Include tag, package tag, and Action Tag Name attribute in struts. xml

<Include/> label in struts. xml

When the system becomes largerStruts. xml

There is a lot of content, so we can useModular

Method

Distribute different configuration files in different configurations, and then load them in the same way by struts. xml.

For exampleStruts_1.xml

,Struts_2.xml

,Struts_3.xml

Three files are configured for different modules.

Finally, it can be integrated by struts. xml. The integration method is to include them.
<Include file = "struts_1.xml"/> <include file = "struts_2.xml"/> <include file = "struts_3.xml"/>

InStruts_1.xml

OrStruts_2.xml

AndStruts. xml

The configuration method in isExactly

Of

That is, they all haveRequired

XML Declaration

AndDTD

, And their DTD are the same. Next<Struts/> root element

That is, it cannot be consideredStruts_1.xml

If the file is contained, the XML declaration and DTD at the top are omitted. This is not acceptable.

Finally, Struts. XML is uniformly introduced, so the system loads the configurations such as struts_1.xml and struts_2.xml into the memory.

This is equivalent to modular configuration. For large and medium-sized systems, modular configuration is inevitable.

<Package name = "#"/> In struts. xml

In struts. XMLName

Can be named at will, without affecting anything else

Its name attribute only servesID <package/>

So that other <package/>Inheritance

It

<Package name = "struts-Default" abstract = "true">

AAbstract = "true"

Attribute

We found that this package declares the result type, interceptor, and so on, but it is not declared<Action/>

Configuration

HoweverStruts. xml

There are several <action/> configurations

ThereforeAbstract = "true"

Indicates that the current package is an abstract package, so it is not allowed to appear in the current package<Action/>

Configuration

Abstract packages are very similar to Java Abstract classes. It cannot be instantiated by itself. It can only be inherited, and several methods implemented by sub-classes are finally instantiated by sub-classes.

Therefore, the Struts-default package cannot contain any <action/> definition. The specific definition is defined by its Sub-package.

Meaning of extends in <package name = "struts2" extends = "struts-Default">

Available in struts2Package Mechanism

Differentiate different actionsSimilar functions

Put the action in onePackage

Medium

Similar to the Mechanism in Java,The difference is that the struts2 package supports multi-inheritance.

, As shown below
<Package name = "struts2" extends = "struts-default, jfreechart-Default">

In addition, it can be implemented between packages of struts2.Inheritance

Link

After inheritance, you can use everything in the inherited package.

So it is equivalent<Package name = "struts-Default"/>

All of these are inherited.

So you can directlyStruts-default.xml

All the result types and interceptors in the package are used by us.

If our package does not inherit the Struts-default package provided by struts2, a lot of work will become impossible.

When the struts2 application is startedAuto read struts-default.xml

To define everything in the file.Load to memory

Next, loadStruts. xml

File, and then read the information of the struts-default.xml in the memory

Then it will be added to our current application andDefault. Properties

Lines 180th and 181 have the following code:

### A list of configuration files automatically loaded by struts

Struts. configuration. Files = struts-default.xml, struts-plugin.xml, Struts. xml

Translation

: A list of configuration files automatically loaded by struts

The loading sequence of the application is as follows:Load struts-default.xml first

,Followed by struts-plugin.xml

,The most struts. xml

Therefore, the configuration information in the latter can overwrite the configuration information in the former.

<Package/> namespace attribute

If the namespace attribute of the <package/> label is not configuredNamespace = ""

Indicates that the current package is in the default namespace.

The namespace must startStart with a slash

Assume thatNamespace = "/hello"

And formAction = "login"

And then clickSubmit

Button

This will be displayed on the pageThe requested resource (/struts2/login) is not available

In this case, you can change the formAction = "/Hello/login"

Or use the namespace and Action attributes in the form to separate and write data.

That is<Form action = "login" namespace = "/Hello">

,Note that if login. Action is written, an error occurs.

After modifying the form action, it is displayed when you submit the form again.The requested resource (/struts2/Hello/login) is not available

This is because this path does not exist at all. The correct path should be/Struts2/Hello/login. Action

Therefore, After configuring the namespace of the package, you must manually add the action suffix, that isAction = "/Hello/login. Action"

If you submit it again, it will be displayed normally, and the browser will displayHttp: // 127.0.0.1: 8088/struts2/Hello/login. Action

In addition

: Assume thatAction = "/test/login. Action"

Request,Struts. xml

RootNo

The namespace isTest

Package

When struts2 finds that the namespace does not exist, it willDefault namespace

Search below<Action/>

Information

Assume that the message is sentAction = "/Hello/login. Action"

Request, when/Hello

If login. action does not exist in the namespace

Struts2 tries to go to the default namespace to find whether there is any <action/> information called login.

If no <action/> information with the name of login exists in the default namespace, an error cannot be found for the resource is reported.

Struts2 also supports the root namespace 【"/"]

When a direct requestContextpath

WhenRoot namespace

Search for matched actions

For example, requestHttp: // 127.0.0.1: 8088/project/BB. Action

Strtus2 will first"/"

Find the action in the namespace.
Server Root

YesHttp: // 127.0.0.1: 8088/

Root of the website

YesHttp: // 127.0.0.1: 8088/struts2_demo/

Hypothesis<A href = "/login. jsp"> </a>

, ThenActual point

YesHttp: // 127.0.0.1: 8088/login. jsp

That isRoot in JSP

Indicates thatServer Root

. WhileNamespace slash

RepresentativeWebsite Root

, Also calledProject Root

OrApplication Root

The name value of <action/> In struts. xml cannot start with a slash.

This is causedDefault. Properties

The attribute of row 109th is determined, that isStruts. Enable. slashesinactionnames

Default Value:False

For example, in struts. XML, the namespace attribute of <package/> is not specified and written<Action name = "Hello/login">

Then write in the formAction = "<% = request. getcontextpath () %>/Hello/login. Action"

And can still be accessed normally.

Note: You cannot write<Action name = "/Hello/login"/>

OtherwiseReport Error 404

In short, you can directly use the namespace. We do not recommend that you modify it.Struts. Enable. slashesinactionnames

Attribute, keep the default configuration.