新增 TreeBuilder 工具类。

src/main/java/xyz/zhouxy/plusone/commons/util/TreeBuilder.java

@@ -0,0 +1,39 @@
+package xyz.zhouxy.plusone.commons.util;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.BiConsumer;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class TreeBuilder<T, TIdentity> {
+    private final Collection<T> nodes;
+    private final Function<T, TIdentity> identityGetter;
+    private final Function<T, Optional<TIdentity>> parentIdentityGetter;
+    private final BiConsumer<T, T> addChildrenMethod;
+
+    public TreeBuilder(Collection<T> nodes, Function<T, TIdentity> identityGetter,
+            Function<T, Optional<TIdentity>> parentIdentityGetter, BiConsumer<T, T> addChildren) {
+        this.nodes = nodes;
+        this.identityGetter = identityGetter;
+        this.parentIdentityGetter = parentIdentityGetter;
+        this.addChildrenMethod = addChildren;
+    }
+
+    public List<T> buildTree() {
+        Map<TIdentity, T> identityNodeMap = MoreCollections.toHashMap(nodes, identityGetter);
+        List<T> result = this.nodes.stream()
+                .filter(node -> !this.parentIdentityGetter.apply(node).isPresent())
+                .collect(Collectors.toList());
+        for (T node : this.nodes) {
+            Optional<TIdentity> parentIdentity = parentIdentityGetter.apply(node);
+            if (parentIdentity.isPresent() && identityNodeMap.containsKey(parentIdentity.get())) {
+                T parentNode = identityNodeMap.get(parentIdentity.get());
+                addChildrenMethod.accept(parentNode, node);
+            }
+        }
+        return result;
+    }
+}

src/test/java/xyz/zhouxy/plusone/commons/util/TreeBuilderTests.java

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+package xyz.zhouxy.plusone.commons.util;
+
+import java.util.List;
+import java.util.Optional;
+
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.collect.Lists;
+
+import lombok.ToString;
+
+class TreeBuilderTests {
+
+    private static final Logger log = LoggerFactory.getLogger(TreeBuilderTests.class);
+
+    @Test
+    void testBuildTree() {
+        List<Menu> menus = Lists.newArrayList(
+            MenuItem.of("A", "首页", "/home"),
+            MenuList.of("B", "系统管理"),
+                MenuItem.of("B", "B001", "功能管理", "/sys/function-mgmt"),
+                MenuItem.of("B", "B002", "角色管理", "/sys/role-mgmt"),
+                MenuItem.of("B", "B003", "账号管理", "/sys/account-mgmt"),
+                MenuItem.of("B", "B004", "系统参数管理", "/sys/param-mgmt"),
+            MenuList.of("C", "一级菜单C"),
+                MenuList.of("C", "C1", "二级菜单C1"),
+                    MenuItem.of("C1", "C1001", "三级菜单C1001", "/c/c1/c1001"),
+                    MenuItem.of("C1", "C1002", "三级菜单C1002", "/c/c1/c1002"),
+                MenuItem.of("C", "C2", "二级菜单C2", "/c/c2"),
+                MenuItem.of("C", "C3", "二级菜单C3", "/c/c3")
+        );
+        List<Menu> menuTree = new TreeBuilder<Menu, String>(
+                menus,
+                Menu::getMenuCode,
+                Menu::getParentMenuCode,
+                Menu::addChild)
+                .buildTree();
+        log.info("menuTree: {}", menuTree);
+    }
+}
+
+@ToString
+abstract class Menu {
+    protected final String parentMenuCode;
+    protected final String menuCode;
+    protected final String title;
+
+    public Menu(String parentMenuCode, String menuCode, String title) {
+        this.parentMenuCode = parentMenuCode;
+        this.menuCode = menuCode;
+        this.title = title;
+    }
+
+    public String getMenuCode() {
+        return menuCode;
+    }
+
+    public Optional<String> getParentMenuCode() {
+        return Optional.ofNullable(parentMenuCode);
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public abstract void addChild(Menu child);
+}
+
+@ToString(callSuper = true)
+class MenuItem extends Menu {
+
+    private final String url;
+
+    private MenuItem(String parentMenuCode, String menuCode, String title, String url) {
+        super(parentMenuCode, menuCode, title);
+        this.url = url;
+    }
+
+    static MenuItem of(String parentMenuCode, String menuCode, String title, String url) {
+        return new MenuItem(parentMenuCode, menuCode, title, url);
+    }
+
+    static MenuItem of(String menuCode, String title, String url) {
+        return new MenuItem(null, menuCode, title, url);
+    }
+
+    public String getUrl() {
+        return url;
+    }
+
+    @Override
+    @Deprecated
+    public void addChild(Menu child) {
+        throw new UnsupportedOperationException("Unimplemented method 'addChild'");
+    }
+}
+
+@ToString(callSuper = true)
+class MenuList extends Menu {
+
+    private List<Menu> children;
+
+    private MenuList(String parentMenuCode, String menuCode, String title) {
+        super(parentMenuCode, menuCode, title);
+    }
+
+    static MenuList of(String parentMenuCode, String menuCode, String title) {
+        return new MenuList(parentMenuCode, menuCode, title);
+    }
+
+    static MenuList of(String menuCode, String title) {
+        return new MenuList(null, menuCode, title);
+    }
+
+    static MenuList of(String menuCode, String title, Iterable<Menu> children) {
+        return of(null, menuCode, title, children);
+    }
+
+    static MenuList of(String parentMenuCode, String menuCode, String title, Iterable<Menu> children) {
+        MenuList instance = of(parentMenuCode, menuCode, title);
+        for (Menu child : children) {
+            instance.addChild(child);
+        }
+        return instance;
+    }
+
+    @Override
+    public void addChild(Menu child) {
+        if (this.children == null) {
+            this.children = Lists.newArrayList();
+        }
+        this.children.add(child);
+    }
+}