Annotation based ServiceLocatorFactoryBean?

Question

I would like to implement Factory pattern in my project..i have gone through online resources and I came to know that spring ServiceLocatorFactoryBean should be implemented instead of normal java factory pattern....

i have followed this link but it is explained in xml based....can any one tell me how to do it using annotations based Factory pattern??

Answer 1

Spring Java Configuration ref guide @Configuration

Interface Parser.class

public interface Parser {
  void parse(String str);
}

Implementation for above interface.

JsonParser.java

public class JsonParser implements Parser {
  @Override
  public void parse(String str) {
     System.out.println("JsonParser.parse::" + str);
  }
}

XMLParser.java

public class XMLParser implements Parser{

  @Override
  public void parse(String str) {
     System.out.println("XMLParser.parse :: " + str);
  }
}

ParserFactory.java actual Factory interface.

public interface ParserFactory {
  public Parser getParser(ParserType parserType);
}

ParseType.java enum to specify parsing types(avoid typos and safe)

public enum ParserType {

JSON("jsonParser"), XML("xmlParser");

private final String value;

  ParserType(String input) {
     this.value = input;
  }

  public String getValue() {
     return this.value;
  }

  @Override
  public String toString() {
    return this.value;
  }
}

ParseService.java , where Business logic implemeted.

@Service
public class ParserService {

 @Autowired
 private ParserFactory parserFactory;

 public void doParse(String parseString, ParserType parseType) {
    Parser parser = parserFactory.getParser(parseType);
    System.out.println("ParserService.doParse.." + parser);
    parser.parse(parseString);
 }
}

Finally AppConfig.java Spring java configuration class, where all of my beans registered as container managed beans.

@Configuration
@ComponentScan(basePackages = {"<Your Package Name>"})
public class AppConfig {
 @Bean
 public FactoryBean serviceLocatorFactoryBean() {
    ServiceLocatorFactoryBean factoryBean = new ServiceLocatorFactoryBean();
    factoryBean.setServiceLocatorInterface(ParserFactory.class);
    return factoryBean;
 }

 @Bean(name = "jsonParser")
 @Scope(scopeName = ConfigurableBeanFactory.SCOPE_PROTOTYPE)
 public JsonParser jsonParser() {
    return new JsonParser();
 }

 @Bean(name = "xmlParser")
 @Scope(scopeName = ConfigurableBeanFactory.SCOPE_PROTOTYPE)
 public XMLParser xmlParser() {
    return new XMLParser();
 }
}

Now autowire ParserService bean in either controller or test classs, and invoke parese(String, ParseType) method to test.

Here is my test.

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = AppConfig.class)
public class ServiceLocatorFactoryExample {


 @Autowired
 private ParserService parserService;

 @Test
 public void testParserFactory() {
    parserService.doParse("Srilekha", ParserType.JSON);
    parserService.doParse("Srilekha", ParserType.XML);
 }
}