Spring. Dependency Injection

     The client delegates to call to another object the responsibility of providing its dependencies.


<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd">

   <bean id="myFortune" class="com.example.demo.HappyFortuneService">
      
   </bean>

   <bean id = "myCoach" class="com.example.demo.TrackCoach">
      <constructor-arg ref="myFortune"/>
   </bean>

</beans>





package com.example.demo;

public class TrackCoach implements Coach {

    private FortuneService fortuneService;

    public TrackCoach(FortuneService fortuneService) {
        this.fortuneService = fortuneService;
    }

    @Override
    public String getDailyWorkout() {
        return "Run a hard 5k";
    }

    @Override
    public String getDailyFortune() {
        return "Just do it: " + fortuneService.getFortune();
    }
}
Setter Injection


<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd">

   <bean id="myFortune" class="com.example.demo.HappyFortuneService">
   </bean>

   <bean id = "myCoach" class="com.example.demo.BaseballCoach">
      <constructor-arg ref="myFortune"/>
   </bean>

   <bean id="myCricketCoach" class="com.example.demo.CricketCoach">
      <property name="fortuneService" ref="myFortune"/>
   </bean>

</beans>

package com.example.demo;

public class CricketCoach implements Coach{

    private FortuneService fortuneService;

    public CricketCoach() {
        System.out.println("CricketCoach: inside no-arg constructor");
    }

    public void setFortuneService(FortuneService fortuneService) {
        System.out.println("CricketCoach: inside setter method - setFortuneService");
        this.fortuneService = fortuneService;
    }

    @Override
    public String getDailyWorkout() {
        return "Practice fast bowling for 15 minutes";
    }

    @Override
    public String getDailyFortune() {
        return fortuneService.getFortune();
    }
}
package com.example.demo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SetterDemoApp {
    public static void main(String[] args) {

        // load the spring configuration file
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        // retrieve bean from spring container
        CricketCoach coach = context.getBean("myCricketCoach", CricketCoach.class);

        // call methods on the bean
        System.out.println(coach.getDailyWorkout());
        System.out.println(coach.getDailyFortune());

        // close the context
        context.close();
    }
}
Injecting Literal Values
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd">

   <bean id="myFortune" class="com.example.demo.HappyFortuneService">
   </bean>

   <bean id = "myCoach" class="com.example.demo.BaseballCoach">
      <constructor-arg ref="myFortune"/>
   </bean>

   <bean id="myCricketCoach" class="com.example.demo.CricketCoach">
      <property name="fortuneService" ref="myFortune"/>
      <property name="emailAddress" value="example@gmail.com"/>
      <property name="team" value="Tornado"/>
   </bean>

</beans>

package com.example.demo;

public class CricketCoach implements Coach {

    private FortuneService fortuneService;

    // add new fields for emailAddress and team
    private String emailAddress;
    private String team;

    public CricketCoach() {
        System.out.println("CricketCoach: inside no-arg constructor");
    }

    public void setFortuneService(FortuneService fortuneService) {
        System.out.println("CricketCoach: inside setter method - setFortuneService");
        this.fortuneService = fortuneService;
    }

    @Override
    public String getDailyWorkout() {
        return "Practice fast bowling for 15 minutes";
    }

    @Override
    public String getDailyFortune() {
        return fortuneService.getFortune();
    }

    public String getEmailAddress() {
        return emailAddress;
    }

    public void setEmailAddress(String emailAddress) {
        System.out.println("CricketCoach: inside setter method - setEmailAddress");
        this.emailAddress = emailAddress;
    }

    public String getTeam() {
        return team;
    }

    public void setTeam(String team) {
        System.out.println("CricketCoach: inside setter method - setTeam");
        this.team = team;
    }
}
package com.example.demo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SetterDemoApp {
    public static void main(String[] args) {

        // load the spring configuration file
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        // retrieve bean from spring container
        CricketCoach coach = context.getBean("myCricketCoach", CricketCoach.class);

        // call methods on the bean
        System.out.println(coach.getDailyWorkout());
        System.out.println(coach.getDailyFortune());
        System.out.println(coach.getEmailAddress());
        System.out.println(coach.getTeam());
        // close the context
        context.close();
    }
}
Injecting values from a Properties File
foo.emai=test@gmail.com
foo.team=Bastards
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd">

   <context:property-placeholder location="sport.properties"/>

   <bean id="myFortune" class="com.example.demo.HappyFortuneService">
   </bean>

   <bean id = "myCoach" class="com.example.demo.BaseballCoach">
      <constructor-arg ref="myFortune"/>
   </bean>

   <bean id="myCricketCoach" class="com.example.demo.CricketCoach">
      <property name="fortuneService" ref="myFortune"/>
      <property name="emailAddress" value="${foo.emai}"/>
      <property name="team" value="${foo.team}"/>
   </bean>

</beans>
All other classes the same.

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