Warning
This page is DEPRECATED, please refer to the new source http://struts.apache.org/plugins/convention/

Table of Contents

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Introduction

The Convention Plugin is bundled with Struts since 2.1 and replaces the Codebehind Plugin and Zero Config plugins. It provides the following features:

...

In order to use the Convention plugin, you first need to add the JAR file to the WEB-INF/lib directory of your application or include the dependency in your project's Maven POM file.

Code Block

	xml
	xml


<dependency>
    <groupId>org.apache.struts</groupId>
    <artifactId>struts2-convention-plugin</artifactId>
    <version>2<version>X.1X.6<X</version>
</dependency>

Where X.X.X is the current version of Struts 2. Please remember that the Convention Plugin is available from version 2.1.6.

Converting a Codebehind based application to Convention

...

If you are using REST with the Convention plugin, make sure you set these constants in struts.xml:

Code Block

	xml
	xml


<constant name="struts.convention.action.suffix" value="Controller"/>
<constant name="struts.convention.action.mapAllMatches" value="true"/>
<constant name="struts.convention.default.parent.package" value="rest-default"/>

...

Now that the Convention plugin has been added to your application, let's start with a very simple example. This example will use an actionless result that is identified by the URL. By default, the Convention plugin assumes that all of the results are stored in WEB-INF/content. This can be changed by setting the property struts.convention.result.path in the Struts properties file to the new location. Don't worry about trailing slashes, the Convention plugin handles this for you. Here is our hello world JSP:

Code Block

	html
	html


<html>
<body>
Hello world!
</body>
</html>

If you start Tomcat (or whichever J2EE container you are using) and type in http://localhost:8080/hello-world^{Image Removed} (assuming that your context path is "/", ie. starting application from Eclipse) into your browser you should get this result:

Code Block

borderStyle	solid
title	WEB-INF/content/hello-world.jsp
borderStyle	solid


Hello world!

This illustrates that the Convention plugin will find results even when no action exists and it is all based on the URL passed to Struts.

...

These packages are located by the Convention plugin using a search methodology. First the Convention plugin finds packages named struts, struts2, action or actions. Any packages that match those names are considered the root packages for the Convention plugin. Next, the plugin looks at all of the classes in those packages as well as sub-packages and determines if the classes implement com.opensymphony.xwork2.Action or if their name ends with Action (i.e. FooAction). Here's an example of a few classes that the Convention plugin will find:

Code Block

title	Classes


com.example.actions.MainAction
com.example.actions.products.Display (implements com.opensymphony.xwork2.Action)
com.example.struts.company.details.ShowCompanyDetailsAction

...

Code Block

title	Namespaces


com.example.actions.MainAction -> /
com.example.actions.products.Display -> /products
com.example.struts.company.details.ShowCompanyDetailsAction -> /company/details

Next, the plugin determines the URL of the resource using the class name. It first removes the word Action from the end of the class name and then converts camel case names to dashes. In our example the full URLs would be:

Code Block

title	Full URLs


com.example.actions.MainAction -> /main
com.example.actions.products.Display -> /products/display
com.example.struts.company.details.ShowCompanyDetailsAction -> /company/details/show-company-details

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 

public class HelloWorld extends ActionSupport {
  private String message;

  public String getMessage() {
    return message;
  }

  public String execute() {
    message = "Hello World!";
    return SUCCESS;
  }
}

If you compile this class and place it into your application in the WEB-INF/classes, the Convention plugin will find the class and map the URL /hello-world to it. Next, we need to update our JSP to print out the message we setup in the action class. Here is the new JSP:

Code Block

borderStyle

borderStyle	solid
title	WEB-INF/content/hello-world.jsp		solid


<html>
<body>
The message is ${message}
</body>
</html>

Note
Please notice that the expression `${message`} will work without adding JSP directive `isELIgnored="false"`.

If start up the application server and open up http://localhost:8080/hello-world^{Image Removed} in our browser, we should get this result:

Code Block

borderStyle	solid
title	Result	borderStyle	solid


The message is Hello World!

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 

public class HelloWorld extends ActionSupport {
  private String message;

  public String getMessage() {
    return message;
  }

  public String execute() {
    if (System.currentTimeMillis() % 2 == 0) {
      message = "It's 0";
      return "zero";
    }

    message = "It's 1";
    return SUCCESS;
  }
}

...

Code Block

title	WEB-INF/content/hello-world.jsp


<html>
<body>
The error message is ${message}
</body>
</html>

...

URL	Result	File that could match	Result Type
/hello	success	/WEB-INF/content/hello.jsp	Dispatcher
/hello	success	/WEB-INF/content/hello-success.htm	Dispatcher
/hello	success	/WEB-INF/content/hello.ftl	FreeMarker
/hello-world	input	/WEB-INF/content/hello-world-input.vm	Velocity
/test1/test2/hello	error	/WEB-INF/content/test/test2/hello-error.html	Dispatcher

Chaining

If one action returns the name of another action in the same package, they will be chained together, if the first action doesn't have any result defined for that code. In the following example:

Multiple names

It is possible to define multiple names for the same result:

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language	java

@Action(results =

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionSupport; 

public class HelloAction extends ActionSupport {
    @Action@Result(name={"fooerror")
    public String foo() {
        return "bar";
    }

    @Action("foo-bar"), "input"}, location="input-form.jsp"),
    public String bar() {
        return SUCCESS;
    }
}

The "foo" action will be executed, because no result is found, the Convention plugin tries to find an action named "foo-bar" on the same package where "foo" is defined. If such an action is found, it will be invoked using the "chain" result.

XWork packages

@Result(name="success", location="success.jsp")
})

Such functionality was added in Struts 2.5

Chaining

If one action returns the name of another action in the same package, they will be chained together, if the first action doesn't have any result defined for that code. In the following example:

Code Block

title	com.example.actions.HelloWorld

package com.example.actions;

import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionSupport;

public class HelloAction extends ActionSupport {
    @Action("foo")
    public String foo() {
        return "bar";
    }

    @Action("foo-bar")
    public String bar() {
        return SUCCESS;
    }
}

The "foo" action will be executed, because no result is found, the Convention plugin tries to find an action named "foo-bar" on the same package where "foo" is defined. If such an action is found, it will be invoked using the "chain" result.

XWork packages

Actions are Actions are placed on a custom XWork package which prevents conflicts. The name of this package is based on the Java package the action is defined in, the namespace part of the URL for the action and the parent XWork package for the action. The parent XWork package is determined based on the property named struts.convention.default.parent.package(defaults to convention-default), which is a custom XWork package that extends struts-default.

...

Code Block

title	XWork package naming


<java-package>#<namespace>#<parent-package>

Using our example from above, the XWork package for our action would be:

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borderStyle	solid
title	XWork package naming	borderStyle	solid


com.example.actions#/#conventionDefault

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;

public class HelloWorld extends ActionSupport {
  @Action("/different/url")
  public String execute() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;

public class HelloWorld extends ActionSupport {
  @Actions({
    @Action("/different/url"),
    @Action("/another/url")
  })
  public String execute() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;

public class HelloWorld extends ActionSupport {
  @Action("/different/url")
  public String execute() {
    return SUCCESS;


  }

  @Action("url")
  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;

public class HelloWorld extends ActionSupport {
  @Action(interceptorRefs={@InterceptorRef("validation"), @InterceptorRef("defaultStack")})
  public String execute() {
    return SUCCESS;
  }

  @Action("url")
  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;

public class HelloWorld extends ActionSupport {
  @Action(interceptorRefs=@InterceptorRef(value="validation",params={"programmatic", "false", "declarative", "true}))
  public String execute() {
    return SUCCESS;
  }

  @Action("url")
  public String doSomething() {
    return SUCCESS;
  }
}

If interceptors are not specified, the default stack is applied.

Info
You can specify className parameter which can be especially useful when Spring Framework is used to instantiate actions.

Applying @Action and @Actions at the class level

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;

@InterceptorRefs({
    @InterceptorRef("interceptor-1"),
    @InterceptorRef("defaultStack")
})
public class HelloWorld extends ActionSupport {
  @Action(value="action1", interceptorRefs=@InterceptorRef("validation"))
  public String execute() {
    return SUCCESS;
  }

  @Action(value="action2")
  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.Results;

@Results({
  @Result(name="failure", location="fail.jsp")
})
public class HelloWorld extends ActionSupport {
  @Action(value="/different/url", 
    results={@Result(name="success", location="http://struts.apache.org", type="redirect")}
  )
  public String execute() {
    return SUCCESS;
  }

  @Action("/another/url")

  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Actions;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.Results;

public class HelloWorld extends ActionSupport {
  @Action(value="/different/url", 
    results={@Result(name="success", type="httpheader", params={"status", "500", "errorMessage", "Internal Error"})}
  )
  public String execute() {
    return SUCCESS;
  }

  @Action("/another/url")
  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorl


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Namespace;

@Namespace("/custom")
public class HelloWorld extends ActionSupport {
  @Action("/different/url")
  public String execute() {
    return SUCCESS;
  }

  @Action("url")
  public String doSomething() {
    return SUCCESS;
  }
}

...

Code Block

title	com/example/actions/package-info.java


@org.apache.struts2.convention.annotation.Namespace("/custom")
package com.example.actions;

...

Code Block

title	com.example.actions.HelloWorl


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.ResultPath;

@ResultPath("/WEB-INF/jsps")
public class HelloWorld extends ActionSupport {
  public String execute() {
    return SUCCESS;
  }
}

...

Code Block

title	com.example.actions.HelloWorld


package com.example.actions;

import com.opensymphony.xwork2.ActionSupport; 
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.ParentPackage;

@ParentPackage("customXWorkPackage")
public class HelloWorld extends ActionSupport {
  public String execute() {
    return SUCCESS;
  }
}

...

Code Block

title	ExceptionsActionLevelAction.java


@ExceptionMappings({
    @ExceptionMapping(exception = "java.lang.NullPointerException", result = "success", params = {"param1", "val1"})
})
public class ExceptionsActionLevelAction {

    public String execute() throws Exception {
        return null;
    }
}

The parameters defined by params are passed to the result. Exception mappings can also be applied to the action level:

Code Block


public class ExceptionsMethodLevelAction {
    @Action(value = "exception1", exceptionMappings = {
            @ExceptionMapping(exception = "java.lang.NullPointerException", result = "success", params = {"param1", "val1"})
    })
    public String run1() throws Exception {
        return null;
    }
}

...

By default the Convention plugin will not scan jar files for actions. For a jar to be scanned, its URL needs to match at least one of the regular expressions in struts.convention.action.includeJars. In this example myjar1.jar and myjar2.jar will be scanned:

Code Block

	xml
	xml


<constant name="struts.convention.action.includeJars" value=".*?/myjar1.*?jar(!/)?,.*?/myjar2*?jar(!/)?"

Note that the regular expression will be evaluated against the URL of the jar, and not the file name, the jar URL can contain a path to the jar file and a trailing "!/".

Automatic configuration reloading

file and a trailing "!/".

Automatic configuration reloading

The Convention plugin can automatically reload configuration changes, made in classes the contain actions, without restarting the container. This is a similar behavior to the automatic xml configuration reloading. To enable this feature, add this to your struts.xml file:

Code Block

	xml
	xml

<constant name="struts.devMode" value="true"/>
<constant name="struts.convention.classes.reload" value="true" />

This feature is experimental and has not been tested on all container, and it is strongly advised not to use it in production environments.

JBoss

When using this plugin with JBoss, you need to set the following constantsThe Convention plugin can automatically reload configuration changes, made in classes the contain actions, without restarting the container. This is a similar behavior to the automatic xml configuration reloading. To enable this feature, add this to your struts.xml file:

Code Block

	xml
	xml


<constant name="struts.convention.devModeexclude.parentClassLoader" value="true" />
<constant name="struts.convention.classesaction.reloadfileProtocols" value="truejar,vfsfile,vfszip" />

This feature is experimental and has not been tested on all container, and it is strongly advised not to use it in production environments.

...

You can also check the JBoss 5 page for more details.

Jetty (embedded)

When using this plugin with JBossJetty in embedded mode, you need to set the following constants:

Code Block

	xml
	xml


<constant name="struts.convention.exclude.parentClassLoader" value="truefalse" />
<constant name="struts.convention.action.fileProtocols" value="jar,vfsfile,vfszipcode-source" />

Troubleshooting

Tips

Tip

title	Namespaces and Results

Make sure the namespace of the action is matched by one of the locators. The rest of the namespace after the locator, will be the namespace of the action, and will be used to find the results. For example, a class called "ViewAction" in the package "my.example.actions.orders" will be mapped to the URL /orders/view.action, and the results must be under /WEB-INF/content/orders, like /WEB-INF/content/orders/view-success.jsp.

Tip

title	Use the Configuration Browser Plugin

Add the Config Browser Plugin plugin to the lib folder or maven dependencies, and then visit: http://localhost:8080/CONTEXT/config-browser/index.action^{Image Removed}, to see the current action mappings.

...

The Convention plugin can be extended in the same fashion that Struts does. The following beans are defined by default:

Code Block

	xml
	xml


<bean type="org.apache.struts2.convention.ActionConfigBuilder" name="convention" class="org.apache.struts2.convention.PackageBasedActionConfigBuilder"/>
This interface defines how the action configurations for the current web application can be constructed. This must find all actions that are not specifically defined in the struts XML files or any plugins. Furthermore, it must make every effort to locate all action results as well.

<bean type="org.apache.struts2.convention.ActionNameBuilder" name="convention" class="org.apache.struts2.convention.SEOActionNameBuilder"/>
This interface defines the method that is used to create action names based on the name of a class.

<bean type="org.apache.struts2.convention.ResultMapBuilder" name="convention" class="org.apache.struts2.convention.DefaultResultMapBuilder"/>
This interface defines how results are constructed for an Action. The action information is supplied and the result is a mapping of ResultConfig instances to the result name.

<bean type="org.apache.struts2.convention.InterceptorMapBuilder" name="convention" class="org.apache.struts2.convention.DefaultInterceptorMapBuilder"/>
This interface defines how interceptors are built from annotations.

<bean type="org.apache.struts2.convention.ConventionsService" name="convention" class="org.apache.struts2.convention.ConventionsServiceImpl"/>
This interface defines the conventions that are used by the convention plugin. In most cases the methods on this class will provide the best default for any values and also handle locating overrides of the default via the annotations that are part of the plugin.

<constant name="struts.convention.actionConfigBuilder" value="convention"/>
<constant name="struts.convention.actionNameBuilder" value="convention"/>
<constant name="struts.convention.resultMapBuilder" value="convention"/>
<constant name="struts.convention.interceptorMapBuilder" value="convention"/>
<constant name="struts.convention.conventionsService" value="convention"/>

To plugin a different implementation for one of these classes, implement the interface, define a bean for it, and set the appropriate constant's value with the name of the new bean, for example:

Code Block

	xml
	xml


<bean type="org.apache.struts2.convention.ActionNameBuilder" name="MyActionNameBuilder" class="example.SultansOfSwingNameBuilder"/>
<constant name="struts.convention.actionNameBuilder" value="MyActionNameBuilder"/>

...

Add a constant element to your struts config file to change the value of a configuration setting, like:

Code Block

	xml
	xml


<constant name="struts.convention.result.path" value="/WEB-INF/mytemplates/"/>

Name	Default Value	Description
struts.convention.action.alwaysMapExecute	true	Set to false, to prevent Convention from creating a default mapping to "execute" when there are other methods annotated as actions in the class
struts.convention.action.includeJars		Comma separated list of regular expressions of jar URLs to be scanned. eg. ".*myJar-0\.2.,.thirdparty-0\.1.*"
struts.convention.action.packages		An optional list of action packages that this should create configuration for (they don't need to match a locator pattern)
struts.convention.result.path	/WEB-INF/content/	Directory where templates are located
struts.convention.result.flatLayout	true	If set to false, the result can be put in its own directory: resultsRoot/namespace/actionName/result.extension
struts.convention.action.suffix	Action	Suffix used to find actions based on class names
struts.convention.action.disableScanning	false	Scan packages for actions
struts.convention.action.mapAllMatches	false	Create action mappings, even if no @Action is found
struts.convention.action.checkImplementsAction	true	Check if an action implements com.opensymphony.xwork2.Action to create an action mapping
struts.convention.default.parent.package	convention-default	Default parent package for action mappins
struts.convention.action.name.lowercase	true	Convert action name to lowercase
struts.convention.action.name.separator	-	Separator used to build the action name, MyAction -> my-action. This character is also used as the separator between the action name and the result in templates, like action-result.jsp
struts.convention.package.locators	action,actions,struts,struts2	Packages whose name end with one of these strings will be scanned for actions
struts.convention.package.locators.disable	false	Disable the scanning of packages based on package locators
struts.convention.exclude.packages	org.apache.struts., org.apache.struts2., org.springframework.web.struts., org.springframework.web.struts2., org.hibernate.*	Packages excluded from the action scanning, packages already excluded cannot be included in other way, eg. org.demo.actions.exclude is specified as a part of the struts., org.apache.struts2., org.springframework.web.struts., org.springframework.web.struts2., org.hibernate.Packages excluded from the action scanning.convention.exclude.packages so all packages below are also excluded, eg. org.demo.actions.exclude.include even if include* is specified as a struts.convention.package.locators or struts.convention.action.packages
struts.convention.package.locators.basePackage		If set, only packages that start with its value will be scanned for actions
struts.convention.relative.result.types	dispatcher,velocity,freemarker	The list of result types that can have locations that are relative and the result location (which is the resultPath plus the namespace) prepended to them
struts.convention.redirect.to.slash	true	A boolean parameter that controls whether or not this will handle unknown actions in the same manner as Apache, Tomcat and other web servers. This handling will send back a redirect for URLs such as /foo to /foo/ if there doesn't exist an action that responds to /foo
struts.convention.classLoader.excludeParent	true	Exclude URLs found by the parent class loader from the list of URLs scanned to find actions (needs to be set to `false` for JBoss 5)
struts.convention.action.eagerLoading	false	If set, found action classes will be instantiated by the ObjectFactory to accelerate future use, setting it up can clash with Spring managed beans

Child pages

Versions Compared

Old Version 35

New Version Current

Key

Introduction

Converting a Codebehind based application to Convention

Chaining

Multiple names

XWork packages

Chaining

XWork packages

Applying @Action and @Actions at the class level

Automatic configuration reloading

Automatic configuration reloading

JBoss

Jetty (embedded)

Troubleshooting

Tips

Child pages

Page History

Versions Compared

Old Version 35

New Version Current

Key

Introduction

Converting a Codebehind based application to Convention

Chaining

Multiple names

XWork packages

Chaining

XWork packages

Applying @Action and @Actions at the class level

Automatic configuration reloading

Automatic configuration reloading

JBoss

Jetty (embedded)

Troubleshooting

Tips