【官网快速上手地址】
https://mp.baomidou.com/guide/quick-start.html#%E5%88%9D%E5%A7%8B%E5%8C%96%E5%B7%A5%E7%A8%8B
创建一个空的数据库，并插入user表和数据：
DROP TABLE IF EXISTS user; CREATE TABLE user ( id BIGINT(20) NOT NULL COMMENT '主键ID', name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名', age INT(11) NULL DEFAULT NULL COMMENT '年龄', email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱', PRIMARY KEY (id) ); DELETE FROM user; INSERT INTO user (id, name, age, email) VALUES (1, 'Jone', 18, 'test1@baomidou.com'), (2, 'Jack', 20, 'test2@baomidou.com'), (3, 'Tom', 28, 'test3@baomidou.com'), (4, 'Sandy', 21, 'test4@baomidou.com'), (5, 'Billie', 24, 'test5@baomidou.com');
然后使用IDEA创建SpringBoot项目，不需要点击任何工具选项：
进入项目导入pom坐标：
<!-- JDBC --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency> <!-- lombok --> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </dependency> <!-- mybatis-plus --> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.3.2</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>
【application.properties】
配置连接参数：
spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver spring.datasource.url = jdbc:mysql://49.234.116.100:3306/mybatis_plus?serverTimezone=GMT spring.datasource.username = root spring.datasource.password = 123456
编写实体类：
@Data @AllArgsConstructor @NoArgsConstructor public class User { private Integer id; private String name; private Integer age; private String email; }
编写User的Mapper接口，使用Mybatis-Plus，将接口继承BaseMapper
public interface UserMapper extends BaseMapper<User> { }
【回顾我的阶段一项目，当时就这么写过一个基本的BaseDao接口...】
CRUD的代码已经由mybatis-plus帮助我们完成了
BaseMapper接口的源码：
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package com.baomidou.mybatisplus.core.mapper; import com.baomidou.mybatisplus.core.conditions.Wrapper; import com.baomidou.mybatisplus.core.metadata.IPage; import java.io.Serializable; import java.util.Collection; import java.util.List; import java.util.Map; import org.apache.ibatis.annotations.Param; public interface BaseMapper<T> extends Mapper<T> { int insert(T entity); int deleteById(Serializable id); int deleteByMap(@Param("cm") Map<String, Object> columnMap); int delete(@Param("ew") Wrapper<T> wrapper); int deleteBatchIds(@Param("coll") Collection<? extends Serializable> idList); int updateById(@Param("et") T entity); int update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper); T selectById(Serializable id); List<T> selectBatchIds(@Param("coll") Collection<? extends Serializable> idList); List<T> selectByMap(@Param("cm") Map<String, Object> columnMap); T selectOne(@Param("ew") Wrapper<T> queryWrapper); Integer selectCount(@Param("ew") Wrapper<T> queryWrapper); List<T> selectList(@Param("ew") Wrapper<T> queryWrapper); List<Map<String, Object>> selectMaps(@Param("ew") Wrapper<T> queryWrapper); List<Object> selectObjs(@Param("ew") Wrapper<T> queryWrapper); <E extends IPage<T>> E selectPage(E page, @Param("ew") Wrapper<T> queryWrapper); <E extends IPage<Map<String, Object>>> E selectMapsPage(E page, @Param("ew") Wrapper<T> queryWrapper); }
别忘了加持久层注解
在Main方法的类上面添加Mapper扫描注解
测试类：
@SpringBootTest class MybatisPlusApplicationTests { @Autowired // 自动装配 private UserMapper userMapper; @Test void contextLoads() { // wrapper 是一个封装查询条件的对象，如果不需要条件不就是null List<User> userList = userMapper.selectList(null); // lambda表达式 userList.forEach(System.out::print); } }
执行结果：
11:02:18.166 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating CacheAwareContextLoaderDelegate from class [org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate] 11:02:18.185 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating BootstrapContext using constructor [public org.springframework.test.context.support.DefaultBootstrapContext(java.lang.Class,org.springframework.test.context.CacheAwareContextLoaderDelegate)] 11:02:18.231 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating TestContextBootstrapper for test class [cn.echo42.MybatisPlusApplicationTests] from class [org.springframework.boot.test.context.SpringBootTestContextBootstrapper] 11:02:18.257 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Neither @ContextConfiguration nor @ContextHierarchy found for test class [cn.echo42.MybatisPlusApplicationTests], using SpringBootContextLoader 11:02:18.263 [main] DEBUG org.springframework.test.context.support.AbstractContextLoader - Did not detect default resource location for test class [cn.echo42.MybatisPlusApplicationTests]: class path resource [cn/echo42/MybatisPlusApplicationTests-context.xml] does not exist 11:02:18.263 [main] DEBUG org.springframework.test.context.support.AbstractContextLoader - Did not detect default resource location for test class [cn.echo42.MybatisPlusApplicationTests]: class path resource [cn/echo42/MybatisPlusApplicationTestsContext.groovy] does not exist 11:02:18.264 [main] INFO org.springframework.test.context.support.AbstractContextLoader - Could not detect default resource locations for test class [cn.echo42.MybatisPlusApplicationTests]: no resource found for suffixes {-context.xml, Context.groovy}. 11:02:18.265 [main] INFO org.springframework.test.context.support.AnnotationConfigContextLoaderUtils - Could not detect default configuration classes for test class [cn.echo42.MybatisPlusApplicationTests]: MybatisPlusApplicationTests does not declare any static, non-private, non-final, nested classes annotated with @Configuration. 11:02:18.329 [main] DEBUG org.springframework.test.context.support.ActiveProfilesUtils - Could not find an 'annotation declaring class' for annotation type [org.springframework.test.context.ActiveProfiles] and class [cn.echo42.MybatisPlusApplicationTests] 11:02:18.456 [main] DEBUG org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider - Identified candidate component class: file [C:UsersUser-DaiIdeaProjectsMybatis-Plus argetclassescnecho42MybatisPlusApplication.class] 11:02:18.457 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Found @SpringBootConfiguration cn.echo42.MybatisPlusApplication for test class cn.echo42.MybatisPlusApplicationTests 11:02:18.630 [main] DEBUG org.springframework.boot.test.context.SpringBootTestContextBootstrapper - @TestExecutionListeners is not present for class [cn.echo42.MybatisPlusApplicationTests]: using defaults. 11:02:18.631 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener, org.springframework.boot.test.autoconfigure.restdocs.RestDocsTestExecutionListener, org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerResetTestExecutionListener, org.springframework.boot.test.autoconfigure.web.servlet.MockMvcPrintOnlyOnFailureTestExecutionListener, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverTestExecutionListener, org.springframework.boot.test.autoconfigure.webservices.client.MockWebServiceServerTestExecutionListener, org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener, org.springframework.test.context.event.EventPublishingTestExecutionListener] 11:02:18.660 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@437da279, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@23c30a20, org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener@1e1a0406, org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener@3cebbb30, org.springframework.test.context.support.DirtiesContextTestExecutionListener@12aba8be, org.springframework.test.context.transaction.TransactionalTestExecutionListener@290222c1, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@67f639d3, org.springframework.test.context.event.EventPublishingTestExecutionListener@6253c26, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener@49049a04, org.springframework.boot.test.autoconfigure.restdocs.RestDocsTestExecutionListener@71a8adcf, org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerResetTestExecutionListener@27462a88, org.springframework.boot.test.autoconfigure.web.servlet.MockMvcPrintOnlyOnFailureTestExecutionListener@82de64a, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverTestExecutionListener@659499f1, org.springframework.boot.test.autoconfigure.webservices.client.MockWebServiceServerTestExecutionListener@51e69659] 11:02:18.667 [main] DEBUG org.springframework.test.context.support.AbstractDirtiesContextTestExecutionListener - Before test class: context [DefaultTestContext@d9345cd testClass = MybatisPlusApplicationTests, testInstance = [null], testMethod = [null], testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@2d710f1a testClass = MybatisPlusApplicationTests, locations = '{}', classes = '{class cn.echo42.MybatisPlusApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@1f0f1111, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@6e0dec4a, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@47d90b9e, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@3d680b5a, org.springframework.boot.test.context.SpringBootTestArgs@1], resourceBasePath = 'src/main/webapp', contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.web.ServletTestExecutionListener.activateListener' -> true]], class annotated with @DirtiesContext [false] with mode [null]. 11:02:18.725 [main] DEBUG org.springframework.test.context.support.TestPropertySourceUtils - Adding inlined properties to environment: {spring.jmx.enabled=false, org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true} . ____ _ __ _ _ /\ / ___'_ __ _ _(_)_ __ __ _ ( ( )\___ | '_ | '_| | '_ / _` | \/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.3.1.RELEASE) 2020-07-20 11:02:19.217 INFO 17456 --- [ main] cn.echo42.MybatisPlusApplicationTests : Starting MybatisPlusApplicationTests on DESKTOP-SDT4NG3 with PID 17456 (started by User-Dai in C:UsersUser-DaiIdeaProjectsMybatis-Plus) 2020-07-20 11:02:19.220 INFO 17456 --- [ main] cn.echo42.MybatisPlusApplicationTests : No active profile set, falling back to default profiles: default 2020-07-20 11:02:21.126 INFO 17456 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor' _ _ |_ _ _|_. ___ _ | _ | | |/|_)(_| | |_ |_)||_|_ / | 3.3.2 2020-07-20 11:02:22.667 INFO 17456 --- [ main] cn.echo42.MybatisPlusApplicationTests : Started MybatisPlusApplicationTests in 3.924 seconds (JVM running for 5.415) 2020-07-20 11:02:23.043 INFO 17456 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting... 2020-07-20 11:02:26.071 INFO 17456 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed. User(id=1, name=Jone, age=18, email=test1@baomidou.com)User(id=2, name=Jack, age=20, email=test2@baomidou.com)User(id=3, name=Tom, age=28, email=test3@baomidou.com)User(id=4, name=Sandy, age=21, email=test4@baomidou.com)User(id=5, name=Billie, age=24, email=test5@baomidou.com) 2020-07-20 11:02:26.215 INFO 17456 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated... 2020-07-20 11:02:26.472 INFO 17456 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed. 2020-07-20 11:02:26.473 INFO 17456 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor' Process finished with exit code 0
可以看到这里控制台的输出是没有打印SQL执行的，
所以我们需要配置日志输出
【application.properties】
# 日志配置
mybatis-plus.configuration.log-impl = org.apache.ibatis.logging.stdout.StdOutImpl
二次执行：
Creating a new SqlSession SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1687eb01] was not registered for synchronization because synchronization is not active 2020-07-20 11:07:10.780 INFO 25940 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting... 2020-07-20 11:07:12.318 INFO 25940 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed. JDBC Connection [HikariProxyConnection@1674550752 wrapping com.mysql.cj.jdbc.ConnectionImpl@594d9f07] will not be managed by Spring ==> Preparing: SELECT id,name,age,email FROM user ==> Parameters: <== Columns: id, name, age, email <== Row: 1, Jone, 18, test1@baomidou.com <== Row: 2, Jack, 20, test2@baomidou.com <== Row: 3, Tom, 28, test3@baomidou.com <== Row: 4, Sandy, 21, test4@baomidou.com <== Row: 5, Billie, 24, test5@baomidou.com <== Total: 5 Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1687eb01] User(id=1, name=Jone, age=18, email=test1@baomidou.com)User(id=2, name=Jack, age=20, email=test2@baomidou.com)User(id=3, name=Tom, age=28, email=test3@baomidou.com)User(id=4, name=Sandy, age=21, email=test4@baomidou.com)User(id=5, name=Billie, age=24, email=test5@baomidou.com) 2020-07-20 11:07:12.506 INFO 25940 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated... 2020-07-20 11:07:12.891 INFO 25940 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed. 2020-07-20 11:07:12.892 INFO 25940 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor' Process finished with exit code 0
【CRUD基操】
执行插入测试：
@Test void insertUser() { int insert = userMapper.insert( new User( null, "啊啊啊", 22, "1791255334@qq.com" ) ); }
插入失败：
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class cn.echo42.pojo.User' with value '1285049463613612034' Cause: java.lang.IllegalArgumentException: argument type mismatch
最终原因是因为类型不匹配：
java.lang.IllegalArgumentException: argument type mismatch
在我们User对象id属性设置null进行插入时，mybatis会自动生成一个UID插入
但是显然超出Integer的范围，所以改用Long试试
private Long id;
测试结果果然成功：
Creating a new SqlSession SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@237f7970] was not registered for synchronization because synchronization is not active 2020-07-20 11:16:52.830 INFO 19932 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting... 2020-07-20 11:16:54.222 INFO 19932 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed. JDBC Connection [HikariProxyConnection@441867003 wrapping com.mysql.cj.jdbc.ConnectionImpl@2fd64b11] will not be managed by Spring ==> Preparing: INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? ) ==> Parameters: 1285051019587166210(Long), 啊啊啊(String), 22(Integer), 1791255334@qq.com(String) <== Updates: 1 Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@237f7970] 2020-07-20 11:16:54.371 INFO 19932 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated... 2020-07-20 11:16:54.707 INFO 19932 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed. 2020-07-20 11:16:54.709 INFO 19932 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor' Process finished with exit code 0
数据库查看：
【主键生成策略】
自增
uuid
redis
zookeeper
snowflake 雪花算法
似乎Mybatis-Plus默认采用的生成策略是雪花算法
如果要更改策略的话使用@TableId注解更改
可以打开看看这个type的枚举类
package com.baomidou.mybatisplus.annotation; public enum IdType { AUTO(0), NONE(1), INPUT(2), ASSIGN_ID(3), ASSIGN_UUID(4), /** @deprecated */ @Deprecated ID_WORKER(3), /** @deprecated */ @Deprecated ID_WORKER_STR(3), /** @deprecated */ @Deprecated UUID(4); private final int key; private IdType(int key) { this.key = key; } public int getKey() { return this.key; } }