StateManager


1   package com.tonbeller.jpivot.tags;
2   
3   /**
4    * Manages state of JSPs.
5    * <p />
6    * Example: the user displays customerdetail.jsp for customer A, then productdetail.jsp for product B,
7    * and then again customerdetail.jsp for customer C. What should happen to A and B at this point?
8    * There are two possible strategies: stack and page.
9    * <p />
10   * PageStateStrategy preserves the latest state for every page. In the example A will be destroyed and 
11   * B and C will be preserved. So the user can display the productdetails.jsp with B and the 
12   * customerdetail.jsp with C using browser history buttons.
13   * <p />
14   * StackStateStrategy puts the pages into a stack. In the example, first customerdetail.jsp/A is pushed,
15   * then productdetail.jsp/B is pushed. In the last step, productdetail.jsp is popped because there is
16   * already a customerdetail.jsp on the stack. After productdetail.jsp is popped, the associated
17   * value of customerdetail.jsp is changed from A to C. The stack will only contain the value C for
18   * customerdetail.jsp, the values A and B will be destroyed.
19   *  
20   * @author av
21   * @since 15.02.2005
22   */
23  public interface StateManager {
24  
25    /**
26     * lifecycle: initialize() -> show() -> hide() -> ... -> show() -> hide() -> destroy()
27     * @author av
28     * @since 15.02.2005
29     */
30    public interface State {
31      /**
32       * the name of the state, for example the name of the JSP file. States that belong
33       * to the same name will replace each other, i.e. there will be only one state
34       * for each name.
35       */
36      String   getName();
37      /**
38       * called once before the state is used
39       */
40      void initialize() throws Exception  ;
41      /**
42       * called once after the state is no longer used
43       */
44      void destroy() throws Exception  ;
45      /**
46       * called when this state is made the visible one. There is only one visible state
47       */
48      void show() throws Exception  ;
49      /**
50       * called when the 
51       */
52      void hide() throws Exception  ;
53      
54    }
55    
56    /**
57     * makes s the current state. If there is already another state with the name of <code>s</code>,
58     * it will be destroyed and replaced by <code>s</code>. 
59     */
60    public void initializeAndShow(State s) throws Exception  ;
61    
62    /**
63     * makes a state with <code>name</code> the current state.
64     */
65    public void showByName(String   name) throws Exception  ;
66    
67    /**
68     * removes all states
69     */
70    public void destroyAll() throws Exception  ;
71  
72    /**
73     * removes + destroys a named state
74     */
75    public void destroyByName(String   name) throws Exception  ;
76    
77    /**
78     * logger for debug/test
79     */
80    void setLogger(StateLogger logger);
81    StateLogger getLogger();
82  }
83
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