Spring and Strategy Pattern

1: Definition of Strategy Pattern

The strategy pattern is a packaging of the algorithm, which separates the responsibility of using the algorithm from the algorithm itself and delegates it to different object management. The strategy pattern usually packages a series of algorithms into a series of strategy classes, as a subclass of an abstract strategy class.

The class diagram is as follows:

If the strategy pattern is to be implemented using JAVA classes, the source code is as follows:

Java code

/** 
 * 
 * 策略执行 
 * @author weique.lqf 
 * @version $Id: Context.java, v 0.1 2014-2-9 下午2:32:56 weique.lqf Exp $ 
 */  
public class Context {  
    private Strategy stg;  
   
    public Context(Strategy theStg) {  
        this.stg = theStg;  
    }  
   
    public void doAction() {  
        this.stg.testStrategy();  
    }  
}

Strategy interface:

Java代码  
/** 
 * 
 * 
 * @author weique.lqf 
 * @version $Id: Strategy.java, v 0.1 2014-2-9 下午2:32:17 weique.lqf Exp $ 
 */  
public interface Strategy {  
   
    void testStrategy();  
}

Implementation class one :

Java code

package com.proxy.strategy.impl;  
   
import com.proxy.strategy.Strategy;  
   
public class PrintStrategy implements Strategy {  
   
    public void testStrategy() {  
        System.out.print("我要打印！！");  
    }  
   
}

Implementation category two:

Java code

package com.proxy.strategy.impl;  
   
import com.proxy.strategy.Strategy;  
   
public class WriteStrategy implements Strategy {  
   
    public void testStrategy() {  
        System.out.println("我要写字！！！");  
    }  
   
}

Execution code:

Java code

package com.proxy.strategy;  
   
import com.proxy.strategy.impl.PrintStrategy;  
   
public class StrategyClient {  
   
    public static void main(String[] args) {  
        Strategy stgA = new PrintStrategy();  
        Context ct = new Context(stgA);  
        ct.doAction();  
    }  
}

Two: spring implementation strategy pattern

Now The system using spring can There are so many, so how to implement strategies in spring mode?

In fact, it only needs a little modification, because one of the cores of spring is IOC.

First modify the Contex class:

Java code

package com.proxy.strategy;  
public class ContextSpring {  
    private Strategy stg;  
   
    /** 
     * Setter method for property <tt>stg</tt>. 
     * 
     * @param stg value to be assigned to property stg 
     */  
    public void setStg(Strategy stg) {  
        this.stg = stg;  
    }  
   
    public void doAction() {  
        this.stg.testStrategy();  
    }  
}

Then configure it in the spring configuration file,

Xml code

<bean id="ct" class = "com.proxy.strategy.ContextSpring">  
      <property name="stg" ref="writeStg"/>  
   </bean>  
   <bean id="writeStg" class = "com.proxy.strategy.impl.WriteStrategy"/>  
   <bean id="printStg" class = "com.proxy.strategy.impl.PrintStrategy"/>

Select the implementation class you want to inject, and then write this in the executed code :

Java code

package com.proxy.strategy;  
import org.springframework.context.ApplicationContext;  
import org.springframework.context.support.ClassPathXmlApplicationContext;  
   
public class StrategySpringClient {  
   
    public static void main(String[] args) {  
        ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");  
        ContextSpring ct = (ContextSpring) context.getBean("ct");  
        ct.doAction();  
    }  
}

Look, spring is introduced in this way.

But this has advantages and disadvantages. If I want to apply according to different types, for example: contracts need to be printed, while love letters need to be handwritten. Assuming that the contract is type 2 and the love letter is type 1, how do we automatically adapt?

Three: Advanced version of spring strategy mode

First modify the Context class:

Java code

package com.proxy.strategy;  
import java.util.HashMap;  
import java.util.Map;    
/** 
 * 
 * 
 * @author weique.lqf 
 * @version $Id: ContextSpringFactory.java, v 0.1 2014-2-9 下午3:46:09 weique.lqf Exp $ 
 */  
public class ContextSpringFactory {  
    private Map<String, Strategy> stgMap = new HashMap<String, Strategy>();  
    /** 
     * Getter method for property <tt>stgMap</tt>. 
     * 
     * @return property value of stgMap 
     */  
    public Map<String, Strategy> getStgMap() {  
        return stgMap;  
    }  
    /** 
     * Setter method for property <tt>stgMap</tt>. 
     * 
     * @param stgMap value to be assigned to property stgMap 
     */  
    public void setStgMap(Map<String, Strategy> stgMap) {  
        this.stgMap = stgMap;  
    }  
    public void doAction(String strType) {  
        this.stgMap.get(strType).testStrategy();  
    }  
}

Then modify the spring configuration file:

Xml code

<bean id="ctf" class = "com.proxy.strategy.ContextSpringFactory">  
      <property name="stgMap">   
         <map>   
              <entry key="1" value-ref="writeStg"/>   
              <entry key="2" value-ref="printStg"/>    
         </map>   
      </property>   
   </bean>

The entry class modification performed For:

Java code

package com.proxy.strategy;  
import org.springframework.context.ApplicationContext;  
import org.springframework.context.support.ClassPathXmlApplicationContext;  
public class StrategySpringClientFactory {  
    public static void main(String[] args) {  
        //外部参数  
        String type = "1";  
        ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");  
        ContextSpringFactory ctf = (ContextSpringFactory) context.getBean("ctf");  
        ctf.doAction(type);  
        //type 2  
        type = "2";  
        ctf.doAction(type);  
    }  
}

Then run it and see what the results will be?