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Simple Hibernate Tree Example

 
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Tree Example

This is the simplest way to illustrate a tree structure in Hibernate that I could cook up.

This example has only one persistent class: TreeNode. Notice that the annotations on TreeNode._children and TreeNode._parent show the semantics of the tree.

Then notice that this is an ordinary container/contained relationship. There really is nothing special about building a persistent tree.

This example relies on the semantics of eager loading. See my eager loading example and my lazy loading example.

This example also relies on the semantics of cascade saving. See my cascade save example.

Note: The original version of this post had a time-bomb in it. It would work as originally presented, but it could cause bizarre behavior if the pattern were used in a larger project. The original had an improper use of a java.util.List on line 11 of TreeNode.java (now it uses a java.util.Set). The issue is fully explained in my simple Hibernate list example.

Notice: This is provided with no warranty whatsoever. Use at your own risk.

This is the node class:

This is an example of how to use the persistent tree:
 
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