Mybatis Plus入门 - 好文

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
 <context:property-placeholder
location="classpath:db.properties" ignore-unresolvable="true"/>  <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"/>   <property
name="typeAliasesPackage" value="cn.xm.jwxt.bean.*"/> <property
name="configuration" ref="mybatisConfig"/>  <property
name="globalConfig" ref="globalConfig"/> <property name="plugins"> <array>  <bean id="paginationInterceptor"class
="com.baomidou.mybatisplus.plugins.PaginationInterceptor"/>  <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> 
<bean id="globalConfig"class
="com.baomidou.mybatisplus.entity.GlobalConfiguration"> <property name="idType"
value="2"/> <property name="dbType" value="mysql"/> 
<property name="dbColumnUnderline" value="true"/> </bean> 
<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 ); }

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