Category: Java

Spring DI – Collections Setter ”; Previous Next You have seen how to configure primitive data type using value attribute and object references using ref attribute of the <property> tag in your Bean configuration file. Both the cases deal with passing singular value to a bean. Now what if you want to pass plural values like Java Collection types such as List, Set, Map, and Properties. To handle the situation, Spring offers following types of collection configuration elements which are as follows − Sr.No Element & Description 1 <list> This helps in wiring ie injecting a list of values, allowing duplicates. 2 <set> This helps in wiring a set of values but without any duplicates. 3 <props> This can be used to inject a collection of name-value pairs where the name and value are both Strings. You can use either <list> or <set> to wire any implementation of java.util.Collection or an array. In this example, we”re showcasing passing direct values of the collection elements. Example The following example shows a class JavaCollection that is using collections as dependency injected using setters. Let”s update the project created in Spring DI – Create Project chapter. We”re adding following files − JavaCollection.java − A class containing a collections as dependency. MainApp.java − Main application to run and test. Here is the content of JavaCollection.java file − package com.tutorialspoint; import java.util.*; public class JavaCollection { List<String> addressList; Set<String> addressSet; Properties addressProp; // a setter method to set List public void setAddressList(List<String> addressList) { this.addressList = addressList; } // prints and returns all the elements of the list. public List<String> getAddressList() { System.out.println(“List Elements :” + addressList); return addressList; } // a setter method to set Set public void setAddressSet(Set<String> addressSet) { this.addressSet = addressSet; } // prints and returns all the elements of the Set. public Set<String> getAddressSet() { System.out.println(“Set Elements :” + addressSet); return addressSet; } // a setter method to set Property public void setAddressProp(Properties addressProp) { this.addressProp = addressProp; } // prints and returns all the elements of the Property. public Properties getAddressProp() { System.out.println(“Property Elements :” + addressProp); return addressProp; } } Following is the content of the MainApp.java file − package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext(“applicationcontext.xml”); JavaCollection jc=(JavaCollection)context.getBean(“javaCollection”); jc.getAddressList(); jc.getAddressSet(); jc.getAddressProp(); } } Following is the configuration file applicationcontext.xml which has configuration for all the type of collections − <?xml version = “1.0” encoding = “UTF-8”?> <beans xmlns = “http://www.springframework.org/schema/beans” xmlns:xsi = “http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation = “http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd”> <!– Definition for javaCollection –> <bean id = “javaCollection” class = “com.tutorialspoint.JavaCollection”> <!– results in a setAddressList(java.util.List) call –> <property name = “addressList”> <list> <value>INDIA</value> <value>JAPAN</value> <value>USA</value> <value>UK</value> </list> </property> <!– results in a setAddressSet(java.util.Set) call –> <property name = “addressSet”> <set> <value>INDIA</value> <value>JAPAN</value> <value>USA</value> <value>UK</value> </set> </property> <!– results in a setAddressProp(java.util.Properties) call –> <property name = “addressProp”> <props> <prop key = “one”>INDIA</prop> <prop key = “two”>JAPAN</prop> <prop key = “three”>USA</prop> <prop key = “four”>UK</prop> </props> </property> </bean> </beans> Output Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message − List Elements :[INDIA, JAPAN, USA, UK] Set Elements :[INDIA, JAPAN, USA, UK] Property Elements :{four=UK, one=INDIA, two=JAPAN, three=USA} Print Page Previous Next Advertisements ”;

Spring DI – Constructor-Based ”; Previous Next Constructor-Based DI is accomplished when the container invokes a class constructor with a number of arguments, each representing a dependency on the other class. Example The following example shows a class TextEditor that can only be dependency-injected with constructor injection. Let”s update the project created in Spring DI – Create Project chapter. We”re adding following files − TextEditor.java − A class containing a SpellChecker as dependency. SpellChecker.java − A dependency class. MainApp.java − Main application to run and test. Here is the content of TextEditor.java file − package com.tutorialspoint; public class TextEditor { private SpellChecker spellChecker; public TextEditor(SpellChecker spellChecker) { System.out.println(“Inside TextEditor constructor.” ); this.spellChecker = spellChecker; } public void spellCheck() { spellChecker.checkSpelling(); } } Following is the content of another dependent class file SpellChecker.java package com.tutorialspoint; public class SpellChecker { public SpellChecker(){ System.out.println(“Inside SpellChecker constructor.” ); } public void checkSpelling() { System.out.println(“Inside checkSpelling.” ); } } Following is the content of the MainApp.java file. package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext(“applicationcontext.xml”); TextEditor te = (TextEditor) context.getBean(“textEditor”); te.spellCheck(); } } Following is the configuration file applicationcontext.xml which has configuration for the constructor-based 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” xsi:schemaLocation = “http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd”> <!– Definition for textEditor bean –> <bean id = “textEditor” class = “com.tutorialspoint.TextEditor”> <constructor-arg ref = “spellChecker”/> </bean> <!– Definition for spellChecker bean –> <bean id = “spellChecker” class = “com.tutorialspoint.SpellChecker”></bean> </beans> Output Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message − Inside SpellChecker constructor. Inside TextEditor constructor. Inside checkSpelling. Print Page Previous Next Advertisements ”;

Spring DI – Map Ref Constructor ”; Previous Next You have seen how to configure primitive data type using value attribute and object references using ref attribute of the <property> tag in your Bean configuration file. Both the cases deal with passing singular value to a bean. Now what if you want to pass Map. In this example, we”re showcasing passing direct values of the Map using constructor injection. Example The following example shows a class JavaCollection that is using collections as dependency injected using constructor arguments. Let”s update the project created in Spring DI – Create Project chapter. We”re adding following files − Address.java − A class to be used as dependency. JavaCollection.java − A class containing a collections of dependencies. MainApp.java − Main application to run and test. Here is the content of Address.java file − package com.tutorialspoint; public class Address { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return name; } } Here is the content of JavaCollection.java file − package com.tutorialspoint; import java.util.*; public class JavaCollection { Map<String, Address> addressMap; public JavaCollection() {} public JavaCollection(Map<String, Address> addressMap) { this.addressMap = addressMap; } // a setter method to set Map public void setAddressMap(Map<String, Address> addressMap) { this.addressMap = addressMap; } // prints and returns all the elements of the Map. public Map<String, Address> getAddressMap() { System.out.println(“Map Elements :” + addressMap); return addressMap; } } Following is the content of the MainApp.java file − package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext(“applicationcontext.xml”); JavaCollection jc=(JavaCollection)context.getBean(“javaCollection”); jc.getAddressMap(); } } Following is the configuration file applicationcontext.xml which has configuration for all the type of collections − <?xml version = “1.0” encoding = “UTF-8”?> <beans xmlns = “http://www.springframework.org/schema/beans” xmlns:xsi = “http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation = “http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd”> <bean id = “address1” class = “com.tutorialspoint.Address”> <property name=”name” value=”INDIA”></property> </bean> <bean id = “address2” class = “com.tutorialspoint.Address”> <property name=”name” value=”JAPAN”></property> </bean> <bean id = “address3” class = “com.tutorialspoint.Address”> <property name=”name” value=”USA”></property> </bean> <bean id = “address4” class = “com.tutorialspoint.Address”> <property name=”name” value=”UK”></property> </bean> <bean id = “javaCollection” class = “com.tutorialspoint.JavaCollection”> <constructor-arg name = “addressMap”> <map> <entry key = “1” value-ref = “address1″/> <entry key = “2” value-ref = “address2″/> <entry key = “3” value-ref = “address3″/> <entry key = “4” value-ref = “address4″/> </map> </constructor-arg> </bean> </beans> Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message − Map Elements :{1=INDIA, 2=JAPAN, 3=USA, 4=UK} Print Page Previous Next Advertisements ”;

Spring DI – Injecting Collections Constructor ”; Previous Next You have seen how to configure primitive data type using value attribute and object references using ref attribute of the <property> tag in your Bean configuration file. Both the cases deal with passing singular value to a bean. Now what if you want to pass plural values like Java Collection types such as List, Set, and Properties. To handle the situation, Spring offers following types of collection configuration elements which are as follows − Sr.No Element & Description 1 <list> This helps in wiring ie injecting a list of values, allowing duplicates. 2 <set> This helps in wiring a set of values but without any duplicates. 3 <props> This can be used to inject a collection of name-value pairs where the name and value are both Strings. You can use either <list> or <set> to wire any implementation of java.util.Collection or an array. In this example, we”re showcasing passing direct values of the collection elements. Example The following example shows a class JavaCollection that is using collections as dependency injected using constructor arguments. Let”s update the project created in Spring DI – Create Project chapter. We”re adding following files − JavaCollection.java − A class containing a collections as dependency. MainApp.java − Main application to run and test. Here is the content of JavaCollection.java file − package com.tutorialspoint; import java.util.*; public class JavaCollection { List<String> addressList; Set<String> addressSet; Properties addressProp; public JavaCollection() {} public JavaCollection(List<String> addressList, Set<String> addressSet, Properties addressProp) { this.addressList = addressList; this.addressSet = addressSet; this.addressProp = addressProp; } // a setter method to set List public void setAddressList(List<String> addressList) { this.addressList = addressList; } // prints and returns all the elements of the list. public List<String> getAddressList() { System.out.println(“List Elements :” + addressList); return addressList; } // a setter method to set Set public void setAddressSet(Set<String> addressSet) { this.addressSet = addressSet; } // prints and returns all the elements of the Set. public Set<String> getAddressSet() { System.out.println(“Set Elements :” + addressSet); return addressSet; } // a setter method to set Property public void setAddressProp(Properties addressProp) { this.addressProp = addressProp; } // prints and returns all the elements of the Property. public Properties getAddressProp() { System.out.println(“Property Elements :” + addressProp); return addressProp; } } Following is the content of the MainApp.java file − package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext(“applicationcontext.xml”); JavaCollection jc=(JavaCollection)context.getBean(“javaCollection”); jc.getAddressList(); jc.getAddressSet(); jc.getAddressProp(); } } Following is the configuration file applicationcontext.xml which has configuration for all the type of collections − <?xml version = “1.0” encoding = “UTF-8”?> <beans xmlns = “http://www.springframework.org/schema/beans” xmlns:xsi = “http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation = “http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd”> <bean id = “javaCollection” class = “com.tutorialspoint.JavaCollection”> <constructor-arg name = “addressList”> <list> <value>INDIA</value> <value>JAPAN</value> <value>USA</value> <value>UK</value> </list> </constructor-arg> <constructor-arg name = “addressSet”> <set> <value>INDIA</value> <value>JAPAN</value> <value>USA</value> <value>UK</value> </set> </constructor-arg> <constructor-arg name = “addressProp”> <props> <prop key = “one”>INDIA</prop> <prop key = “two”>JAPAN</prop> <prop key = “three”>USA</prop> <prop key = “four”>UK</prop> </props> </constructor-arg> </bean> </beans> Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message − List Elements :[INDIA, JAPAN, USA, UK] Set Elements :[INDIA, JAPAN, USA, UK] Property Elements :{four=UK, one=INDIA, two=JAPAN, three=USA} Print Page Previous Next Advertisements ”;

Spring DI – Static Factory ”; Previous Next Spring provides an option to inject dependency using factory-method attribute. Example The following example shows a class TextEditor that can only be dependency-injected using pure setter-based injection. Let”s update the project created in Spring DI – Create Project chapter. We”re adding following files − TextEditor.java − A class containing a SpellChecker as dependency. SpellChecker.java − A dependency class. MainApp.java − Main application to run and test. Here is the content of TextEditor.java file − package com.tutorialspoint; public class TextEditor { private SpellChecker spellChecker; private String name; public void setSpellChecker( SpellChecker spellChecker ){ this.spellChecker = spellChecker; } public SpellChecker getSpellChecker() { return spellChecker; } public void setName(String name) { this.name = name; } public String getName() { return name; } public void spellCheck() { spellChecker.checkSpelling(); } } Following is the content of another dependent class file SpellChecker.java − This class constructor is private. So its object can not be created directly using new operator by other object. It has a static factory method to get an instance. package com.tutorialspoint; public class SpellChecker { private SpellChecker(){ System.out.println(“Inside SpellChecker constructor.” ); } public static SpellChecker getInstance() { System.out.println(“Inside SpellChecker getInstance.” ); return new SpellChecker(); } public void checkSpelling(){ System.out.println(“Inside checkSpelling.” ); } } Following is the content of the MainApp.java file − package com.tutorialspoint; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext(“applicationcontext.xml”); TextEditor te = (TextEditor) context.getBean(“textEditor”); te.spellCheck(); } } Following is the configuration file applicationcontext.xml which has configuration for autowiring byName − <?xml version = “1.0” encoding = “UTF-8”?> <beans xmlns = “http://www.springframework.org/schema/beans” xmlns:xsi = “http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation = “http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd”> <!– Definition for textEditor bean –> <bean id = “textEditor” class = “com.tutorialspoint.TextEditor” autowire = “byName”> <property name = “name” value = “Generic Text Editor” /> </bean> <!– Definition for spellChecker bean –> <bean id = “spellChecker” class = “com.tutorialspoint.SpellChecker” factory-method=”getInstance”></bean> </beans> Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message − Inside SpellChecker getInstance. Inside SpellChecker constructor. Inside checkSpelling. Print Page Previous Next Advertisements ”;