Creating a custom view resolver in Spring MVC: Property 'url' is required

Question

I'm trying create a simple view resolver that returns hello world regardless of what view you want (as a starting point).

I have this so far:

public class MyViewResolver extends AbstractTemplateView {

    @Override
    protected void renderMergedTemplateModel(Map<String, Object> model, HttpServletRequest request,
                                             HttpServletResponse response) throws Exception {

        doRender(model, request, response);
    }

    protected void doRender(Map<String,Object> model, HttpServletRequest request, HttpServletResponse response)
            throws Exception {


        PrintWriter writer = response.getWriter();
        writer.write("hi from my resolver!");

    }


}

Now I am getting this error:

2012-03-29 16:51:28.855:WARN:/:unavailable
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'viewResolver' defined in ServletContext resource [/WEB-INF/application-context.xml]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Property 'url' is required
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1455)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)

I have implemented whatever the AbstractTemplateView required, not sure what url property it is asking for?

Also, where is the name of the view that is passed to this viewresolver?

Update

So I added:

 @Override
    public boolean isUrlRequired() {
        return false;
    }

And now I am just getting an error like:

HTTP ERROR 404

Problem accessing /home/index. Reason:

    NOT_FOUND

My application-context.xml has:

<bean id="viewResolver" class="com.example.MyViewResolver">

</bean>

What am I missing something?

Answer 1

You extend (indirectly) AbstractUrlBasedViewResolver, so it's logical that a URL is required to resolve the view. However, if in your case it is not required, you can override the isUrlRequired() method and return false

Answer 2

You have mixed up two concepts in Spring MVC. In Spring MVC you need both a view resolver and a view.

In your question you want two things:

• A view that returns "hello world".
• A view resolver that passes all returned view names to the above view.

To create the view: Extend: org.springframework.web.servlet.View Your implementation can then write "hello world" to the http response.

To create the view resolver: Extend: org.springframework.web.servlet.ViewResolver Your implementation should always te return your previously created view.

You can see that the viewresolver base class is where you have acceess to the returned view name. See: https://fisheye.springsource.org/browse/spring-framework/spring-webmvc/src/main/java/org/springframework/web/servlet/ViewResolver.java

This is the most basic way to answer your question. Spring offers many implementations of these classes for more specialised purposes that may suit your use case.

Hope this helps. Let me know if you need any more details.