",16,"xiaoli");
}
public static void add(String nameCh,String sex,int age,String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 封装对象
Student student = new Student();
student.setNameCh(nameCh);
student.setSex(sex);
student.setAge(age);
student.setNameEn(nameEn);
// 4.执行
studentMapper.add(student);
// 提交事务
sqlSession.commit();
//获取主键
System.out.println(student.getId());
// 5.释放资源
sqlSession.close();
}
}
更新
修改全部字段
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<update id = "update">
update student set
name_ch = #{nameCh},
name_en = #{nameEn},
sex = #{sex},
age = #{age}
where id = #{id};
update>
mapper>
StudentMapper.java
package mapper;
import pojo.Student;
public interface StudentMapper {
// 修改更新
int update(Student student);
}
MyBasitDemo.java
import java.io.IOException;
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;
import mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo {
public static void main(String[] args) throws IOException {
update(10,"大红","男",25,"dahong");
}
public static void update(int id,String nameCh,String sex,int age,String nameEn) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 封装对象
Student student = new Student();
student.setId(id);
student.setNameCh(nameCh);
student.setSex(sex);
student.setAge(age);
student.setNameEn(nameEn);
// 4.执行
// 获取影响行数看是否成功更新
int count = studentMapper.update(student);
System.out.println(count);
// 提交事务
sqlSession.commit();
// 5.释放资源
sqlSession.close();
}
}
修改动态字段
当上面的修改全部字段中的传入参数存在null时，SQL语句将会报错，因此我们需要做到：当传入的某个参数为null时，需要在SQL语句中将其忽视。这就要在xml中使用set标签来代替set。
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<update id = "update">
update student
<set>
<if test = "nameCh != null and nameCh != ''">
name_ch = #{nameCh},
if>
<if test = "nameEn != null and nameEn != ''">
name_en = #{nameEn},
if>
<if test = "sex != null and sex != ''">
sex = #{sex},
if>
<if test = "age != null">
age = #{age}
if>
set>
where id = #{id}
update>
mapper>
StudentMapper.java接口声明 与MyBasitDemo.java方法实现无需改变
删除
根据指定值删除
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<delete id = "deleteById">
delete from student where id = #{id};
delete>
mapper>
StudentMapper.java
package mapper;
import org.apache.ibatis.annotations.Param;
import pojo.Student;
public interface StudentMapper {
// 根据id删除
int deleteById(int id);
}
MyBasitDemo.java
import java.io.IOException;
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;
import mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
deleteById(1);
}
public static void deleteById(int id) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 获取影响行数看是否成功删除
int count = studentMapper.deleteById(id);
System.out.println(count);
// 提交事务
sqlSession.commit();
// 5.释放资源
sqlSession.close();
}
}
动态批量删除
相当于一次性执行多次上面的根据指定值删除
StudentMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.StudentMapper">
<delete id = "deleteByIds">
delete from student where id in (
<foreach collection = "ids" item = "id" separator=",">
#{id}
foreach>
);
delete>
mapper>
StudentMapper.java
package mapper;
import org.apache.ibatis.annotations.Param;
import pojo.Student;
public interface StudentMapper {
// 批量删除
int deleteByIds(@Param("ids") int[] ids);
}
MyBasitDemo.java
import java.io.IOException;
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;
import mapper.StudentMapper;
import pojo.Student;
// mapper代理开发
public class MyBasitDemo2 {
public static void main(String[] args) throws IOException {
deleteByIds(new int[]{1,2});
}
public static void deleteByIds(int[] ids) throws IOException {
// 1.加载mybatis的核心配置文件，获取SqlSessionFactory
String resource = "config\\anyshare\\mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.获取SqlSession对象，用它来执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取StudentMapper接口的代理对象
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
// 4.执行
// 获取影响行数看是否成功删除
int count = studentMapper.deleteByIds(ids);
System.out.println(count);
// 提交事务
sqlSession.commit();
// 5.释放资源
sqlSession.close();
}
}