# spring-boot-jdbctemplate

**Repository Path**: caychen/spring-boot-jdbctemplate

## Basic Information

- **Project Name**: spring-boot-jdbctemplate
- **Description**: No description available
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 0
- **Created**: 2018-04-02
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

## 1、添加数据源依赖：

既然要使用JdbcTemplate，则需要添加jdbc的依赖。

```xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
```



## 2、连接数据源，以mysql为例：

```xml
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>
```



## 3、在src/main/resources/application.properties中配置数据源信息

注意：其中driver-class可以不写，Spring Boot会自动从url中解析使用的数据源类

Spring Boot默认采用**tomcat-jdbc**连接池，如果需要**C3P0，DBCP，Druid**等作为连接池，需要加入相关依赖以及配置，这里不作说明，采用默认配置即可。

```properties
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=...
spring.datasource.password=...
```

**底层默认使用tomcat-jdbc连接池，所以在默认情况下会创建一个基于Tomcat连接池的DataSource，并注入到Spring IOC容器中。**

```java
abstract class DataSourceConfiguration {

	@SuppressWarnings("unchecked")
	protected <T> T createDataSource(DataSourceProperties properties,
			Class<? extends DataSource> type) {
		return (T) properties.initializeDataSourceBuilder().type(type).build();
	}

	/**
	 * Tomcat Pool DataSource configuration.
	 */
	@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource", matchIfMissing = true)
	static class Tomcat extends DataSourceConfiguration {

        //创建一个基于Tomcat连接池的DataSource的Bean
        //由于底层使用Tomcat连接池，在不引入外部数据连接池的jar包之前，默认使用Tomcat的DataSource
		@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;
		}

	}

	/**
	 * Hikari DataSource configuration.
	 */
	@ConditionalOnClass(HikariDataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "com.zaxxer.hikari.HikariDataSource", matchIfMissing = true)
	static class Hikari extends DataSourceConfiguration {

        //创建基于hikari的DataSource的Bean
		@Bean
		@ConfigurationProperties(prefix = "spring.datasource.hikari")
		public HikariDataSource dataSource(DataSourceProperties properties) {
			return createDataSource(properties, HikariDataSource.class);
		}

	}

	/**
	 * DBCP DataSource configuration.
	 *
	 * @deprecated as of 1.5 in favor of DBCP2
	 */
	@ConditionalOnClass(org.apache.commons.dbcp.BasicDataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp.BasicDataSource", matchIfMissing = true)
	@Deprecated
	static class Dbcp extends DataSourceConfiguration {

        //创建基于dbcp的DataSource的Bean
		@Bean
		@ConfigurationProperties(prefix = "spring.datasource.dbcp")
		public org.apache.commons.dbcp.BasicDataSource dataSource(
				DataSourceProperties properties) {
			org.apache.commons.dbcp.BasicDataSource dataSource = createDataSource(
					properties, org.apache.commons.dbcp.BasicDataSource.class);
			DatabaseDriver databaseDriver = DatabaseDriver
					.fromJdbcUrl(properties.determineUrl());
			String validationQuery = databaseDriver.getValidationQuery();
			if (validationQuery != null) {
				dataSource.setTestOnBorrow(true);
				dataSource.setValidationQuery(validationQuery);
			}
			return dataSource;
		}

	}

	/**
	 * DBCP DataSource configuration.
	 */
	@ConditionalOnClass(org.apache.commons.dbcp2.BasicDataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp2.BasicDataSource", matchIfMissing = true)
	static class Dbcp2 extends DataSourceConfiguration {

        //创建基于dbcp2的DataSource的Bean
		@Bean
		@ConfigurationProperties(prefix = "spring.datasource.dbcp2")
		public org.apache.commons.dbcp2.BasicDataSource dataSource(
				DataSourceProperties properties) {
			return createDataSource(properties,
					org.apache.commons.dbcp2.BasicDataSource.class);
		}
	}
    
   	/**
	 * Generic DataSource configuration.
	 */
	@ConditionalOnMissingBean(DataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type")
	static class Generic {

        //可以在配置文件中通过spring.datasource.type指定外部的dataSource类型，并创建基于该type的DataSource的Bean
		@Bean
		public DataSource dataSource(DataSourceProperties properties) {
			return properties.initializeDataSourceBuilder().build();
		}

	}
}
```





## 4、使用JdbcTemplate操作数据库

> SpringBoot中的 **JdbcTemplate** 是自动配置的，可以直接使用 **@Autowired** 或者 **@Resource** 来注入到需要的类中。

#### **==JdbcTemplateAutoConfiguration==**

```java
@Configuration
@ConditionalOnClass({ DataSource.class, JdbcTemplate.class })
@ConditionalOnSingleCandidate(DataSource.class)
//在DataSourceAutoConfiguration自动配置类完成后再进行自动配置该类JdbcTemplateAutoConfiguration
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class JdbcTemplateAutoConfiguration {

	private final DataSource dataSource;

	public JdbcTemplateAutoConfiguration(DataSource dataSource) {
		this.dataSource = dataSource;
	}

    //创建一个JdbcTemplate的Bean
	@Bean
	@Primary
	@ConditionalOnMissingBean(JdbcOperations.class)
	public JdbcTemplate jdbcTemplate() {
		return new JdbcTemplate(this.dataSource);
	}

	@Bean
	@Primary
	@ConditionalOnMissingBean(NamedParameterJdbcOperations.class)
	public NamedParameterJdbcTemplate namedParameterJdbcTemplate() {
		return new NamedParameterJdbcTemplate(this.dataSource);
	}

}

```

​	在**JdbcTemplateAutoConfiguration**类中会创建一个**JdbcTemplate**的Bean，所以在使用的时候可以直接注入。



#### **==DataSourceAutoConfiguration==**

```java
@Configuration
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
//启动DataSourceProperties配置类
@EnableConfigurationProperties(DataSourceProperties.class)
@Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class })
public class DataSourceAutoConfiguration {

	private static final Log logger = LogFactory
			.getLog(DataSourceAutoConfiguration.class);

	@Bean
	@ConditionalOnMissingBean
	public DataSourceInitializer dataSourceInitializer(DataSourceProperties properties,
			ApplicationContext applicationContext) {
        //根据配置文件属性创建DataSource的初始化器
		return new DataSourceInitializer(properties, applicationContext);
	}
    
    //...
}
```



#### **==DataSourceInitializer==**

```java
class DataSourceInitializer implements ApplicationListener<DataSourceInitializedEvent> {
    private final DataSourceProperties properties;

	private final ApplicationContext applicationContext;

	private DataSource dataSource;

	private boolean initialized = false;

	DataSourceInitializer(DataSourceProperties properties,
			ApplicationContext applicationContext) {
		this.properties = properties;
		this.applicationContext = applicationContext;
	}

	@PostConstruct
	public void init() {
        //当DataSourceProperties初始化完成后
		if (!this.properties.isInitialize()) {
			logger.debug("Initialization disabled (not running DDL scripts)");
			return;
		}
		if (this.applicationContext.getBeanNamesForType(DataSource.class, false,
				false).length > 0) {
            //获取DataSource的bean
			this.dataSource = this.applicationContext.getBean(DataSource.class);
		}
		if (this.dataSource == null) {
			logger.debug("No DataSource found so not initializing");
			return;
		}
		//...
	}
}
```

![](images/DataSource注入.png)

​	最后使用**JdbcTemplate**操作数据库，就类似在Spring框架中使用**JdbcTemplate**一样，这里就不再累赘了。

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