Below diagram will make it clear:
For example:
1.Country.java:
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package org.arpit.java2blog; public class Country { String countryName; Capital capitalObj; public String getCountryName() { return countryName; } public void setCountryName(String countryName) { this.countryName = countryName; } public Capital getCapitalObj() { return capitalObj; } public void setCapitalObj(Capital capitalObj) { this.capitalObj = capitalObj; } } |
2.Capital.java
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package org.arpit.java2blog; public class Capital { String capitalName; public String getCapitalName() { return capitalName; } public void setCapitalName(String capitalName) { this.capitalName = capitalName; } } |
3.BeanAutowiringByTypeMain.java
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package org.arpit.javapostsforlearning; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class BeanAutowiringByTypeMain{ 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.getCapitalObj().getCapitalName(); System.out.println(capitalName+" is capital of "+countryName); } } |
4.ApplicationContext.xml
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<?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.java2blog.Country" autowire="byType"> <property name="countryName" value="India"/> </bean> <bean id="capital" class="org.arpit.java2blog.Capital"> <property name="capitalName" value="Delhi" /> </bean> </beans> |
Here in ,we have used autowire attribute and set it to “byType”.So now spring container will match Capital datatype in Country class with type of other beans in XML configuration file. So here you can see we have bean with class as Capital.
5.Run it
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Delhi is capital of India |
What if two properties of class have same datatype:
Change ApplicationContext.xml as below:
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<?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.java2blog.Country" autowire="byType"> <property name="countryName" value="India"/> </bean> <bean id="capital1" class="org.arpit.java2blog.Capital"> <property name="capitalName" value="Delhi1" /> </bean> <bean id="capital2" class="org.arpit.java2blog.Capital"> <property name="capitalName" value="Delhi2" /> </bean> </beans> |
In above xml, we have declared two capital beans,now how it will autowire.
Answer: It won’t.
When you run above program, it will give you below exception:
It will give you below exception.