How to inject environmental variables inside spring xml configuration?

Question

AWS talks about System.getProperty(\"JDBC_CONNECTION_STRING\") in http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create_deploy_Java.managing.html after we s

Answer 1

For someone who use JavaConfig:

In @Configuration file we need to have:

@Bean 
public static PropertyPlaceholderConfigurer properties() {

    PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer();
    ClassPathResource[] resources = new ClassPathResource[ ] {
        new ClassPathResource("db.properties")
    };
    ppc.setLocations( resources );
    ppc.setIgnoreUnresolvablePlaceholders( true );
    ppc.setSearchSystemEnvironment(true);
    return ppc;
}

@Value("${db.url}")
private String dbUrl; 
@Value("${db.driver}")
private String dbDriver;
@Value("${db.username}")
private String dbUsername;
@Value("${db.password}")
private String dbPassword;

@Bean
public DataSource db() {

    BasicDataSource dataSource = new BasicDataSource();
    dataSource.setUrl(dbUrl);
    dataSource.setDriverClassName(dbDriver);
    dataSource.setUsername(dbUsername);
    dataSource.setPassword(dbPassword);
    return dataSource;
}

important is line: ppc.setSearchSystemEnvironment(true);

after that in db.properties, I have:

db.url = ${PG_URL}
db.driver = ${PG_DRIVER}
db.username = ${PG_USERNAME}
db.password = ${PG_PASSWORD}