Join the social network of Tech Nerds, increase skill rank, get work, manage projects...
 
  • How to use Filters to Customize Scanning?

    • 0
    • 1
    • 0
    • 2
    • 0
    • 0
    • 0
    • 0
    • 265
    Comment on it

    In Spring context XML file, Filter has a sub-element 'context:include-filter' having two attributes as 'type' and 'expression' attributes that indicate to Spring container that 'type' is of regular expression whose value is been provided by expression attribute. By this concept Spring gets to know that which classes are to be scanned and treated as bean.

    1. Filter component include

    Use the below example to see how we use Spring filtering to scan and register components name which matched defined regex, even the class is not annotated with @Component.

    DAO layer

    Define the DAO class as below:

    EmployeeDAO.java

    package com.example.employee.dao;
    
    public class EmployeeDAO 
    {
        @Override
        public String toString() {
            return "Hello , We are in EmployeeDAO";
        }   
    }
    

    Service layer

    Define Service class as below:

    EmployeeService.java

    package com.example.employee.services;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import com.example.employee.dao.EmployeeDAO;
    
    public class EmployeeService 
    {
        @Autowired
        EmployeeDAO employeeDAO;
    
        @Override
        public String toString() {
            return "EmployeeService [employeeDAO=" + employeeDAO + "]";
        }
    
    }
    

    Spring filtering.

    Now define the below code in app-context.xml

    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-2.5.xsd">
    
        <context:component-scan base-package="com.example" >
    
            <context:include-filter type="regex" 
                           expression="com.example.employee.dao.*DAO.*" />
    
            <context:include-filter type="regex" 
                           expression="com.example.employee.services.*Service.*" />
    
        </context:component-scan>
    
    </beans>
    

    Now define the below class to run the code:

    App.java

    package com.example.common;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.example.employee.services.EmployeeService;
    
    public class App 
    {
        public static void main( String[] args )
        {
            ApplicationContext context = 
            new ClassPathXmlApplicationContext(new String[] {"app-context.xml"});
    
            EmployeeService emp = (EmployeeService)context.getBean("employeeService");
            System.out.println(emp);
    
        }
    }
    

    Output

    EmployeeService [employeeDAO=Hello , This is EmployeeDAO]
    

    In this XML filtering, all filess name contains DAO or Service (DAO., Services.) word will be detected and registered in Spring container.

    2. Filter component exclude

    You can also exclude specified components, to avoid Spring to detect and register it in Spring container. For this define the below code in your app-context.xml

    Exclude those files name contains DAO word.

    <?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:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    
       <context:annotation-config/>
    
        <context:component-scan base-package="com.example" >
        <context:exclude-filter type="regex" 
            expression="com.example.employee.dao.*DAO.*" />     
    </context:component-scan>
    </beans>
    

    Hope this will help you:)

 0 Comment(s)

Sign In
                           OR                           
                           OR                           
Register

Sign up using

                           OR                           
Forgot Password
Fill out the form below and instructions to reset your password will be emailed to you:
Reset Password
Fill out the form below and reset your password: