光子CI之旅

// AutomatedTellerMachine接口 
package org.cdi.advocacy;  

import java.math.BigDecimal;  
public interface AutomatedTellerMachine {
          public abstract void deposit(BigDecimal bd);  //存錢
          public abstract void withdraw(BigDecimal bd);  //取錢  
}

// ATMTransport接口 
package org.cdi.advocacy;  

public interface ATMTransport {
         public void communicateWithBank(byte[] datapacket); 
}

// AutomatedTellerMachineImpl類 
package org.cdi.advocacy;
 ... 
public class AutomatedTellerMachineImpl implements AutomatedTellerMachine {
          private ATMTransport transport;
          ...
         public void deposit(BigDecimal bd) {
                 System.out.println("deposit called");
                 transport.communicateWithBank(...);
         }
          public void withdraw(BigDecimal bd) {
                 System.out.println("withdraw called");
                 transport.communicateWithBank(...);
         }  
}

//StandardAtmTransport 
package org.cdi.advocacy;   

public class StandardAtmTransport implements ATMTransport {
          public void communicateWithBank(byte[] datapacket) {
                 System.out.println("communicating with bank via Standard transport");
                 ...
         }  
}

//SoapAtmTransport 
package org.cdi.advocacy;  

public class SoapAtmTransport implements ATMTransport {
          public void communicateWithBank(byte[] datapacket) {
                 System.out.println("communicating with bank via Soap transport");
                 ...
         }  
}

//JsonRestAtmTransport 
package org.cdi.advocacy;  
public class JsonRestAtmTransport implements ATMTransport {
          public void communicateWithBank(byte[] datapacket) {
                 System.out.println("communicating with bank via JSON REST transport");
         }  
}

// AtmMain: 不使用CDI, Spring或Guice的DI實現 
package org.cdi.advocacy;  

public class AtmMain {
          public void main (String[] args) {
                 AutomatedTellerMachine atm = new AutomatedTellerMachineImpl();
                 ATMTransport transport = new SoapAtmTransport();
                 /* Inject the transport. */
                 ((AutomatedTellerMachineImpl)atm).setTransport(transport);
                  atm.withdraw(new BigDecimal("10.00"));
                  atm.deposit(new BigDecimal("100.00"));
         }  
}

//不使用CDI, Spring或Guice的DI實現 : setTransport 
ATMTransport transport = new SimulationAtmTransport();
 ((AutomatedTellerMachineImpl)atm).setTransport(transport);

<beans xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation=" http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/beans_1_0.xsd">
  
</beans>

// AutomatedTellerMachineImpl使用@Inject注入一個transport 
package org.cdi.advocacy;
  ...  
import javax.inject.Inject;  
public class AutomatedTellerMachineImpl implements AutomatedTellerMachine {
          private ATMTransport transport;
          @Inject
         public void setTransport(ATMTransport transport) {
                 this.transport = transport;
         }
         ...  
}

//StandardAtmTransport使用注解@Default 
package org.cdi.advocacy;  

import javax.enterprise.inject.Default;  
@Default 
public class StandardAtmTransport implements ATMTransport {
     ...

//JsonRestAtmTransport使用注解@Alternative 
package org.cdi.advocacy;  

import javax.enterprise.inject.Alternative;  
@Alternative 
public class JsonRestAtmTransport implements ATMTransport {  ... }

// SoapAtmTransport使用注解@Alternative 
package org.cdi.advocacy;  
import javax.enterprise.inject.Alternative;  
@Alternative 
public class SoapAtmTransport implements ATMTransport {    ... }

//AutomatedTellerMachineImpl使用注解@Name [source,java] package org.cdi.advocacy;  import java.math.BigDecimal;  import javax.inject.Inject; import javax.inject.Named;  @Named("atm") public class AutomatedTellerMachineImpl implements AutomatedTellerMachine {        ...  }

//名字默認值 @Named public class AutomatedTellerMachineImpl implements AutomatedTellerMachine {        ...  }

// AtmMain通過名字查找atm 
package org.cdi.advocacy;  
...  
public class AtmMain {
          ...
         ...
          public static void main(String[] args) throws Exception {
                 AutomatedTellerMachine atm = (AutomatedTellerMachine) beanContainer
                                 .getBeanByName("atm");
                  atm.deposit(new BigDecimal("1.00"));
          }  
}

deposit called             
communicating with bank via Standard transport

//AtmMain通過類型查找atm 
package org.cdi.advocacy;
  ...  
public class AtmMain {
          ...
         ...
      public static void main(String[] args) throws Exception {
         AutomatedTellerMachine atm = beanContainer.getBeanByType(AutomatedTellerMachine.class);
         atm.deposit(new BigDecimal("1.00"));
     }  
}

Exception in thread "main" java.lang.ExceptionInInitializerError 
Caused by: javax.enterprise.inject.AmbiguousResolutionException: org.cdi.advocacy.AutomatedTellerMachineImpl.setTransport: 
Too many beans match, because they all have equal precedence. 
See the @Stereotype and <enable> tags to choose a precedence.  Beans:     
     ManagedBeanImpl[JsonRestAtmTransport, {@Default(), @Any()}]
     ManagedBeanImpl[SoapAtmTransport, {@Default(), @Any()}]
     ManagedBeanImpl[StandardAtmTransport, {@javax.enterprise.inject.Default(), @Any()}]
     ...