gistfile1.java

interface DataSource {
	
	public String getData();
	
}

class RestDataSource implements DataSource {
	...
}

class SqlDataSource implements DataSource {
	...
}

class Parser {
	
	private DataSource dataSource;
	
	public Parser() {
	}
	
	public void setDataSource(DataSource dataSource) {
		this.dataSource = dataSource;
	}
	
	public void parse() {
		String source = dataSource.getData();
		doParse(source);
	}
}

Parser parser = new Parser();
parser.setDataSource(new RestDataSource("file://tmp/forparse.txt"));
parser.parse();

parser.setDataSource(new SqlDataSource("mysql:user@localhost/db/schema/table/?=SELECT forparse FROM source"));
parser.parse();