springboot2.0整合druid，以及springboot自动装配DataSource原理

墨蓝 2021-09-28 04:08 712阅读 0赞

1.springboot 目前的推荐版是2.1.2.RELEASE，我们就以当前最新的推荐版为例

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2.创建项目，引入对应的jar包，我是以maven的形式

父级的pom

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.2.RELEASE</version>
            <relativePath /> 
        </parent>

引入的包

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-jdbc</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid-spring-boot-starter</artifactId>
                <version>1.1.10</version>
            </dependency>

3.配置文件，更新详细的配置 请参考 阿里的github查看，[网址][Link 1]；里面介绍了更详细的属性含义，以及多数据源的配置方式

spring:
      datasource:
        url: jdbc:mysql://localhost:3306/test
        username: root
        password: 123456
        driver-class-name: com.mysql.jdbc.Driver
        type: com.alibaba.druid.pool.DruidDataSource
        druid:
          initial-size: 8
          min-idle: 1
          max-active: 20
          max-wait: 60000
          time-between-eviction-runsMillis: 60000
          min-evictable-idle-timeMillis: 300000
          validation-query: select 'x' FROM DUAL
          test-while-idle: true
          test-on-borrow: false
          test-on-return: false
          pool-prepared-statements: true
          max-open-prepared-statements: 20
          max-pool-prepared-statement-per-connection-size: 20
          filters: stat
          connection-properties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
          use-global-data-source-stat: true

4.测试类，debug运行，可以看到，DataSource接口的实现类就是durid的实现类，可以继续找到配置文件中的一些初始化参数

initial-size: 8  
      min-idle: 1  
      max-active: 20  
      max-wait: 60000

@RunWith(SpringRunner.class)
    @SpringBootTest(classes = { BadgerDruidApplication.class })
    public class BadgerDruidApplicationTests {
    
        @Autowired
        DataSource dataSource;
    
        @Test
        public void contextLoads() throws SQLException {
            Connection connection = dataSource.getConnection();
            PreparedStatement prepareStatement = connection
                    .prepareStatement("select * from t_city where parent_id='-1'");
            ResultSet resultSet = prepareStatement.executeQuery();
            while (resultSet.next()) {
                String cityName = resultSet.getString("name");
                System.out.println(cityName);
            }
        }
    }

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至此，druid就与springboot2.0集成完成了；当然中间也会有springboot2.0 mysql的驱动包，跟服务端版本不匹配的异常

java.sql.SQLNonTransientConnectionException: CLIENT\_PLUGIN\_AUTH is required

替换下mysql驱动的版本

5.下面讲一点springboot对DataSource的一些自动装配原理，以及另一种druid的方式

spring-boot-autoconfigure-2.1.2.RELEASE.jar包下的org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration类

@Configuration
    @ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
    @EnableConfigurationProperties(DataSourceProperties.class)
    @Import({ DataSourcePoolMetadataProvidersConfiguration.class,
    		DataSourceInitializationConfiguration.class })
    public class DataSourceAutoConfiguration {
    
    	@Configuration
    	@Conditional(EmbeddedDatabaseCondition.class)
    	@ConditionalOnMissingBean({ DataSource.class, XADataSource.class })
    	@Import(EmbeddedDataSourceConfiguration.class)
    	protected static class EmbeddedDatabaseConfiguration {
    
    	}
    
    	@Configuration
    	@Conditional(PooledDataSourceCondition.class)
    	@ConditionalOnMissingBean({ DataSource.class, XADataSource.class })
    	@Import({ DataSourceConfiguration.Hikari.class, DataSourceConfiguration.Tomcat.class,
    			DataSourceConfiguration.Dbcp2.class, DataSourceConfiguration.Generic.class,
    			DataSourceJmxConfiguration.class })
    	protected static class PooledDataSourceConfiguration {
    
    	}
    
    	/**
    	 * {@link AnyNestedCondition} that checks that either {@code spring.datasource.type}
    	 * is set or {@link PooledDataSourceAvailableCondition} applies.
    	 */
    	static class PooledDataSourceCondition extends AnyNestedCondition {
    
    		PooledDataSourceCondition() {
    			super(ConfigurationPhase.PARSE_CONFIGURATION);
    		}
    
    		@ConditionalOnProperty(prefix = "spring.datasource", name = "type")
    		static class ExplicitType {
    
    		}
    
    		@Conditional(PooledDataSourceAvailableCondition.class)
    		static class PooledDataSourceAvailable {
    
    		}
    
    	}

我们先看类上@Import(\{ DataSourcePoolMetadataProvidersConfiguration.class,DataSourceInitializationConfiguration.class \})

DataSourcePoolMetadataProvidersConfiguration导入这个类的实例，点进去可以看到

@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)

@ConditionalOnClass(HikariDataSource.class)

@ConditionalOnClass(BasicDataSource.class)

这3个数据源的装配，都是导入了这些数据源，才会实例创建成功；而springboot2.0的默认生效的HikariDataSource数据源；如图所示，spring-boot-starter-jdbc默认依赖了；而在springboot1.x中，默认生效的org.apache.tomcat.jdbc.pool.DataSource.class

![20190131110242845.png][]

现在我们看下根据spring.datasource.type指定类型的实例化，只拿了一部分主要的，我们主要来看PooledDataSourceConfiguration 这个内部类

@Configuration
    	@Conditional(PooledDataSourceCondition.class)
    	@ConditionalOnMissingBean({ DataSource.class, XADataSource.class })
    	@Import({ DataSourceConfiguration.Hikari.class, DataSourceConfiguration.Tomcat.class,
    			DataSourceConfiguration.Dbcp2.class, DataSourceConfiguration.Generic.class,
    			DataSourceJmxConfiguration.class })
    	protected static class PooledDataSourceConfiguration {
    
    	}

@Conditional(PooledDataSourceCondition.class) 根据判断条件，实例化这个类，指定了配置文件中，必须有type这个属性

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实例化后，@Import 会导入DataSourceConfiguration 这个类；在DataSourceConfiguration这个类中，就是具体的DataSource接口实现；我们默认导入web模块后，会导入tomcat，并且实例化org.apache.tomcat.jdbc.pool.DataSource

/**
    	 * Tomcat Pool DataSource configuration.
    	 */
    	 //只要导入了这个org.apache.tomcat.jdbc.pool.DataSource.class，就会生效
    	@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
    	//没有DataSource的实例
    	@ConditionalOnMissingBean(DataSource.class)
    	//配置了spring.datasource.type 并且值为org.apache.tomcat.jdbc.pool.DataSource，才会生效；
    	//matchIfMissing=true表示，就算没有配置spring.datasource.type，也会生效
    	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource", matchIfMissing = true)
    	static class Tomcat {
    
    		@Bean
    		@ConfigurationProperties(prefix = "spring.datasource.tomcat")
    		public org.apache.tomcat.jdbc.pool.DataSource dataSource(
    				DataSourceProperties properties) {
    			org.apache.tomcat.jdbc.pool.DataSource dataSource = createDataSource(
    					properties, org.apache.tomcat.jdbc.pool.DataSource.class);
    			DatabaseDriver databaseDriver = DatabaseDriver
    					.fromJdbcUrl(properties.determineUrl());
    			String validationQuery = databaseDriver.getValidationQuery();
    			if (validationQuery != null) {
    				dataSource.setTestOnBorrow(true);
    				dataSource.setValidationQuery(validationQuery);
    			}
    			return dataSource;
    		}
    
    	}

另外springboot 默认支持 type 类型设置的数据源；

@Import(\{ DataSourceConfiguration.Hikari.class, DataSourceConfiguration.Tomcat.class,  
            DataSourceConfiguration.Dbcp2.class, DataSourceConfiguration.Generic.class,  
            DataSourceJmxConfiguration.class \})

具体的，接着DataSourceConfiguration类看就可以了，

下面说下，集成druid 在DataSourceConfiguration类，最后的部分

/**
    	 * Generic DataSource configuration.
    	 */
    	@ConditionalOnMissingBean(DataSource.class)
    	@ConditionalOnProperty(name = "spring.datasource.type")
    	static class Generic {
    
    		@Bean
    		public DataSource dataSource(DataSourceProperties properties) {
    			return properties.initializeDataSourceBuilder().build();
    		}
    
    	}

如果上面，都不生效，就会执行这个；我们直接看 return properties.initializeDataSourceBuilder().build(); 这个build方法；

@SuppressWarnings("unchecked")
    	public T build() {
    		Class<? extends DataSource> type = getType();
    		DataSource result = BeanUtils.instantiateClass(type);
    		maybeGetDriverClassName();
    		bind(result);
    		return (T) result;
    	}

拿到上述配置文件中的com.alibaba.druid.pool.DruidDataSource 这个类的全类名，反射实例化；至此，datasource的实例过程，就说完了；最后我们看下，阿里官方封装的druid-spring-boot-starter，直接简单粗暴的创建了一个datasource的实现，有感性的朋友，也可以看下DruidDataSourceWrapper 的具体实现，就不在继续描述

@Configuration
    @ConditionalOnClass(DruidDataSource.class)
    @AutoConfigureBefore(DataSourceAutoConfiguration.class)
    @EnableConfigurationProperties({DruidStatProperties.class, DataSourceProperties.class})
    @Import({DruidSpringAopConfiguration.class,
        DruidStatViewServletConfiguration.class,
        DruidWebStatFilterConfiguration.class,
        DruidFilterConfiguration.class})
    public class DruidDataSourceAutoConfigure {
    
        private static final Logger LOGGER = LoggerFactory.getLogger(DruidDataSourceAutoConfigure.class);
    
        @Bean(initMethod = "init")
        @ConditionalOnMissingBean
        public DataSource dataSource() {
            LOGGER.info("Init DruidDataSource");
            return new DruidDataSourceWrapper();
        }
    }

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[Link 1]: https://github.com/alibaba/druid/tree/master/druid-spring-boot-starter
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[20190131110242845.png]: /images/20210923/56451c0e077741dcb50829ea31dfa3b8.png
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