injecting Value in Spring always null

I am following this tutorial but and when trying to run the application it runs with this error stack

    Jul 18, 2014 3:45:23 AM org.springframework.context.support.FileSystemXmlApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.FileSystemXmlApplicationContext@1f2f0ce9: display name [org.springframework.context.support.FileSystemXmlApplicationContext@1f2f0ce9]; startup date [Fri Jul 18 03:45:23 EEST 2014]; root of context hierarchy
Jul 18, 2014 3:45:23 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from file [C:\Users\Yasha\workspace3\Test\spring-beans.xml]
Jul 18, 2014 3:45:23 AM org.springframework.context.support.FileSystemXmlApplicationContext obtainFreshBeanFactory
INFO: Bean factory for application context [org.springframework.context.support.FileSystemXmlApplicationContext@1f2f0ce9]: org.springframework.beans.factory.support.DefaultListableBeanFactory@1ba22e94
Jul 18, 2014 3:45:23 AM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1ba22e94: defining beans [itemBean,customerBean]; root of factory hierarchy
Jul 18, 2014 3:45:24 AM org.springframework.beans.factory.support.DefaultListableBeanFactory destroySingletons
INFO: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1ba22e94: defining beans [itemBean,customerBean]; root of factory hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'customerBean' defined in file [C:\Users\Yasha\workspace3\Test\spring-beans.xml]: Cannot resolve reference to bean '#{itemBean}' while setting bean property 'item'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named '#{itemBean}' is defined
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:275)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1245)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:140)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:84)
    at SpringEl.app.main(app.java:8)
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named '#{itemBean}' is defined
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:387)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:971)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:246)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269)
    ... 18 more

What I am doing wrong here ?

I have simply followed the first step of this tutorial which is injecting value via XML

spring-beans.xml:

<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="itemBean" class="SpringEl.Item">
        <property name="name" value="itemA" />
        <property name="qty" value="10" />
    </bean>

    <bean id="customerBean" class="SpringEl.Customer">
        <property name="item" value="#{itemBean}" />
        <property name="itemName" value="#{itemBean.name}" />
    </bean>

</beans>

Customer.java:

package SpringEl;

public class Customer {

    private Item item;

    private String itemName;

    public Item getItem() {
        return item;
    }

    public void setItem(Item item) {
        this.item = item;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }

    @Override
    public String toString() {
        return "Customer [item=" + item + ", itemName=" + itemName + "]";
    }

}

Item.java:

package SpringEl;

public class Item {

    private String name;

    private int qty;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getQty() {
        return qty;
    }

    public void setQty(int qty) {
        this.qty = qty;
    }
}

and eventually my main class

app.java

   public class app {
        public static void main(String[] args) {
            ApplicationContext context = new FileSystemXmlApplicationContext("spring-beans.xml");


        Customer obj = (Customer) context.getBean("customerBean");
        System.out.println(obj);
    }
}

Solution

Make sure that the spring-context dependency is specified properly in the pom.xml file. Here is an example:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.stack.overflow</groupId>
    <artifactId>example</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>example</name>
    <description>example</description>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.0.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.0.6.RELEASE</version>
        </dependency>
    </dependencies>
</project>

The spring-context dependency has its own dependency on the spring-expression artifact, which is basically Spring EL.

My hunch is that Spring EL is not being placed on the classpath. So when the Spring IOC container begins to read the spring-beans.xml configuration file, it does not resolve the expression #{itemBean} and it treats the expression as a String literal. This causes an issues because the item property on the customerBean bean expects a type of SpringEl.Item as opposed to a String.

Fixing the dependency in the pom.xml file will place Spring EL on the classpath and allow the proper resolution of the expression to take place, ultimately satisfying the dependency with a bean of the proper type.