java 使用Spring JdbcTemplate -注入数据源vs jdbcTemplate

vohkndzv  于 2023-05-21  发布在  Java
关注(0)|答案(4)|浏览(222)

根据Spring文档,使用Spring JdbcTemplate的步骤如下:

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="
            http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.0.xsd">

        <!-- Scans within the base package of the application for @Components to configure as beans -->
        <context:component-scan base-package="org.springframework.docs.test" />

        <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
            <property name="driverClassName" value="${jdbc.driverClassName}"/>
            <property name="url" value="${jdbc.url}"/>
            <property name="username" value="${jdbc.username}"/>
            <property name="password" value="${jdbc.password}"/>
        </bean>

        <context:property-placeholder location="jdbc.properties"/>

    </beans>

然后

@Repository
    public class JdbcCorporateEventDao implements CorporateEventDao {

        private JdbcTemplate jdbcTemplate;

        @Autowired
        public void setDataSource(DataSource dataSource) {
            this.jdbcTemplate = new JdbcTemplate(dataSource);
        }

        // JDBC-backed implementations of the methods on the CorporateEventDao follow...
    }

基本上,JdbcTemplate是在Component类中使用datasource的setter创建的。
这样做有什么错吗?这样应用程序中就只有一个jdbcTemplate示例。

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"
    p:dataSource-ref="dataSource" 
/>

然后将jdbcTemplate本身直接注入到组件中

@Repository
public class JdbcCorporateEventDao implements CorporateEventDao {
    @Resource("jdbcTemplate")
    private JdbcTemplate jdbcTemplate;

    // JDBC-backed implementations of the methods on the CorporateEventDao follow...
}

有没有什么理由不能将jdbcTemplate本身直接注入到组件类中?
SGB

3htmauhk

3htmauhk1#

你可以做你想做的The javadoc of JdbcTemplate甚至清楚地说:
可以在服务实现中通过直接示例化使用DataSource引用,或者在应用程序上下文中准备并作为bean引用提供给服务。

lvmkulzt

lvmkulzt2#

在spring-context.xml中添加以下内容和

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
    <property name="dataSource" ref="dataSource"/>
</bean>

你可以直接使用jdbcTemplate通过自动装配像

@Autowired JdbcTemplate jdbcTemplate;

例如:

this.jdbcTemplate.query("select * from ******",new RowMapper());
0s7z1bwu

0s7z1bwu3#

你也可以像

@Configuration
@Import({PersistenceConfig.class})
@ComponentScan(basePackageClasses = { 
    ServiceMarker.class,
    RepositoryMarker.class }
)
public class AppConfig {

    /**
     * To resolve ${} in @Values, you must register a static PropertySourcesPlaceholderConfigurer in either XML or 
     * annotation configuration file.
     */
    @Bean
    public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() {
        return new PropertySourcesPlaceholderConfigurer();
    }
}

PersistenceConfig

@Configuration
@PropertySource(value = { "classpath:database/jdbc.properties" })
@EnableTransactionManagement
public class PersistenceConfig {

    @Autowired
    private Environment env;

 /**
  * The @Bean annotation is used to declare a Spring bean and the DI requirements. The @Bean annotation is equivalent to
 *  the <bean> tag, the method name is equivalent to the id attribute within the <bean> tag.
  * 
  * <bean id="mySqlDataSource" class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close" 
        p:driverClassName="${jdbc.mysql.driverClassName}" 
        p:url="${jdbc.mysql.url}"   
        p:username="${jdbc.mysql.username}" 
        p:password="${jdbc.mysql.password}" />
  * 
  * @return
  */
     @Bean(destroyMethod = "close")
     public DataSource mySqlDataSource() {
         BasicDataSource dataSource = new BasicDataSource();
         dataSource.setDriverClassName(env.getProperty("jdbc.mysql.driverClassName"));
         dataSource.setUrl(env.getProperty("jdbc.mysql.url"));
         dataSource.setUsername(env.getProperty("jdbc.mysql.username"));
         dataSource.setPassword(env.getProperty("jdbc.mysql.password"));
         return dataSource;
     }

     @Bean(destroyMethod = "close")
     public DataSource ls360DataSource() {
         BasicDataSource dataSource = new BasicDataSource();
         dataSource.setDriverClassName(env.getProperty("jdbc.ls360.driverClassName"));
         dataSource.setUrl(env.getProperty("jdbc.ls360.url"));
         dataSource.setUsername(env.getProperty("jdbc.ls360.username"));
         dataSource.setPassword(env.getProperty("jdbc.ls360.password"));
         return dataSource;
     } 
}

MySqlDaoImpl

@Repository
public class MySqlDaoImpl implements MySqlDao{

    private static final Logger logger = LogManager.getLogger();

    @Inject
    private DataSource mySqlDataSource;
    private JdbcTemplate mySqlJdbcTemplate;

    @PostConstruct
    public void afterPropertiesSet() throws Exception {
        if (mySqlDataSource == null) {
            throw new BeanCreationException("Must set mySqlDataSource on " + this.getClass().getName());
        }
        this.mySqlJdbcTemplate = new JdbcTemplate(mySqlDataSource);
    }

    @Override
    public void callStoredProcedure(String storedProcedureName, Map<String, Object> inParamMap) throws Exception {

        SimpleJdbcCall simpleJdbcCall = new SimpleJdbcCall(mySqlJdbcTemplate).withProcedureName(storedProcedureName);
        SqlParameterSource in = new MapSqlParameterSource(inParamMap);

        logger.info("Calling stored Procedure: " + storedProcedureName);
        Map<String, Object> simpleJdbcCallResult = simpleJdbcCall.execute(in);
        logger.info("Stored Procedure Result: " + simpleJdbcCallResult);
    }
}

主要

public static void main(String[] args ) {
    try (GenericApplicationContext springContext = new AnnotationConfigApplicationContext(AppConfig.class)) {
        MySQLDao mySqlDao = springContext.getBean(MySQLDaoImpl.class);
        try {
            Map<String, Object> inParamMap = new HashMap<String, Object>();
            inParamMap.put("iCourseId", 1);
            mySqlCourseRenewalDao.callStoredProcedure("usp_processCourseRenewal", inParamMap);
        } catch (Exception e) {
            logger.error("Exception occurs", e);
        }
    } catch (Exception e) {
        logger.error("Exception occurs in loading Spring context: ", e);
    }
}

谢谢

l5tcr1uw

l5tcr1uw4#

注入和共享JdbcTemplate代替底层DataSource在技术上没有什么问题。
但是,共享JdbcTemplate存在一些设计缺陷,这可能有利于注入DataSource

  • JdbcTemplate的使用是DAO的一个实现细节,我们希望隐藏这些细节
  • JdbcTemplate是轻量级的,因此为了提高效率而共享它可能是过早的优化
  • 共享JdbcTemplate并不是没有风险的,因为它有一些可变状态(除了底层DataSource中的可变状态)

这是假设JdbcTemplate与其默认配置(fetchSizemaxRows等)一起使用的典型情况。如果需要配置,则可以在特定方向上驱动设计,例如从上下文注入的共享预配置JdbcTemplate,甚至单个DAO拥有的多个JdbcTemplate示例。

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