spring boot 注入屬性的幾種方式

1.@PropertySource：指定屬性文件的路徑  如 classpath:jdbc.properties

@Configuration
@PropertySource("classpath:jdbc.properties")
public class JdbcConfiguration {

    @Value("${jdbc.url}")
    String url;
    @Value("${jdbc.driverClassName}")
    String driverClassName;
    @Value("${jdbc.username}")
    String username;
    @Value("${jdbc.password}")
    String password;

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

2. 通過@ConfigurationProperties注解聲明當前類為屬性讀取類  

      prefix="jdbc"讀取屬性文件中，前綴為jdbc的值。

沒有指定屬性文件的地址，SpringBoot默認會讀取文件名為application.properties的資源文件

@ConfigurationProperties(prefix = "jdbc")
public class JdbcProperties {
    private String url;
    private String driverClassName;
    private String username;
    private String password;
  
}

   通過@EnableConfigurationProperties(JdbcProperties.class)來聲明要使用JdbcProperties這個類的對象

   Autowired 注入 

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

    @Autowired
    private JdbcProperties jdbcProperties;

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

}

  構造函數注入 

 

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

    private JdbcProperties jdbcProperties;

    public JdbcConfiguration(JdbcProperties jdbcProperties){
        this.jdbcProperties = jdbcProperties;
    }

    @Bean
    public DataSource dataSource() {
        // 略
    }

}

 

@Bean方法的參數注入

 

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

    @Bean
    public DataSource dataSource(JdbcProperties jdbcProperties) {
        // ...
    }
}

 

 

3    我們直接把@ConfigurationProperties(prefix = "jdbc")聲明在需要使用的@Bean的方法上，然后SpringBoot就會自動調用這個Bean（此處是DataSource）的set方法，然后完成注入。使用的前提是：該類必須有對應屬性的set方法！

@Configuration
public class JdbcConfiguration {
    
    @Bean
    // 聲明要注入的屬性前綴，SpringBoot會自動把相關屬性通過set方法注入到DataSource中
    @ConfigurationProperties(prefix = "jdbc")
    public DataSource dataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        return dataSource;
    }
}