Spring properties configuration using @PropertySource

Question

In the below Spring configuration class, I'm loading app.properties file via @PropertySource and constructing 2 different DBCP data sources using the configurations from the properties file.

Though everything works fine, I don't like declaring a variable for each configuration property with an annotation in order to construct the data source. I tried to autowire Environment class like this

@Autowired Environment env;

However, when env.getProperty() returns null. Is there a better way to do this?

@Configuration
@PropertySource("classpath:app.properties")
public class DAOConfig {
    @Value( "${txn.dbhost}" ) private String txnDbHost;
    @Value( "${txn.dbport}" ) private Integer txnDbPort;
    @Value( "${txn.dbservice}" ) private String txnDbService;
    @Value( "${txn.dbuser}" ) private String txnDbUser;
    @Value( "${txn.dbpwd}" ) private String txnDbPwd;

    @Value( "${rpt.dbhost}" ) private String rptDbHost;
    @Value( "${rpt.dbport}" ) private Integer rptDbPort;
    @Value( "${rpt.dbservice}" ) private String rptDbService;
    @Value( "${rpt.dbuser}" ) private String rptDbUser;
    @Value( "${rpt.dbpwd}" ) private String rptDbPwd;

    @Bean(destroyMethod = "close")
    public DataSource txnDataSource() {
        return new DataSources.Builder()
                .host(txnDbHost)
                .port(txnDbPort)
                .service(txnDbService)
                .user(txnDbUser)
                .pwd(txnDbPwd)
                .build();
    }

    @Bean(destroyMethod = "close")
    public DataSource rptDataSource() {
        return new DataSources.Builder()
                .host(rptDbHost)
                .port(rptDbPort)
                .service(rptDbService)
                .user(rptDbUser)
                .pwd(rptDbPwd)
                .build();
    }
}

Edit : I take that back about Environment.getProperty() not working. It indeed works. I was giving property names incorrectly. For those who don't want to use Spring Boot, you could autowire Environment as use it as follows:

@Configuration
@PropertySource("classpath:app.properties")
public class DAOConfig {
    @Autowired Environment env;

    @Bean(destroyMethod = "close")
    public DataSource txnDataSource() {
        return new DataSources.Builder()
                .host(env.getProperty("txn.dbhost"))
                .port(env.getProperty("txn.dbport"))
                .service(env.getProperty("txn.dbservice"))
                .user(env.getProperty("txn.dbuser"))
                .pwd(env.getProperty("txn.dbpwd"))
                .build();
    }

}

Answer 1

If you are using (or willing to use) Spring Boot then you can use the @ConfigurationProperties annotation.

Here is an example from the Spring Boot source code:

@ConfigurationProperties(prefix = "spring.activemq")
public class ActiveMQProperties {

    private String brokerUrl = "tcp://localhost:61616";

    private boolean inMemory = true;

    private boolean pooled = false;

    private String user;

    private String password;

    // Will override brokerURL if inMemory is set to true
    public String getBrokerUrl() {
        if (this.inMemory) {
            return "vm://localhost";
        }
        return this.brokerUrl;
    }

    public void setBrokerUrl(String brokerUrl) {
        this.brokerUrl = brokerUrl;
    }

    public boolean isInMemory() {
        return this.inMemory;
    }

    public void setInMemory(boolean inMemory) {
        this.inMemory = inMemory;
    }

    public boolean isPooled() {
        return this.pooled;
    }

    public void setPooled(boolean pooled) {
        this.pooled = pooled;
    }

    public String getUser() {
        return this.user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

}

Effectively what this does is map the properties spring.activemq.* to their respective properties.

Using the previous kind of code spares you from needed to use @Value on each field.

For the specific DataSource example you are showing, Spring Boot as of version 1.1.0.M1 provides the DataSourceBuilder which build on @ConfigurationProperties and vastly simplifies the kind of configuration you are trying to achieve. See the documentation here

In your case the code would be:

@Bean
@ConfigurationProperties(prefix="txn")
public DataSource primaryDataSource() {
    return DataSourceBuilder.create().build();
}

@Bean
@ConfigurationProperties(prefix="rpt")
public DataSource secondaryDataSource() {
    return DataSourceBuilder.create().build();
}