Parameter


1   /*
2    * JOnAS: Java(TM) Open Application Server
3    * Copyright (C) 1999 Bull S.A.
4    * Contact: jonas-team@objectweb.org
5    * 
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2.1 of the License, or any later version.
10   * 
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   * 
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
19   * USA
20   *
21   * Initial developer(s): Nicolas Christin
22   * Contributor(s): ______________________________________.
23   *
24   * --------------------------------------------------------------------------
25   * $Id: Parameter.java,v 1.6 2003/11/21 01:13:08 skrupanszky Exp $
26   * --------------------------------------------------------------------------
27   */
28  
29  
30  package org.objectweb.jonas.newbean;
31  
32  
33  import java.io.BufferedReader  ;
34  import java.io.InputStreamReader  ;
35  import java.io.IOException  ;
36  
37  import org.apache.velocity.VelocityContext;
38  
39  
40  /**
41   * This class represents a parameter the user may be prompted for. It
42   * is responsible for asking the user for a value, validating his
43   * input, exporting relevant datas into Velocity's context, and
44   * deciding what should be the next parameter to ask.<p>
45   *
46   * A parameter is created by subclassing this class and overriding the
47   * following abstract methods:
48   *
49   * <ul>
50   *   <li>{@link #getPrompt()}</li>
51   *   <li>{@link #isValid()}</li>
52   *   <li>{@link #export()}</li>
53   *   <li>{@link #getNextParameter()}</li>
54   * </ul>
55   */
56  public abstract class Parameter {
57  
58      private static final String   PROMPT = "> ";
59      private static final int INPUT_BUFFER_SIZE = 80;
60      private static BufferedReader   reader =
61          new BufferedReader  (new InputStreamReader  (System.in));
62  
63      /** 
64       * The Velocity context into which this parameter's variables will
65       * be exported.
66       */
67      protected VelocityContext vContext = null;
68  
69      /**
70       * This parameter's value, as entered by the user.
71       */
72      protected String   value = null;
73  
74      
75      /**
76       * Creates a new parameter that will export its variables into the
77       * specified Velocity context.
78       *
79       * @param context the Velocity context into which variables will
80       * be exported
81       */
82      public Parameter(VelocityContext context) {
83          vContext = context;
84      }
85  
86  
87      /**
88       * Recusively walk through the parameters graph, obtaining
89       * parameter ({@link #obtainValue()}) values and exporting ({@link
90       * #export()}) them.<p>
91       *
92       * The path taken through the parameter graph may change depending
93       * on the values entered by the user. It is determined after each
94       * valid input by a call to {@link #getNextParameter()}.
95       */
96      public void walkThrough() {
97          obtainValue();
98          export();
99          Parameter nextParameter = getNextParameter();
100         if (nextParameter != null) {
101             nextParameter.walkThrough();
102         }
103     }
104 
105 
106     /**
107      * Obtains the value of this parameter. This method prompts the
108      * user for a value, stores it into {@link #value} through the
109      * {@link #isValid()}. This process is repeated until the value is
110      * valid.
111      */
112     public void obtainValue() {
113 
114         // check first if a cmd-line value has been specified
115         String    inp = getCmdArg( getArgKeyword() );
116         if( inp!=null ) {
117             setValue(inp);
118             if( isValid() ) { return; }
119         }
120 
121         for (;;) {
122             String   input = null;
123             System.out.println(getPrompt());
124             System.out.print("> ");
125             try {
126                 input = reader.readLine();
127             } catch (IOException   e) {
128                 NewBean.error(e.toString());
129             }
130             if (input == null) {
131                 input = "";
132             }
133             setValue(input);
134             if (isValid())
135                 break;
136             System.out.println("Invalid value, please retry");
137         }
138         System.out.println();
139     }
140 
141 
142     /**
143      * Sets the {@link #value} of this parameter. This method is
144      * called each time a value is entered is entered by the user,
145      * before its validity has been checked.<p>
146      *
147      * This implementation simply sets {@link #value} to
148      * <code>input</code>. You can override this method if you need to
149      * format this input, for example to convert it to uppercase.
150      */
151     public void setValue(String   input) {
152         value = input;
153     }
154 
155 
156     /**
157      * Returns the string used to prompt the user for a value.
158      * @return the string used to prompt the user for a value.
159      */
160     public abstract String   getPrompt();
161 
162 
163     /**
164      * Indicates whether this parameter as a valid value. This method
165      * can safely assume {@link #value} is not <code>null</code>.
166      *
167      * @return <code>true</code> if {@link #value} is valid,
168      * <code>false</code> otherwise
169      */
170     public abstract boolean isValid();
171 
172 
173     /**
174      * Exports the variables managed by this parameter into the
175      * associated Velocity context (<i>ie</i> {@link #vContext}).
176      */
177     public abstract void export();
178 
179 
180     /**
181      * Returns the parameter the user will be asked for after this
182      * one. This method is not invoked before a valid value has been
183      * entered for this parameter; therefor it is possible to decide
184      * which object to return based on the value of {@link #value}.<p>
185      *
186      * This method returns <code>null</code> if their is no more
187      * parameters.
188      *
189      * @return the next parameter the user should be prompted for
190      */
191     public abstract Parameter getNextParameter();
192 
193     /**
194      * @return the command line keyword string for this parameter
195      */
196     public abstract String        getArgKeyword();
197 
198     private String                getCmdArg( String   kwd )
199     {
200         return (String  )NewBean.commandLine.get( kwd );
201     }
202 
203 }
204
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