This is 10 of 16 parts of tutorial series
Tutorial Content: Spring tutorial for beginners
You have learnt how to declare beans using the element and inject with using and elements in XML configuration file.
In Spring framework, you can wire beans automatically with auto-wiring feature. To enable it, just define the “autowire” attribute in .The Spring container can autowire relationships between collaborating beans without using and elements which helps cut down on the amount of XML configuration
|
|
<bean id="countryBean" class="org.arpit.javapostsforlearning.Country" autowire="byName"> |
Autowiring modes:
There are following autowiring modes which can be used to instruct Spring container to use autowiring for dependency injection.
no:
Default, no auto wiring, set it manually via “ref” attribute as we have done in dependency injection via settor method post.
byName:
Autowiring by property name. Spring container looks at the properties of the beans on which autowire attribute is set to byName in the XML configuration file and it tries to match it with name of bean in xml configuration file.
byType:
Autowiring by property datatype. Spring container looks at the properties of the beans on which autowire attribute is set to byType in the XML configuration file. It then tries to match and wire a property if its type matches with exactly one of the beans name in configuration file. If more than one such beans exists, a fatal exception is thrown.
contructor:
byType mode in constructor argument.
autodetect:
Spring first tries to wire using autowire by constructor, if it does not work, Spring tries to autowire by byType.
Example:
1.Country.java:
This is simple pojo class having some attributes so here country has name and object of Capital class.
Create Country.java under package org.arpit.javapostsforlearning.Copy following content into Country.java.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 |
package org.arpit.javapostsforlearning; public class Country { String countryName; Capital capital; public String getCountryName() { return countryName; } public void setCountryName(String countryName) { this.countryName = countryName; } public Capital getCapital() { return capital; } public void setCapital(Capital capital) { this.capital = capital; } } |
2.Capital.java
This is also simple pojo class having one attribute called “capitalName”.
Create Capital.java under package org.arpit.javapostsforlearning.java.Above Country class contains object of this class.Copy following content into Capital.java
|
|
package org.arpit.javapostsforlearning; public class Capital { String capitalName; public String getCapitalName() { return capitalName; } public void setCapitalName(String capitalName) { this.capitalName = capitalName; } } |
3.BeanAutowirngByNameMain.java
This class contains main function.Create BeanAutowiringByNameMain.java under package org.arpit.javapostsforlearning.Copy following content into BeanAutowiringByNameMain.java
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 |
package org.arpit.javapostsforlearning; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class BeanAutowiringByNameMain{ public static void main(String[] args) { ApplicationContext appContext = new ClassPathXmlApplicationContext("ApplicationContext.xml"); Country countryObj = (Country) appContext.getBean("country"); String countryName=countryObj.getCountryName(); String capitalName=countryObj.getCapital().getCapitalName(); System.out.println(capitalName+" is capital of "+countryName); } } |
You can note here that we have used ClassPathXmlApplicationContext for getting bean here.There are various ways for getting beans.In
hello world example we have used XmlBeanFactory for getting beans.
4.ApplicationContext.xml
|
|
<?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:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="country" class="org.arpit.javapostsforlearning.Country" autowire="byName"> <property name="countryName" value="India"/> </bean> <bean id="capital" class="org.arpit.javapostsforlearning.Capital"> <property name="capitalName" value="Delhi" /> </bean> </beans> |
Here in ,we have used autowire attribute and set it to “byName”.So now spring container will match “capital” reference in Country class with id or name of other beans in XML configuration file. So here you can see we have bean with id as “capital”
When you will run above application,you will get following as output.
