[FIXED] Spring injection Into Servlet

Issue

So I have seen this question:

Spring dependency injection to other instance

and was wondering if my method will work out.

1) Declare beans in my Spring application context

    <bean id="dataSource" destroy-method="close" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="driverClassName" value="${jdbc.driverClassName}"/>
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
        <property name="initialSize" value="${jdbc.initialSize}" />
        <property name="validationQuery" value="${jdbc.validationQuery}" /> 
        <property name="testOnBorrow" value="${jdbc.testOnBorrow}" />
    </bean>

    <bean id="apiData" class="com.mydomain.api.data.ApiData">
        <property name="dataSource" ref="dataSource" />
        <property name="apiLogger" ref="apiLogger" />
    </bean>

    <bean id="apiLogging" class="com.mydomain.api.data.ApiLogger">
        <property name="dataSource" ref="dataSource" />
    </bean>

2) Override my servlet's init method as shown:

    @Override
    public void init(ServletConfig config) throws ServletException {
       super.init(config);

       ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

       this.apiData = (ApiData)ac.getBean("apiData");
       this.apiLogger = (ApiLogger)ac.getBean("apiLogger");
    }

Will this work or is Spring not yet ready to deliver beans to my servlet at this point in the web applications deployment? Do I have to do something more traditional like putting the beans in web.xml?

Solution

What you are trying to do will make every Servlet have its own ApplicationContext instance. Maybe this is what you want, but I doubt it. An ApplicationContext should be unique to an application.

The appropriate way to do this is to setup your ApplicationContext in a ServletContextListener.

public class SpringApplicationContextListener implements ServletContextListener {
        @Override
    public void contextInitialized(ServletContextEvent sce) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

        sce.getServletContext().setAttribute("applicationContext", ac);            
    }
    ... // contextDestroyed
}

Now all your servlets have access to the same ApplicationContext through the ServletContext attributes.

@Override
public void init(ServletConfig config) throws ServletException {
   super.init(config);

   ApplicationContext ac = (ApplicationContext) config.getServletContext().getAttribute("applicationContext");

   this.apiData = (ApiData)ac.getBean("apiData");
   this.apiLogger = (ApiLogger)ac.getBean("apiLogger");
}

Answered By - Sotirios Delimanolis