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1 {{box cssClass="floatinginfobox" title="**Contents**"}}
2 {{toc/}}
3 {{/box}}
4
5 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.
6
7 = Transient Saves =
8
9 == Execution Context ==
10
11 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**.
12
13 For example, from Java in a Component:
14
15 {{code language="java"}}
16 import org.xwiki.execution.*;
17
18 @Inject Execution execution;
19 ...
20 // Declaring
21 ExecutionContext ec = execution.getContext();
22 ec.newProperty("mykey").initial(initialValue).declare();
23 ...
24 // Updating
25 ec.setProperty("mykey", newValue);
26 ...
27 // Retrieving
28 Object myvalue = e.getProperty("mykey");
29 {{/code}}
30
31 === Execution Context Property Declaration ===
32
33 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.
34
35 {{code language="java"}}
36 import org.xwiki.context.ExecutionContext;
37 import org.xwiki.context.ExecutionContextInitializer;
38 import org.xwiki.context.ExecutionContextException;
39 import org.xwiki.component.annotation.Component;
40
41 @Component
42 public class DeclareMyPropertyExecutionContextInitializer implements ExecutionContextInitializer
43 {
44 @Override
45 public void initialize(ExecutionContext executionContext)
46 {
47 if (!executionContext.hasProperty("mykey")) {
48 executionContext.newProperty("mykey").type(String.class).nonNull().initial("").declare();
49 }
50 }
51 }
52 {{/code}}
53
54 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.
55
56 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.
57
58 |=(% style="width:25%" %)Attribute |=Parameters |=Description
59 |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
60 |makeFinal()| - |Indicate that an exception should be thrown if someone tries to replace the initial value object
61 |inherited()| - |Indicate that the property should be inherited by any new execution context that is pushed within the current request
62 |nonNull()| - |Indicate that an exception should be thrown if ##null## is set as the property value
63 |type(Class<?> type)|(((
64 ; type
65 : the class that the value object should be typechecked against
66 )))|Set a type for performing typechecking when updating the value object.
67
68 === Wiki Page Access to Execution Context ===
69
70 {{info}}
71 We currently [[cannot access easily the Execution Context from a wiki page>>https://jira.xwiki.org/browse/XCOMMONS-242]] but this should be improved. Currently it's not available from Velocity, but it is from Groovy.
72 {{/info}}
73
74 From a wiki page:
75
76 {{code}}
77 {{groovy}}
78 import org.xwiki.context.*
79
80 def ec = services.component.getInstance(Execution.class).getContext()
81 ec.setProperty("mykey", myvalue)
82 {{/groovy}}
83 {{/code}}
84
85 {{info}}
86 From a wiki page it's much easier to use the older **XWiki Context** (which is supposed to be fully replaced by the Execution Context at some point in the future).
87 {{/info}}
88
89 For example:
90
91 {{code}}
92 {{velocity}}
93 $xcontext.put("mykey", value)
94 {{/velocity}}
95 {{/code}}
96
97 {{warning}}
98 This requires Programming Rights.
99 {{/warning}}
100
101 {{info}}
102 It's also possible to save data in the HTTP Request even though it's recommended to use the Execution Context instead (since the Execution Context is independent of the execution environment and will work everywhere: Servlets, Portlets, JavaSE, etc).
103 {{/info}}
104
105 For example from Velocity in a wiki page:
106
107 {{code}}
108 {{velocity}}
109 $request.setAttribute("mykey", value)
110 {{/velocity}}
111 {{/code}}
112
113 == Servlet Session ==
114
115 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).
116
117 For example, from Java in a Component:
118
119 {{code language="java"}}
120 import org.xwiki.container.*;
121
122 @Inject Container container;
123 ...
124 Request request = container.getRequest();
125 // 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)
126 if (request instanceof ServletRequest) {
127 HttpServletRequest servletRequest = (ServletRequest) request;
128 HttpSession session = servletRequest.getSession();
129 session.setAttribute("mykey", myvalue);
130 }
131 {{/code}}
132
133 Example from a wiki page:
134
135 {{code}}
136 {{velocity}}
137 $request.getSession().setAttribute("mykey", myvalue)
138 {{/velocity}}
139 {{/code}}
140
141 == Temporary Directory ==
142
143 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.
144
145 For example, from Java in a Component:
146
147 {{code language="java"}}
148 import org.xwiki.environment.*;
149 import org.apache.commons.io.*;
150
151 @Inject Environment environment;
152 ...
153 File tmpDir = environment.getTemporaryDirectory();
154 FileUtils.write(tmpDir, "something");
155 {{/code}}
156
157 == Servlet Context ==
158
159 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).
160
161 For example, from Java in a Component:
162
163 {{code language="java"}}
164 import org.xwiki.container.*;
165 import com.xpn.xwiki.*;
166 import com.xpn.xwiki.web.*;
167
168 @Inject Execution execution;
169 ...
170 // Get the older XWiki Context
171 XWikiContext xc = (XWikiContext) execution.getContext().getProperty("xwikicontext");
172 XWikiEngineContext ec = xc.getEngineContext();
173 ec.setAttribute("mykey", myvalue);
174 {{/code}}
175
176 = Permanent Saves =
177
178 == Wiki Model ==
179
180 The best place to save data is usually in the wiki itself (See the [[Data Model>>platform:DevGuide.DataModel]] and the [[API Guide>>platform:DevGuide.APIGuide]] for some examples). There are several places where you can store data in the model:
181
182 * In the document content itself
183 * In an XObject attached to a document
184 * In an attachment
185
186 == Permanent Directory ==
187
188 Another possibility is to use the environment's permanent directory.
189
190 For example, from Java in a Component:
191
192 {{code language="java"}}
193 import org.xwiki.environment.*;
194 import org.apache.commons.io.*;
195
196 @Inject Environment environment;
197 ...
198 File permDir = environment.getPermanentDirectory();
199 FileUtils.write(permDir, "something");
200 {{/code}}

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