TemplateContext


1   /*******************************************************************************
2    * Copyright (c) 2000, 2005 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.jface.text.templates;
12  
13  import java.util.HashMap  ;
14  import java.util.Map  ;
15  
16  import org.eclipse.jface.text.BadLocationException;
17  
18  /**
19   * Provides the context for a <code>Template</code> being resolved. Keeps track
20   * of resolved variables.
21   * <p>
22   * Clients may extend this class.
23   * </p>
24   *
25   * @since 3.0
26   */
27  public abstract class TemplateContext {
28  
29      /** The context type of this context */
30      private final TemplateContextType fContextType;
31      /** Additional variables. */
32      private final Map   fVariables= new HashMap  ();
33      /** A flag to indicate that the context should not be modified. */
34      private boolean fReadOnly;
35  
36      /**
37       * Creates a template context of a particular context type.
38       *
39       * @param contextType the context type of this context
40       */
41      protected TemplateContext(TemplateContextType contextType) {
42          fContextType= contextType;
43          fReadOnly= true;
44      }
45  
46      /**
47       * Returns the context type of this context.
48       *
49       * @return the context type of this context
50       */
51      public TemplateContextType getContextType() {
52          return fContextType;
53      }
54  
55      /**
56       * Sets or clears the read-only flag.
57       *
58       * @param readOnly the new read-only state
59       */
60      public void setReadOnly(boolean readOnly) {
61          fReadOnly= readOnly;
62      }
63  
64      /**
65       * Returns <code>true</code> if the receiver is read-only, <code>false</code> otherwise.
66       *
67       * @return <code>true</code> if the receiver is read-only, <code>false</code> otherwise
68       */
69      public boolean isReadOnly() {
70          return fReadOnly;
71      }
72  
73      /**
74       * Defines the value of a variable.
75       *
76       * @param name the name of the variable
77       * @param value the value of the variable, <code>null</code> to un-define a variable
78       */
79      public void setVariable(String   name, String   value) {
80          fVariables.put(name, value);
81      }
82  
83      /**
84       * Returns the value of a defined variable.
85       *
86       * @param name the name of the variable
87       * @return returns the value of the variable, <code>null</code> if the variable was not defined
88       */
89      public String   getVariable(String   name) {
90          return (String  ) fVariables.get(name);
91      }
92  
93      /**
94       * Evaluates the template in this context and returns a template buffer.
95       * <p>
96       * Evaluation means translating the template into a <code>TemplateBuffer</code>,
97       * resolving the defined variables in this context and possibly formatting
98       * the resolved buffer.</p>
99       *
100      * @param template the template to evaluate
101      * @return returns the buffer with the evaluated template or <code>null</code> if the buffer could not be created
102      * @throws BadLocationException if evaluation fails due to concurrently changed documents etc.
103      * @throws TemplateException if the template specification is not valid
104      */
105     public abstract TemplateBuffer evaluate(Template template) throws BadLocationException, TemplateException;
106 
107     /**
108      * Tests if the specified template can be evaluated in this context.
109      * <p>Examples are templates defined for a different context (e.g. a javadoc
110      * template cannot be evaluated in Java context).</p>
111      *
112      * @param template the <code>Template</code> to check
113      * @return <code>true</code> if <code>template</code> can be evaluated
114      *         in this context, <code>false</code> otherwise
115      */
116     public abstract boolean canEvaluate(Template template);
117 
118 }
119
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