Index
Version 7 (Petr Mourek, 07/28/2010 02:40 pm)
| 1 | 2 | Roman Mackovčák | h1. Nested set plugin for Grails |
|---|---|---|---|
| 2 | 3 | Roman Mackovčák | |
| 3 | 3 | Roman Mackovčák | h2. What is Nested set? |
| 4 | 3 | Roman Mackovčák | |
| 5 | 3 | Roman Mackovčák | A nested set model is a way of organising hierarchical data in a relational database, "see Wikipedia":http://en.wikipedia.org/wiki/Nested_set_model. |
| 6 | 3 | Roman Mackovčák | |
| 7 | 3 | Roman Mackovčák | h2. Installation instructions |
| 8 | 3 | Roman Mackovčák | |
| 9 | 7 | Petr Mourek | Download the attachment:grails-nested-set-0.3.zip and run |
| 10 | 3 | Roman Mackovčák | |
| 11 | 3 | Roman Mackovčák | <pre><code class="java"> |
| 12 | 3 | Roman Mackovčák | grails install-plugin /path/to/the/plugin.zip |
| 13 | 3 | Roman Mackovčák | </code></pre> |
| 14 | 3 | Roman Mackovčák | |
| 15 | 3 | Roman Mackovčák | |
| 16 | 3 | Roman Mackovčák | h2. Essentials |
| 17 | 3 | Roman Mackovčák | |
| 18 | 3 | Roman Mackovčák | The NestedSet plugin injects the functionality of a nested set to any domain class. It is as simple as declaring a static variable. |
| 19 | 3 | Roman Mackovčák | |
| 20 | 3 | Roman Mackovčák | <pre><code class="java"> |
| 21 | 3 | Roman Mackovčák | class Employee { |
| 22 | 3 | Roman Mackovčák | String firstName |
| 23 | 3 | Roman Mackovčák | String lastName |
| 24 | 3 | Roman Mackovčák | |
| 25 | 3 | Roman Mackovčák | static nestedSet = true |
| 26 | 3 | Roman Mackovčák | } |
| 27 | 3 | Roman Mackovčák | </code></pre> |
| 28 | 3 | Roman Mackovčák | |
| 29 | 5 | Roman Mackovčák | Moreover, it does not interfere with the domain at all. The whole structure is stored in a domain class named NestedSet, in a separate table. |
| 30 | 3 | Roman Mackovčák | |
| 31 | 5 | Roman Mackovčák | It is possible to create a Nested set from any of your domain classes. Nevertheless, the tree structures can contain only classes with common ancestor. This ancestor have to be marked as a nested set. |
| 32 | 3 | Roman Mackovčák | |
| 33 | 3 | Roman Mackovčák | The following example will create 2 tree structures: Employee and Location. |
| 34 | 3 | Roman Mackovčák | |
| 35 | 3 | Roman Mackovčák | <pre><code class="java"> |
| 36 | 3 | Roman Mackovčák | class Employee { |
| 37 | 3 | Roman Mackovčák | String firstName |
| 38 | 3 | Roman Mackovčák | String lastName |
| 39 | 3 | Roman Mackovčák | |
| 40 | 3 | Roman Mackovčák | static nestedSet = true |
| 41 | 3 | Roman Mackovčák | } |
| 42 | 3 | Roman Mackovčák | |
| 43 | 3 | Roman Mackovčák | class Location{ |
| 44 | 3 | Roman Mackovčák | String name |
| 45 | 3 | Roman Mackovčák | static nestedSet = true |
| 46 | 3 | Roman Mackovčák | } |
| 47 | 3 | Roman Mackovčák | |
| 48 | 3 | Roman Mackovčák | class Continent extends Location{} |
| 49 | 3 | Roman Mackovčák | |
| 50 | 3 | Roman Mackovčák | class State extends Location{} |
| 51 | 3 | Roman Mackovčák | |
| 52 | 3 | Roman Mackovčák | class City extends Location{} |
| 53 | 3 | Roman Mackovčák | </code></pre> |
| 54 | 3 | Roman Mackovčák | |
| 55 | 3 | Roman Mackovčák | The Location tree structure can contain any of the descendants - Continent, State, City. |
| 56 | 3 | Roman Mackovčák | |
| 57 | 3 | Roman Mackovčák | The methods of the NestedSet are described in the following example. |
| 58 | 3 | Roman Mackovčák | |
| 59 | 3 | Roman Mackovčák | h2. Example |
| 60 | 3 | Roman Mackovčák | |
| 61 | 3 | Roman Mackovčák | <pre><code class="java"> |
| 62 | 3 | Roman Mackovčák | class Employee { |
| 63 | 3 | Roman Mackovčák | String firstName |
| 64 | 3 | Roman Mackovčák | String lastName |
| 65 | 3 | Roman Mackovčák | |
| 66 | 3 | Roman Mackovčák | static nestedSet = true |
| 67 | 3 | Roman Mackovčák | |
| 68 | 3 | Roman Mackovčák | /** |
| 69 | 3 | Roman Mackovčák | * Returns the direct manager of the employee |
| 70 | 3 | Roman Mackovčák | **/ |
| 71 | 3 | Roman Mackovčák | def manager() { |
| 72 | 3 | Roman Mackovčák | nestedSetGetParent() |
| 73 | 3 | Roman Mackovčák | } |
| 74 | 3 | Roman Mackovčák | |
| 75 | 3 | Roman Mackovčák | /** |
| 76 | 3 | Roman Mackovčák | * Returns all managers of the employee |
| 77 | 3 | Roman Mackovčák | **/ |
| 78 | 3 | Roman Mackovčák | def managers() { |
| 79 | 3 | Roman Mackovčák | nestedSetGetAncestors() |
| 80 | 3 | Roman Mackovčák | } |
| 81 | 3 | Roman Mackovčák | |
| 82 | 3 | Roman Mackovčák | /** |
| 83 | 3 | Roman Mackovčák | * Returns direct subordinates of the employee |
| 84 | 3 | Roman Mackovčák | **/ |
| 85 | 3 | Roman Mackovčák | def directSubordinates() { |
| 86 | 3 | Roman Mackovčák | nestedSetGetChildren() |
| 87 | 3 | Roman Mackovčák | } |
| 88 | 3 | Roman Mackovčák | |
| 89 | 3 | Roman Mackovčák | /** |
| 90 | 3 | Roman Mackovčák | * Returns direct subordinates of the employee and their subordinates |
| 91 | 3 | Roman Mackovčák | **/ |
| 92 | 3 | Roman Mackovčák | def allSubordinates() { |
| 93 | 3 | Roman Mackovčák | nestedSetGetDescendants() |
| 94 | 3 | Roman Mackovčák | } |
| 95 | 3 | Roman Mackovčák | |
| 96 | 3 | Roman Mackovčák | /** |
| 97 | 3 | Roman Mackovčák | * Returns the top managers (having no manager) |
| 98 | 3 | Roman Mackovčák | **/ |
| 99 | 3 | Roman Mackovčák | static def topManagers() { |
| 100 | 3 | Roman Mackovčák | nestedSetGetRoots() |
| 101 | 3 | Roman Mackovčák | } |
| 102 | 3 | Roman Mackovčák | |
| 103 | 3 | Roman Mackovčák | /** |
| 104 | 3 | Roman Mackovčák | * Promote employee to be the top manager |
| 105 | 3 | Roman Mackovčák | **/ |
| 106 | 3 | Roman Mackovčák | def makeTopManager() { |
| 107 | 3 | Roman Mackovčák | nestedSetMakeRoot() |
| 108 | 3 | Roman Mackovčák | } |
| 109 | 3 | Roman Mackovčák | |
| 110 | 3 | Roman Mackovčák | /** |
| 111 | 3 | Roman Mackovčák | * Remove the employee and all subordinates from hierarchy |
| 112 | 3 | Roman Mackovčák | **/ |
| 113 | 3 | Roman Mackovčák | def outsourceDepartment() { |
| 114 | 3 | Roman Mackovčák | nestedSetRemove() |
| 115 | 3 | Roman Mackovčák | } |
| 116 | 3 | Roman Mackovčák | |
| 117 | 3 | Roman Mackovčák | /** |
| 118 | 3 | Roman Mackovčák | * Adds a new subordinate |
| 119 | 3 | Roman Mackovčák | **/ |
| 120 | 3 | Roman Mackovčák | def addSubordinate(so) { |
| 121 | 3 | Roman Mackovčák | nestedSetAddChild(so) |
| 122 | 3 | Roman Mackovčák | } |
| 123 | 3 | Roman Mackovčák | |
| 124 | 3 | Roman Mackovčák | /** |
| 125 | 3 | Roman Mackovčák | * Move the whole department under different manager |
| 126 | 3 | Roman Mackovčák | **/ |
| 127 | 3 | Roman Mackovčák | def reorganize(newManager){ |
| 128 | 3 | Roman Mackovčák | nestedSetMoveTo(newManager) |
| 129 | 3 | Roman Mackovčák | } |
| 130 | 3 | Roman Mackovčák | |
| 131 | 3 | Roman Mackovčák | String toString() { |
| 132 | 3 | Roman Mackovčák | "$firstName $lastName" |
| 133 | 3 | Roman Mackovčák | } |
| 134 | 3 | Roman Mackovčák | } |
| 135 | 3 | Roman Mackovčák | } |
| 136 | 3 | Roman Mackovčák | </code></pre> |
| 137 | 3 | Roman Mackovčák | |
| 138 | 3 | Roman Mackovčák | h2. Limitations |
| 139 | 3 | Roman Mackovčák | |
| 140 | 3 | Roman Mackovčák | * If DB set to update, it does not create the appropriate indexes.... Human:Hibernate 0:1 |
| 141 | 3 | Roman Mackovčák | * It works well for "slowly changing" (static) hierarchical structures. The dynamic ones should be stored using different structure. |