在Java中，我比较ORM熟悉的只有Hibernate和Mybatis,其他的并未实践使用过，在这二者之间我更喜欢Mybatis,因为它精简、灵活(毕竟我是上年纪的程序员，喜欢自己写SQL)。

刚才有提到Mybatis，但是这里的重点是介绍Mybatis-Plus，它是Mybatis的增强版，如果要了解Mybatis的细节的话请点击这里。

简介

据MyBatis-Plus官网介绍，MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，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。这看上去挺香的，所以必须得尝尝。
这里涉及到的环境、组件如下:

• MariaDB 10.3.10
• Windows 10
• IntelliJ IDEA 2019.3.1
• 64 bit JDK 1.8.0_231
• Spring Boot 2.2.3.RELEASE
• Lombok 1.18.10
• Knife4j 2.0.1
• Mybatis-plus 3.3.0
• Druid

Spring Boot 整合Mybatis-Plus

我之前一直是直接用的Mybatis,但是作为喜欢偷懒的人，当然得想办法来提高我们的效率，所以就想着用Mybatis-Plus来省去一些单表的CRUD操作再结合MyBatis-Plus配套的AutoGenerator代码生成器，就能为我们节省不少时间。

引入依赖包

首先，我们得引入Mybatis-Plus和mariadb-java-client等几个包:

<!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger2 -->
       <dependency>
           <groupId>com.github.xiaoymin</groupId>
           <artifactId>knife4j-spring-boot-starter</artifactId>
           <version>2.0.1</version>
       </dependency>
       <!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus-boot-starter -->
       <dependency>
           <groupId>com.baomidou</groupId>
           <artifactId>mybatis-plus-boot-starter</artifactId>
           <version>3.3.0</version>
       </dependency>

       <!-- https://mvnrepository.com/artifact/org.mariadb.jdbc/mariadb-java-client -->
       <dependency>
           <groupId>org.mariadb.jdbc</groupId>
           <artifactId>mariadb-java-client</artifactId>
           <version>2.5.3</version>
       </dependency>

在application.yml配置我们的数据库连接信息

spring:
  datasource:
    driver-class-name: org.mariadb.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/nacos_config?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
    username: root
    password: root
    minimum-idle: 5
    maximum-pool-size: 50
    auto-commit: true
    idle-timeout: 30000
    max-lifetime: 1800000
    connection-timeout: 30000
    connection-test-query: SELECT 1

这里我新建一个名为User的实体,具体属性如下:

@Data
@Builder
@TableName("users")
public class User {
    private String username;
    private String password;
    private int enabled;
}

新建一个UserMapper接口:

public interface UserMapper extends BaseMapper<User> {
}

在我们的启动类加上@MapperScan来指定我们的Mapper扫描目录:

@MapperScan("com.eyiadmin.demo.mapper")
我新建一个单元测试，来试试我们的UserMapper的selectList:

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserTests {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void testUser() {
        List<User> userList = userMapper.selectList(null);
        userList.forEach(System.out::println);
    }
}

会看到Mybatis-Plus为我取出的数据:

2020-01-20 09:44:14.125 TRACE org.apache.ibatis.logging.jdbc.BaseJdbcLogger.trace(BaseJdbcLogger.java:149) 2CNU7X5OLAUE004 --- [           main] c.e.d.m.U.selectList                     : <==    Columns: username, password, enabled
2020-01-20 09:44:14.125 TRACE org.apache.ibatis.logging.jdbc.BaseJdbcLogger.trace(BaseJdbcLogger.java:149) 2CNU7X5OLAUE004 --- [           main] c.e.d.m.U.selectList                     : <==        Row: nacos, $2a$10$EuWPZHzz32dJN7jexM34MOeYirDdFAZm2kuWj7VEOJhhZkDrxfvUu, 1
2020-01-20 09:44:14.131 DEBUG org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:143) 2CNU7X5OLAUE004 --- [           main] c.e.d.m.U.selectList                     : <==      Total: 1
User(username=nacos, password=$2a$10$EuWPZHzz32dJN7jexM34MOeYirDdFAZm2kuWj7VEOJhhZkDrxfvUu, enabled=1)

我们再试试Mybatis-Plus为什么封装的Insert:

@Test
    public void TestUserInsert() {
        int row = userMapper.insert(User.builder().password("aaaa").username("bbbb").enabled(1).build());
        Assert.assertEquals(row, 1);
    }

可以看到日志:

2020-01-20 09:51:32.021 DEBUG org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:143) 2CNU7X5OLAUE004 --- [           main] c.e.d.m.U.insert                         : ==>  Preparing: INSERT INTO users ( username, password, enabled ) VALUES ( ?, ?, ? ) 
2020-01-20 09:51:32.036 DEBUG org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:143) 2CNU7X5OLAUE004 --- [           main] c.e.d.m.U.insert                         : ==> Parameters: bbbb(String), aaaa(String), 1(Integer)

其他高端操作请阅读相关文档https://mp.baomidou.com/guide/quick-start.html

Spring Boot整合Druid数据库连接池

在Spring Boot 2.X默认使用了HikariCP作为数据库连接池,据说hikariCP性能最高(hikariCP>druid>dbcp>c3p0),但是我更喜欢Druid全面的功能和毫不逊色的性能。
开撸吧，首先当然还是引入我们的需要的Druid依赖包:

<!-- https://mvnrepository.com/artifact/com.alibaba/druid-spring-boot-starter -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.1.21</version>
</dependency>

接下来就是修改我们的的application.yml配置:

spring:
  datasource:
    driver-class-name: org.mariadb.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/nacos_config?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
    username: root
    password: root
    ### 连接池配置
    druid:
      initial-size: 50
      max-active: 200
      min-idle: 50
      max-wait: 50
      validation-query: SELECT 1

可以看到我们的日志信息为:

2020-01-20 10:14:54.581  INFO com.alibaba.druid.pool.DruidDataSource.close(DruidDataSource.java:2003) 2CNU7X5OLAUE004 --- [extShutdownHook] c.a.d.p.DruidDataSource                  : {dataSource-1} closing ...
2020-01-20 10:14:54.691  INFO com.alibaba.druid.pool.DruidDataSource.close(DruidDataSource.java:2075) 2CNU7X5OLAUE004 --- [extShutdownHook] c.a.d.p.DruidDataSource                  : {dataSource-1} closed

现在我们增加一个Controller来获取Druid的监控数据:

@RestController
public class DruidStatController {
    @GetMapping("/druid/status")
    public Object druidStat(){
        // DruidStatManagerFacade#getDataSourceStatDataList 该方法可以获取所有数据源的监控数据，除此之外 DruidStatManagerFacade 还提供了一些其他方法，你可以按需选择使用。
        return DruidStatManagerFacade.getInstance().getDataSourceStatDataList();
    }
}

访问http://localhost:8080/druid/status可以得到一个json:

[{
	"Identity": 1914285129,
	"Name": "DataSource-1914285129",
	"DbType": "mysql",
	"DriverClassName": "org.mariadb.jdbc.Driver",
	"URL": "jdbc:mysql://127.0.0.1:3306/nacos_config?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true",
	"UserName": "root",
	"FilterClassNames": [],
	"WaitThreadCount": 0,
	"NotEmptyWaitCount": 0,
	"NotEmptyWaitMillis": 0,
	"PoolingCount": 50,
	"PoolingPeak": 50,
	"PoolingPeakTime": "2020-01-20T02:26:22.466+0000",
	"ActiveCount": 0,
	"ActivePeak": 0,
	"ActivePeakTime": null,
	"InitialSize": 50,
	"MinIdle": 50,
	"MaxActive": 200,
	"QueryTimeout": 0,
	"TransactionQueryTimeout": 0,
	"LoginTimeout": 0,
	"ValidConnectionCheckerClassName": null,
	"ExceptionSorterClassName": null,
	"TestOnBorrow": false,
	"TestOnReturn": false,
	"TestWhileIdle": true,
	"DefaultAutoCommit": true,
	"DefaultReadOnly": null,
	"DefaultTransactionIsolation": null,
	"LogicConnectCount": 0,
	"LogicCloseCount": 0,
	"LogicConnectErrorCount": 0,
	"PhysicalConnectCount": 50,
	"PhysicalCloseCount": 0,
	"PhysicalConnectErrorCount": 0,
	"DiscardCount": 0,
	"ExecuteCount": 0,
	"ExecuteUpdateCount": 0,
	"ExecuteQueryCount": 0,
	"ExecuteBatchCount": 0,
	"ErrorCount": 0,
	"CommitCount": 0,
	"RollbackCount": 0,
	"PSCacheAccessCount": 0,
	"PSCacheHitCount": 0,
	"PSCacheMissCount": 0,
	"StartTransactionCount": 0,
	"TransactionHistogram": [0, 0, 0, 0, 0, 0, 0],
	"ConnectionHoldTimeHistogram": [0, 0, 0, 0, 0, 0, 0, 0],
	"RemoveAbandoned": false,
	"ClobOpenCount": 0,
	"BlobOpenCount": 0,
	"KeepAliveCheckCount": 0,
	"KeepAlive": false,
	"FailFast": false,
	"MaxWait": 50,
	"MaxWaitThreadCount": -1,
	"PoolPreparedStatements": false,
	"MaxPoolPreparedStatementPerConnectionSize": 10,
	"MinEvictableIdleTimeMillis": 1800000,
	"MaxEvictableIdleTimeMillis": 25200000,
	"LogDifferentThread": true,
	"RecycleErrorCount": 0,
	"PreparedStatementOpenCount": 0,
	"PreparedStatementClosedCount": 0,
	"UseUnfairLock": true,
	"InitGlobalVariants": false,
	"InitVariants": false
}]

我们还可以打开stat-view-servlet,需要加入如下配置:

spring:
 datasource:
 druid:
 stat-view-servlet:
 enabled: true
 login-username: admin
 login-password: admin

这是启动后，访问http://localhost:8080/druid/index.html页面就会跳转到登录页面,输入我们配置的用户名和密码admin/admin:

可以看到Druid提供的功能是比较全面的，另外在第三张图可以看到我们的相关参数，大家也可以参照这个来配置连接池。

MyBatis-Plus的代码生成器

Mybatis有Generator工具为我们提高编码效率，MyBatis-Plus也不示弱，它也提供有MyBatis-Plus AutoGenerator 。在上面的简单实体只有3个属性，假如有几十个属性怎么办呢？这时候AutoGenerator就可以帮我们一个大忙。首先引入所需包:

<!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus-generator -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>3.3.0</version>
        </dependency>
<!-- https://mvnrepository.com/artifact/org.apache.velocity/velocity-engine-core -->
<dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity-engine-core</artifactId>
    <version>2.1</version>
</dependency>

具体使用方式，可以去`mybatis-plus`官网查看详细教程

Knife4j的使用

这里我引入了Knife4j包:

<!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger2 -->
        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>2.

新建一个SwaggerConfiguration类配置我们的Swagger:

@Configuration
@EnableSwagger2
@EnableKnife4j
@Import(BeanValidatorPluginsConfiguration.class)
public class SwaggerConfiguration {
    @Bean("createRestApi")
    public Docket createRestApi() {
        return new Docket(DocumentationType.SWAGGER_2)
                .apiInfo( new ApiInfoBuilder()
                        //页面标题
                        .title("Demo Web Api文档")
                        //创建人
                        .contact(new Contact("eyiadmin", "https://springfox.github.io/springfox/", "eyiadmin@163.com"))
                        .version("1.0")
                        .description("Demo Web Api文档")
                        .build())
                .select()
                //API接口所在的包位置
                .apis(RequestHandlerSelectors.basePackage("com.eyiadmin.demo.controller"))
                .paths(PathSelectors.any())
                .build();

    }

}

新建一个名为UserController的Controller:

@RequestMapping("/v1/user")
@RestController
@Api(tags = "User API展示")
public class UserController {

    @Autowired
    UserMapper userMapper;

    @GetMapping("/list")
    public ResponseResult<?> getUserList()
    {
        return ResponseResult.success(userMapper.selectList(null));
    }
}

启动起来，访问localhost:8080/doc.html:

调用我们的接口，可以看到Druid监控到了我们SQL语句的执行情况

过于Swagger也可以看看我之前的一篇文章Spring Boot集成Swagger