java - 将数据库表转换为 JTree

Question

任何人都可以提供一个工作示例代码来将具有父子关系的 Oracle DB 表转换为 Java 代码中的 JTree 吗？

Table T (columns: Id, Parent_Id, Description).

我搜索了许多类似的问题，但对于 JTree 新手来说，所有问题似乎都模糊且不完整。我不需要任何代码来连接数据库，只需要检查结果并填充 JTree。

谢谢

Answer 1

当我开始使用 JTree 时，我实现了这个与您的问题非常相似的类。

检查方法：getElementTreeFromPlainList这或多或少是用于从持久层获取数据的方法和createTreeNodesForElement为树创建节点的方法。

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

public class MyJFrame extends JFrame {

    private static final long serialVersionUID = 1L;

    private static List<String[]> data = new ArrayList<String[]>();

    static {
        data.add(new String[] { "Id1", "Start 1", null });
        data.add(new String[] { "Id2", "Node 1.1", "Id3" });
        data.add(new String[] { "Id3", "Node 1", "Id1" });
        data.add(new String[] { "Id4", "Node 1.2", "Id3" });
        data.add(new String[] { "Id5", "Node 2", "Id1" });
        data.add(new String[] { "Id6", "Start 2", null });
    }

    public static void main(final String[] args) {
        new MyJFrame();
    }

    MyJFrame() {
        JTree tree = new JTree();

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Found Nodes");

        createTreeNodesForElement(root, getElementTreeFromPlainList());

        tree.setModel(new DefaultTreeModel(root));

        add(tree);

        setVisible(true);
        setBounds(0, 0, 200, 200);
    }

    Collection<Element> getElementTreeFromPlainList() {
        // builds a map of elements object returned from store
        Map<String, Element> values = new HashMap<String, Element>();
        for (String[] s : data) {
            values.put(s[0], new Element(s[2], s[1]));
        }

        // creates a result list
        Collection<Element> result = new ArrayList<MyJFrame.Element>();

        // for each element in the result list that has a parent, put it into it
        // otherwise it is added to the result list
        for (Element e : values.values()) {
            if (e.parent != null) {
                values.get(e.parent).getChildren().add(e);
            } else {
                result.add(e);
            }
        }

        return result;
    }

    void createTreeNodesForElement(final DefaultMutableTreeNode dmtn, final Collection<Element> elements) {
        // for each element a tree node is created
        for (Element child : elements) {
            DefaultMutableTreeNode created = new DefaultMutableTreeNode(child.getName());
            dmtn.add(created);
            createTreeNodesForElement(created, child.getChildren());
        }
    }

    public static class Element {
        private final String parent;
        private final String name;
        private final Collection<Element> children = new ArrayList<MyJFrame.Element>();

        public Element(final String parent, final String name) {
            super();
            this.parent = parent;
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public Collection<Element> getChildren() {
            return children;
        }

    }

}