Spring JPA:属性文件中的外部数据库配置不起作用

Question

我想使用外部属性文件来加载数据库和 REST 端点信息。我试图避免XML配置，而倾向于基于注释的配置。

我创建了 2 个类，这两个类都用@Configuration注释，并在其构造函数中使用@Value注释来加载属性：

其余配置.java

@Configuration
public class RestConfiguration {
private final String grantType;
private final AuthenticationScheme authenticationScheme;
private final String clientId;
private final String clientSecret;
private final String accessTokenUri;
private final boolean useProxy;
private final String proxyHost;
private final int proxyPort;
@Autowired
public RestConfiguration(
@Value("${api.oauth2.grant-type}") String grantType,
@Value("${api.oauth2.authentication-scheme}") AuthenticationScheme authenticationScheme,
@Value("${api.oauth2.client-id}") String clientId,
@Value("${api.oauth2.client-secret}") String clientSecret,
@Value("${api.oauth2.url}") String accessTokenUri,
@Value("${net.proxy}") boolean useProxy,
@Value("${net.proxy.host}") String proxyHost,
@Value("${net.proxy.port}") int proxyPort) {
this.grantType = grantType;
this.authenticationScheme = authenticationScheme;
this.clientId = clientId;
this.clientSecret = clientSecret;
this.accessTokenUri = accessTokenUri;
this.useProxy = useProxy;
this.proxyHost = proxyHost;
this.proxyPort = proxyPort;
} 
}

持久性配置.java

@Configuration
public class PersistenceConfiguration {
private final String host;
private final String port;
private final String database;
private final String schema;
private final String user;
private final String password;
@Autowired
public PersistenceConfiguration(
@Value("${db.host}") String host,
@Value("${db.port}") String port,
@Value("${db.database}") String database,
@Value("${db.schema}") String schema,
@Value("${db.user}") String user,
@Value("${db.password}") String password) {
this.host = host;
this.port = port;
this.database = database;
this.schema = schema;
this.user = user;
this.password = password;
}
@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
em.setDataSource(dataSource);
em.setPackagesToScan("ch.example.rest.entities");
JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
em.setJpaVendorAdapter(vendorAdapter);
em.setJpaProperties(additionalProperties());
return em;
}
@Bean
public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName("org.postgresql.Driver");
dataSource.setUrl("jdbc:postgresql://" + host + ":" + port + "/" + database);
dataSource.setUsername(user);
dataSource.setPassword(password);
dataSource.setSchema(schema);
return dataSource;
}
@Bean
public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
JpaTransactionManager transactionManager = new JpaTransactionManager();
transactionManager.setEntityManagerFactory(emf);
return transactionManager;
}
@Bean
public PersistenceExceptionTranslationPostProcessor exceptionTranslation() {
return new PersistenceExceptionTranslationPostProcessor();
}
Properties additionalProperties() {
Properties properties = new Properties();
properties.setProperty("hibernate.hbm2ddl.auto", "none");
properties.setProperty("hibernate.dialect", "org.hibernate.dialect.PostgreSQL95Dialect");
properties.setProperty(
"hibernate.physical_naming_strategy",
"ch.example.rest.configurations.SnakeCaseNamingStrategy");
properties.setProperty(
"spring.datasource.hikari.data-source-properties", "stringtype=unspecified");
return properties;
}
}

两个配置文件驻留在同一个包(子包configurations(中。

初始化 Spring 上下文的类如下所示：

@Configuration
@ComponentScan(basePackages = "ch.example.rest")
@EnableJpaRepositories("ch.example.rest.repositories")
@PropertySource("classpath:application.properties")
public class RestClient {
private CommandLineController commandLineController;
@Autowired
public RestClient(CommandLineController commandLineController) {
this.commandLineController = commandLineController;
}
private static void main(String[] args) {
// ... some parsing of command line arguments
// Initialize context
ApplicationContext ctx = new AnnotationConfigApplicationContext(RestClient.class);
RestClient restClient = ctx.getBean(RestClient.class, uploadCommand);
restClient.runCommand(parsedCommand, uploadCommand);
}
public void runCommand(String command, UploadBillsCommand uploadCommand) {
// Some calls to a controller
commandLineController....;
}
}

有趣的是，RestConfiguration类接收属性，但PersistenceConfiguration不会。在调试过程中，我注意到PersistenceConfiguration类几乎是立即构造的，而RestConfiguration是在一段时间后加载的，当第一次调用 RestTemplate 时。

我怀疑这可能与Spring JPA尝试连接存储库这一事实有关，因此需要在启动时建立SQL连接。

我发现这个问题似乎表明，如果没有额外的样板代码，就不可能在外部提供数据库配置。由于这个问题已经有 5 年的历史了，我想知道是否有另一种优雅的解决方案来解决这个问题，而无需创建第二个上下文。

Answer 1

好吧，所以答案似乎很简单。与其让 Spring 使用带有@Value注释的表达式语言加载属性，我只需要注入一个Environment实例，然后直接从中获取属性：

@Configuration
public class PersistenceConfiguration {
private String host;
private String port;
private String database;
private String schema;
private String user;
private String password;
@Autowired
public PersistenceConfiguration(Environment environment) {
this.host = environment.getProperty("db.host");
this.port = environment.getProperty("db.port");
this.database = environment.getProperty("db.database");
this.schema = environment.getProperty("db.schema");
this.user = environment.getProperty("db.user");
this.password = environment.getProperty("db.password");
}
}