Property ‘dataSource’ is required in Spring, Java

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英文:

Property 'dataSource' is required in Spring, Java

问题

我刚开始学习Spring，现在我尝试创建基于Spring JDBC的DAO应用程序。
我按照以下方式创建了配置类：

  1. @Configuration
  2. @ComponentScan("com.foxminded.university")
  3. public class SpringJdbcConfig {
  5.     @Bean
  6.     public DataSource dataSource() {
  7.         DriverManagerDataSource dataSource = new DriverManagerDataSource();
  8.         dataSource.setDriverClassName("org.postgresql.Driver");
  9.         dataSource.setUrl("jdbc:postgresql://127.0.0.1:5432/university");
  10.         dataSource.setUsername("maintainer");
  11.         dataSource.setPassword("12345678");
  12.         return dataSource;
  13.     }
  14. }

DAO类使用了这个Bean：

  1. @Component
  2. public class BuildingDao implements Dao<Building> {
  3.     
  4.     @Autowired
  5.     private DataSource dataSource;
  6.     private final JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
  7.     
  8.     private static final String SAVE_BUILDING = "Insert into buildings (name, floors) values (?,?)";
  10.     @Override
  11.     public void save(Building building) {
  12.         jdbcTemplate.update(SAVE_BUILDING, building.getName(), building.getFloors());
  13.     }
  14. }

但是当我尝试运行这个查询时，我得到了以下错误：

  1. Exception in thread "main" java.lang.IllegalArgumentException: Property 'dataSource' is required

我该如何修复这个问题？据我所见，我使用了@Autowire错误，因为当我使用以下代码时，一切正常运行：

  1. private DataSource dataSource = new SpringJdbcConfig().dataSource();

但这是多余的关系，也是IoC的错误用法。

顺便说一下，在主函数中，我还必须以以下方式使用它：

  1. public class Main {
  2.     public static void main(String[] args) {
  3.         Building building = new SpringJdbcConfig().building();
  4.         building.setName("hghgf");
  5.         building.setFloors(2);
  6.         BuildingDao buildingDao = new SpringJdbcConfig().buildingDao();
  7.         buildingDao.save(building);
  8.     }
  9. }

如果您能解释如何正确使用@Autowired，并将Bean注入主类，我将非常感谢。

英文:

I just started learning Spring, and now I try to crate Spring JDBC based DAO application.
I created config class in this way

  1. @Configuration
  2. @ComponentScan(&quot;com.foxminded.university&quot;)
  3. public class SpringJdbcConfig {
  5.     @Bean
  6.     public DataSource dataSource() {
  7.         DriverManagerDataSource dataSource = new DriverManagerDataSource();
  8.         dataSource.setDriverClassName(&quot;org.postgresql.Driver&quot;);
  9.         dataSource.setUrl(&quot;jdbc:postgresql://127.0.0.1:5432/university&quot;);
  10.         dataSource.setUsername(&quot;maintainer&quot;);
  11.         dataSource.setPassword(&quot;12345678&quot;);
  12.         return dataSource;
  13.     }
  14.  }

And dao-class uses this bean

  1. @Component
  2. public class BuildingDao implements Dao&lt;Building&gt; {
  3.     
  4.     @Autowired
  5.     private DataSource dataSource;
  6.     private final JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
  7.     
  8.     private static final String SAVE_BUILDING = &quot;Insert into buildings (name, floors) values (?,?)&quot;;
  10.     @Override
  11.     public void save(Building building) {
  12.         jdbcTemplate.update(SAVE_BUILDING, building.getName(), building.getFloors());
  13.     }
  14. }

But when I try to run this query i get

  1. Exception in thread &quot;main&quot; java.lang.IllegalArgumentException: Property &#39;dataSource&#39; is required

How I can fix it? As I can see, I use @Autowired incorrectly, because everything works fine when I use

  1.     private DataSource dataSource = new SpringJdbcConfig().dataSource();

But it is extra relation and mistake in terms of IoC.

By the way in main I also have to use this in this way

  1. public class Main {
  2.     public static void main(String[] args) {
  3.         Building building = new SpringJdbcConfig().building();
  4.         building.setName(&quot;hghgf&quot;);
  5.         building.setFloors(2);
  6.         BuildingDao buildingDao = new SpringJdbcConfig().buildingDao();
  7.         buildingDao.save(building);
  8.     }
  9. }

I would be very grateful if you could explain how to use @autowired correctly and inject beans into the main class.

答案1

得分: 1

我建议您按照以下方式使用 Spring Boot 配置您的应用程序。这将初始化并自动配置您大部分的需求。

  1. @SpringBootApplication
  2. @EnableAutoConfiguration
  3. @ComponentScan("com.foxminded.university")
  4. public class SpringBootWebApp {
  5.   public static void main(String[] args) {
  6.     ConfigurableApplicationContext context = SpringApplication.run(SpringBootWebApp.class, args);
  7.     context.registerShutdownHook();
  8.   }
  9. }

之后，您可以使用 @Autowired 来注入所有那些您配置的 Spring 托管的 bean。

英文:

I would suggest you to use spring boot to configure your application as below. This will initialize and auto-configure most of your needs.

  1. @SpringBootApplication
  2. @EnableAutoConfiguration
  3. @ComponentScan(&quot;com.foxminded.university&quot;)
  4. public class SpringBootWebApp {
  5.   public static void main(String[] args) {
  6.     ConfigurableApplicationContext context = SpringApplication.run(SpringBootWebApp.class, args);
  7.     context.registerShutdownHook();
  8.   }
  9. }

After this, you can use @Autowire for all those spring managed beans you configure.

答案2

得分: 0

使用如下方式编写ComponentScan属性，并确保SpringJdbcConfig类位于包com.foxminded.university下：

  1. @ComponentScan(basePackages = "com.foxminded.university")
英文:

Write the ComponentScan attribute as follows and make sure SpringJdbcConfig class is under the package com.foxminded.university*

  1. @ComponentScan(basePackages = &quot;com.foxminded.university&quot;)

huangapple
  • 本文由 发表于 2020年9月22日 00:39:22
  • 转载请务必保留本文链接：https://go.coder-hub.com/63996538.html
  • dependency-injection
  • inversion-of-control
  • java
  • jdbc
  • spring
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