Spring Boot属性注入的几种方式总结[代码实例]

Java配置

• JdbcConfig.java

/*
@Configuration：声明一个类作为配置类，代替xml文件
@Bean：声明在方法上，将方法的返回值加入Bean容器，代替<bean>标签
@value：属性注入
@PropertySource：指定外部属性文件，
**/
@Configuration
@PropertySource("classpath:jdbc.properties")
public class JdbcConfig {
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.driver}")
    private String driver;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;

    @Bean
    public DataSource dataSource(){
        DruidDataSource druidDataSource = new DruidDataSource();
        druidDataSource.setUrl(url);
        druidDataSource.setUsername(username);
        druidDataSource.setPassword(password);
        druidDataSource.setDriverClassName(driver);
        return druidDataSource;
    }
}

• jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/springboot?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456

• MyController.java

@RestController
public class MyController {

    @Autowired
    private DataSource dataSource;

    @RequestMapping("hello")
    public String hello(){
        System.out.println(dataSource);
        return "hello spring boot";
    }
}

• Application.java

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }
}

• Debug代码
  

---

• Spring Boot 对上面的属性注入方式进行了改进，使得代码更加简洁和易于理解。

单独放到一个类中

• JdbcConfig.java

@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfig {

    @Autowired
    private JdbcProperties jdbcProperties;
   //或者 接当做参数传入 public DataSource dataSource(JdbcProperties jdbcProperties){}
   //或者 以构造方法的形式传入

    @Bean
    public DataSource dataSource(){
        DruidDataSource druidDataSource = new DruidDataSource();
        druidDataSource.setUrl(jdbcProperties.getUrl());
        druidDataSource.setPassword(jdbcProperties.getPassword());
        druidDataSource.setDriverClassName(jdbcProperties.getDriver());
        druidDataSource.setUsername(jdbcProperties.getUsername());
        return druidDataSource;
    }
}

• JdbcProperties.java

@ConfigurationProperties(prefix = "jdbc")
@Data  //lombok 的注解，用于实现get和set方法
public class JdbcProperties {
    private String url;
    private String driver;
    private String username;
    private String password;
}

• application.properties
  (注意这个配置文件的名字不能改，系统默认，不能改变)

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/springboot?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456

• MyController.java

@RestController
public class MyController {

    @Autowired
    private DataSource dataSource;

    @RequestMapping("hello")
    public String hello(){
        System.out.println(dataSource);
        return "hello spring boot";
    }
}

• Application.java

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }
}

• Debug代码
  

直接注入

• 这种方法只适用于这个属性只需要给当前的对象使用，不适用于公共属性。
• JdbcConfig.java

@Configuration
public class JdbcConfig {
    @Bean
    @ConfigurationProperties(prefix = "jdbc")
    public DataSource dataSource(){
        DruidDataSource druidDataSource = new DruidDataSource();
        return druidDataSource;
    }
}

• application.properties
  (注意这个配置文件的名字不能改，系统默认，不能改变)
• 配置文件的中必须用 driverClassName ，否则会报错。

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/springboot?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456

• MyController.java

@RestController
public class MyController {

    @Autowired
    private DataSource dataSource;

    @RequestMapping("hello")
    public String hello(){
        System.out.println(dataSource);
        return "hello spring boot";
    }
}

• Application.java

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }
}

• Debug代码
  

属性文件使用yaml文件方式

• JdbcProperties.java

@Component
@ConfigurationProperties(prefix = "jdbc")
@Data  //lombok 的注解，用于实现get和set方法
public class JdbcProperties {

    private String url;
    private String driver;
    private String username;
    private String password;
}

• application.yaml
  (YAML 配置文件语言)

jdbc:
  driver: com.mysql.jdbc.Driver
  url: jdbc:mysql://localhost:3306/springboot?characterEncoding=utf-8
  username: root
  password: 123456

• MyController.java

@RestController
public class MyController {
    @Autowired
    private JdbcProperties jdbcProperties;

    @RequestMapping("hello")
    public String hello(){
        System.out.println(jdbcProperties);
        return "hello spring boot";
    }
}

• Application.java

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }
}

• Debug代码
  
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