Spring 3 annotations

Spring 3 annotations

context:property-placeholder:
====================

This configuration is used to configure property placeholders
and one or more locations can be provided with a comma-separated
list in the location attribute.


Example:

<context:property-placeholder location="classpath:com/xyz/jdbc.properties"/>


<context-annotation-config/>
===================

This configuration looks for annotations on beans in the application context & only inspects for Auto-wired beans in your controllers.

context:component-scan

=================

This configuration scans beans for @Controller, @Service, @Repository etc in base-package annotated classes.

Example single base package:
<context:component-scan base-package="com.xyz"/>



Example multiple base packages:
<context:component-scan base-package="com.xyz,com.abc,..  ."/>


base-package is comman parent package for @Controller, @Service, @Repository etc.


context:include-filter & context:exclude-filter:


These are chaild tags for “context:component-scan” you can include & discard classes scan beans. 


Example:


<context:component-scan base-package="org.example">
    <context:include-filter type="regex" expression=".*xyx.*Service"/>
    <context:exclude-filter type="annotation" expression="com.xyz.Repository"/>
</context:component-scan>



@Controller:
============


Class which is annotated with it acts as spring controller

@RequestMapping
=================
This annotation maps web requests onto specific controller classes
and/or  methods of it.

@Controller
@RequestMapping("hello") – maps to controller class
public class HelloController
{
@RequestMapping(value ="/welcome", method =
RequestMethod.GET) – maps to specific method of controller class
        public String welcome(Model model) {

         --------
        }       
}

@RequestParam
=============
This annotation is used to bind request parameters to a method parameter
in controllers.

Example:
========
public String addEmp(@RequestParam("empId") int empId,

@RequestParam("empName") String empName, ModelMap model) {-----}

@Scope:
=======
This annotation is used to specify scope of the beans.

Example:
@Scope("request"), @Scope("prototype")

@Service
========
Class which is annotated with it acts as service class(Contains bussiness logic).

@Repository:
============
Class which is annotated with it acts as DAO class(Contains Data Access Object
-JDBC logic).

@Component:
===========
This annotation is used generic spring mannaged component.

@Resource:
==========
This annotation is used on bean fileds/setter-methods and it have name attribute.
Spring interprets the name and injects specified bean.

@Qualifier
=========
This annotation gives more control over the selection process of bean
and allows for associating qualifier values with specific arguments.
It removes ambiguity in bean wiring with auto-wire.
It narrows the set of type matches so that assigns specific bean.

Example:

@Autowired
@Qualifier("searchService ")
private SearchServiceImpl searchService;


@Required:
==========
This annotation is used to appliy on bean properties/setter-methods.
Particular property/setter-methods of class must be provided
otherwise the configuration fails.

Example:

@Required
public void setEmployee(Employee emp)
{
   this. emp = emp;
}

@PathVariable:
==============
This annotation is used on a spring controller method argument to bind it
to the value of a URI template variable.

Example:

@RequestMapping(value="/employees/{empId}", method=RequestMethod.GET)
 public String findEmp(@PathVariable String empId, Model model) { 
 Employee emp = empService.findEmo(empId); 
 ---------
}

@Value
======
This annotation is used to inject value of member variable from property file.

Example
  private @Value("#{jdbcProperties.url}") String jdbcUrl;
  private @Value("#{jdbcProperties.username}") String username;
  private @Value("#{jdbcProperties.password}") String password;


@PostConstruct and @PreDestroy
=================================
These annotations offers initialization callbacks and destruction callbacks.

 Example:

Class MyDataSource {  
 Connection con = null;  
 @PostConstruct
 public Connection getConnction() {
       ----------  
 }      

 @PreDestroy   
 public void clearConnection () { 
      -----------  
 }
}


@ModelAttribute:
================
This annotation binds a method parameter or method return value to a named model attribute.

Example:
Binding a method parameter:

@RequestMapping(method = RequestMethod.POST)
public String processSubmit(@ModelAttribute("employee") Employee employee,
               BindingResult result, SessionStatus status) {
        --------
}

Binding a method return value:
@ModelAttribute("booksList")
public List<String> populateBooksListList() {
        List<String> booksList = new ArrayList<String>();
        booksList.add("Spring MVC");
        booksList.add("Oracle");
        booksList.add("Java");
        booksList.add("JSF");
        return booksList;
}