Mybatis Plus入门
MyBatis Plus介绍
MyBatis Plus （简称MP）是国内人员开发的 MyBatis 增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。
特征
无侵入：Mybatis-Plus 在 Mybatis 的基础上进行扩展，只做增强不做改变，引入 Mybatis-Plus 不会对您现有的 Mybatis 构架产生任何影响，而且 MP 支持所有 Mybatis 原生的特性
依赖少：仅仅依赖 Mybatis 以及 Mybatis-Spring
损耗小：启动即会自动注入基本CURD，性能基本无损耗，直接面向对象操作
预防Sql注入：内置Sql注入剥离器，有效预防Sql注入攻击
通用CRUD操作：内置通用 Mapper、通用 Service，仅仅通过少量配置即可实现单表大部分 CRUD 操作，更有强大的条件构造器，满足各类使用需求
多种主键策略：支持多达4种主键策略（内含分布式唯一ID生成器），可自由配置，完美解决主键问题
框架结构
Mybatis Plus使用
1.导入依赖
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus</artifactId>
<version>2.0.1</version>
</dependency>
2.MP整合的配置
<!-- 0.连接池属性设置读取指定的properties文件 -->
<context:property-placeholder location="classpath:db.properties" ignore-unresolvable="true"/>
<!-- 1.将连接池放入spring容器 -->
<bean name="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="jdbcUrl" value="${jdbc.url}"></property>
<property name="driverClass" value="${jdbc.driver}"></property>
<property name="user" value="${jdbc.username}"></property>
<property name="password" value="${jdbc.password}"></property>
</bean>
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.spring.MybatisSqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<!-- 配置实体扫描路径，多个package可以用分号; 逗号, 分隔， 支持通配符*-->
<!-- com.a.b.entity;com.a.c.entity;com.d.*.entity-->
<property name="typeAliasesPackage" value="cn.xm.jwxt.bean.*"/>
<property name="configuration" ref="mybatisConfig"/>
<!-- MP 全局配置注入 -->
<property name="globalConfig" ref="globalConfig"/>
<property name="plugins">
<array>
<!-- 分页插件配置 -->
<bean id="paginationInterceptor"
class="com.baomidou.mybatisplus.plugins.PaginationInterceptor"/>
<!-- 性能拦截器，兼打印sql，不建议生产环境配置-->
<bean id="performanceInterceptor"
class="com.baomidou.mybatisplus.plugins.PerformanceInterceptor"/>
</array>
</property>
</bean>
<bean id="mybatisConfig" class="com.baomidou.mybatisplus.MybatisConfiguration">
<property name="mapUnderscoreToCamelCase" value="true"/>
</bean>
<!-- 定义 MP 全局策略 -->
<bean id="globalConfig" class="com.baomidou.mybatisplus.entity.GlobalConfiguration">
<property name="idType" value="2"/>
<property name="dbType" value="mysql"/>
<!-- 全局表为下划线命名设置 true -->
<property name="dbColumnUnderline" value="true"/>
</bean>
<!-- 配置mybatis 扫描mapper接口的路径, 相当于注解@MapperScan，@MapperScan("com.baomidou.mybatisplus.test.h2.entity.mapper")-->
<bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="cn.xm.jwxt.mapper"/>
</bean>
3.实体
@TableName(value="employee")
public class Employee { private Integer id ; private String lastName; private String email ; private Integer gender; private Integer age ; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public Integer getGender() { return gender; } public void setGender(Integer gender) { this.gender = gender; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + ", age=" + age + "]"; } }
4.mapper 接口
public interface EmployeeMapper extends BaseMapper<Employee> {}
5.新增
@Test public void testCommonInsert() { //初始化Employee对象 Employee employee = new Employee(); employee.setLastName("MP"); employee.setEmail("mp@atguigu.com"); employee.setGender(1); //insert方法在插入时，会根据实体类的每个属性进行非空判断，只有非空的属性对应的字段才会出现到SQL语句中 Integer result = employeeMapper.insert(employee); System.out.println("result: " + result ); //insertAllColumn方法在插入时，不管属性是否非空， 属性所对应的字段都会出现到SQL语句中. Integer result1 = employeeMapper.insertAllColumn(employee); System.out.println("result: " + result1 ); //获取当前数据在数据库中的主键值 Integer key = employee.getId(); System.out.println("key:" + key ); }
6.修改
@Test public void testCommonUpdate() { //初始化修改对象 Employee employee = new Employee(); employee.setId(7); employee.setLastName("王五"); employee.setEmail("xz@sina.com"); employee.setGender(0); //updateById方法在修改时，会根据实体类的每个属性进行非空判断，只有非空的属性对应的字段才会出现到SQL语句中 Integer result = employeeMapper.updateById(employee); System.out.println("result: " + result ); //updateAllColumnById方法在修改时，不管属性是否非空， 属性所对应的字段都会出现到SQL语句中. Integer result1 = employeeMapper.updateAllColumnById(employee); System.out.println("result: " + result1 ); }
7.查询
@Test public void testCommonSelect() { //1. 通过id查询 Employee employee = employeeMapper.selectById(7); System.out.println(employee); //2. 通过多个列进行查询。selectOne查询结果只能是一条，否则报错 Employee employee1 = new Employee(); employee.setLastName("王五"); employee.setGender(0); Employee result = employeeMapper.selectOne(employee1); System.out.println("result: " +result ); //3. 通过多个id进行查询 List<Integer> idList = new ArrayList<>(); idList.add(4); idList.add(5); idList.add(6); idList.add(7); List<Employee> emps = employeeMapper.selectBatchIds(idList); System.out.println(emps); //4. 通过Map封装条件查询。map中的key是数据库中字段名 Map<String,Object> columnMap = new HashMap<>(); columnMap.put("last_name", "Tom"); columnMap.put("gender", 1); List<Employee> emps1 = employeeMapper.selectByMap(columnMap); System.out.println(emps1); //5. 分页查询 List<Employee> emps2 = employeeMapper.selectPage(new Page<>(3, 2), null); System.out.println(emps2); }
8.删除
@Test public void testCommonDelete() { //1 .根据id进行删除 Integer result = employeeMapper.deleteById(13); System.out.println("result: " + result ); //2. 根据条件进行删除 Map<String,Object> columnMap = new HashMap<>(); columnMap.put("last_name", "MP"); columnMap.put("email", "mp@atguigu.com"); Integer result1 = employeeMapper.deleteByMap(columnMap); System.out.println("result: " + result1 ); //3. 批量删除 List<Integer> idList = new ArrayList<>(); idList.add(3); idList.add(4); idList.add(5); Integer result2 = employeeMapper.deleteBatchIds(idList); System.out.println("result: " + result2 ); }
