Saving Data
There are times when you wish to save data. The XWiki platform offers various places that you can use depending on your needs. Here's a rundown of all the options you have.
Transient Saves
Execution Context
If the data to be saved should only be saved for the duration of a request (i.e. a call to an XWiki URL) then you should declare a property in the Execution Context.
For example, from Java in a Component:
@Inject Execution execution;
...
// Declaring
ExecutionContext ec = execution.getContext();
ec.newProperty("mykey").initial(initialValue).declare();
...
// Updating
ec.setProperty("mykey", newValue);
...
// Retrieving
Object myvalue = e.getProperty("mykey");
Execution Context Property Declaration
The declaration is currently optional, the property will be implicitly declared when set the first time. The declaration can be made in an ExecutionContextInitializer component. The initialize method of all such components that are available in the classpath and have been specified in a components.txt file will be called when the execution context is first initialized during the request.
import org.xwiki.context.ExecutionContextInitializer;
import org.xwiki.context.ExecutionContextException;
import org.xwiki.component.annotation.Component;
@Component
public class DeclareMyPropertyExecutionContextInitializer implements ExecutionContextInitializer
{
@Override
public void initialize(ExecutionContext executionContext)
{
if (!executionContext.hasProperty("mykey")) {
executionContext.newProperty("mykey").type(String.class).nonNull().initial("").declare();
}
}
}
In the above example you can see that it is possible to set various attributes on the property when it is beeing declared. The attributes currently supported are listed in the table below.
During a request cycle, some components may activate a clean or a cloned execution context by pushing to the execution context stack. You can control how you want your property to be managed in these situations by setting attributes.
| Attribute | Parameters | Description |
|---|---|---|
| cloneValue() | - | Indicate that you want the value to be cloned when the execution context is cloned or when your property is inherited from a parent execution context |
| makeFinal() | - | Indicate that an exception should be thrown if someone tries to replace the initial value object |
| inherited() | - | Indicate that the property should be inherited by any new execution context that is pushed within the current request |
| nonNull() | - | Indicate that an exception should be thrown if null is set as the property value |
| type(Class<?> type) |
| Set a type for performing typechecking when updating the value object. |
Wiki Page Access to Execution Context
From a wiki page:
import org.xwiki.context.*
def ec = services.component.getInstance(Execution.class).getContext()
ec.setProperty("mykey", myvalue)
{{/groovy}}
For example:
$xcontext.put("mykey", value)
{{/velocity}}
For example from Velocity in a wiki page:
$request.setAttribute("mykey", value)
{{/velocity}}
Servlet Session
If the data should last a little longer (i.e. for example span more than 1 request), you could save it in the Servlet Session (note that in this case your code will only work in a Servlet Environment).
For example, from Java in a Component:
@Inject Container container;
...
Request request = container.getRequest();
// Note that this is a bit of a hack and the notion of Session exists in the Container class (getSession()) but the Session interface is empty at the moment, making it useless)
if (request instanceof ServletRequest) {
HttpServletRequest servletRequest = (ServletRequest) request;
HttpSession session = servletRequest.getSession();
session.setAttribute("mykey", myvalue);
}
Example from a wiki page:
$request.getSession().setAttribute("mykey", myvalue)
{{/velocity}}
Temporary Directory
If the data should last even a little longer than a session, you could save it in a file in the environment's temporary directory.
For example, from Java in a Component:
import org.apache.commons.io.*;
@Inject Environment environment;
...
File tmpDir = environment.getTemporaryDirectory();
FileUtils.write(tmpDir, "something");
Servlet Context
If the Data should last as long as the web application is up, you could use the Servlet Context. It's not very easy to access it but it's possible (note that in this case your code will only work in a Servlet Environment).
For example, from Java in a Component:
import com.xpn.xwiki.*;
import com.xpn.xwiki.web.*;
@Inject Execution execution;
...
// Get the older XWiki Context
XWikiContext xc = (XWikiContext) execution.getContext().getProperty("xwikicontext");
XWikiEngineContext ec = xc.getEngineContext();
ec.setAttribute("mykey", myvalue);
Using the Cache API
You can also create a Cache and store data in it. See the Cache API.
Permanent Saves
Wiki Model
The best place to save data is usually in the wiki itself (See the Data Model and the API Guide for some examples). There are several places where you can store data in the model:
- In the document content itself
- In an XObject attached to a document
- In an attachment
Permanent Directory
Another possibility is to use the environment's permanent directory.
For example, from Java in a Component:
import org.apache.commons.io.*;
@Inject Environment environment;
...
File permDir = environment.getPermanentDirectory();
FileUtils.write(permDir, "something");
