This is a big topic. The Spring reference doc devotes multiple chapters to it. I recommend reading the ones on Aspect-Oriented Programming and Transactions, as Spring's declarative transaction support uses AOP at its foundation.
But at a very high level, Spring creates proxies for classes that declare @Transactional
on the class itself or on members. The proxy is mostly invisible at runtime. It provides a way for Spring to inject behaviors before, after, or around method calls into the object being proxied. Transaction management is just one example of the behaviors that can be hooked in. Security checks are another. And you can provide your own, too, for things like logging. So when you annotate a method with @Transactional
, Spring dynamically creates a proxy that implements the same interface(s) as the class you're annotating. And when clients make calls into your object, the calls are intercepted and the behaviors injected via the proxy mechanism.
Transactions in EJB work similarly, by the way.
As you observed, through, the proxy mechanism only works when calls come in from some external object. When you make an internal call within the object, you're really making a call through the this
reference, which bypasses the proxy. There are ways of working around that problem, however. I explain one approach in this forum post in which I use a BeanFactoryPostProcessor
to inject an instance of the proxy into "self-referencing" classes at runtime. I save this reference to a member variable called me
. Then if I need to make internal calls that require a change in the transaction status of the thread, I direct the call through the proxy (e.g. me.someMethod()
.) The forum post explains in more detail.
Note that the BeanFactoryPostProcessor
code would be a little different now, as it was written back in the Spring 1.x timeframe. But hopefully it gives you an idea. I have an updated version that I could probably make available.
Since I spent a lot of time on this issue, I thought I'd share my solution. Since spring 3.0.4, there is a configuration parameter that is called <mvc:resources/>
(more about that on the reference documentation website) which can be used to serve static resources while still using the DispatchServlet on your site's root.
In order to use this, use a directory structure that looks like the following:
src/
springmvc/
web/
MyController.java
WebContent/
resources/
img/
image.jpg
WEB-INF/
jsp/
index.jsp
web.xml
springmvc-servlet.xml
The contents of the files should look like:
src/springmvc/web/HelloWorldController.java:
package springmvc.web;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class HelloWorldController {
@RequestMapping(value="/")
public String index() {
return "index";
}
}
WebContent/WEB-INF/web.xml:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
WebContent/WEB-INF/springmvc-servlet.xml:
<?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"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<!-- not strictly necessary for this example, but still useful, see http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/mvc.html#mvc-ann-controller for more information -->
<context:component-scan base-package="springmvc.web" />
<!-- the mvc resources tag does the magic -->
<mvc:resources mapping="/resources/**" location="/resources/" />
<!-- also add the following beans to get rid of some exceptions -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />
<bean
class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
</bean>
<!-- JSTL resolver -->
<bean id="viewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>
</beans>
WebContent/jsp/index.jsp:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<h1>Page with image</h1>
<!-- use c:url to get the correct absolute path -->
<img src="<c:url value="/resources/img/image.jpg" />" />
Hope this helps :-)
Best Solution
Read this : Validation...
However you must implement the Validation interface in a class, and than use it to validate your object, and to do that you autowire validator in your controller..
This is an example:
and in your controller: