构建树形结构集合的方法-Java

完整代码如下

构建树形结构方法

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class TableUtils<T> {

    /**
     * 集合构建成层级结构
     *
     * ps：处于顶级的数据，上下级字段值必须为空
     *
     * @param list 集合
     * @param primaryKeyName 主键字段名称
     * @param nodeName 上下级字段名称
     * @param childName 存放子集合的字段名称
     * @param splitter 分割符
     * @return 层级结构的集合
     */
    public static <T> List<T> tree(List<T> list, String primaryKeyName, String nodeName, String childName, String splitter) {
        List<T> topNode = new ArrayList<>();
        try {
            LinkedList<T> linkedList = new LinkedList<>(list);
            while (!linkedList.isEmpty()) {
                T first = linkedList.removeFirst();
                Object nodeObj = getDeclaredFieldValue(first, nodeName);
                Object primaryKeyObj = getDeclaredFieldValue(first, primaryKeyName);
                Field childFiled = getDeclaredField(first, childName);
                if (JudgeUtils.isNull(childFiled.get(first))) {
                    childFiled.set(first, new ArrayList<>());
                }
                List<T> childList = (List<T>) childFiled.get(first);
                String nodeValue = "";
                if (JudgeUtils.isNull(nodeObj)) {
                    nodeValue += primaryKeyObj;
                } else {
                    String nodeCon = (String) nodeObj;
                    String node = nodeCon.endsWith(",") ? nodeCon.substring(0, nodeCon.lastIndexOf(",")) : nodeCon;
                    nodeValue = node + splitter + primaryKeyObj;
                }
                for (T node : linkedList) {
                    Object secondNodeObj = getDeclaredFieldValue(node, nodeName);
                    String secondNodeCon = JudgeUtils.isNull(secondNodeObj) ? "" : (String) secondNodeObj;
                    String secondNode = secondNodeCon.endsWith(",") ? secondNodeCon.substring(0, secondNodeCon.lastIndexOf(",")) : secondNodeCon;
                    if (nodeValue.equals(secondNode)) {
                        childList.add(node);
                    }
                }
            }
            for (T original : list) {
                if (JudgeUtils.isNull(getDeclaredFieldValue(original, nodeName))) {
                    topNode.add(original);
                }
            }
        } catch (IllegalAccessException | NoSuchFieldException e) {
            e.printStackTrace();
        }
        return topNode;
    }

    private static <T> Field getDeclaredField(T clz, String fieldName) throws NoSuchFieldException {
        Field field = clz.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        return field;
    }

    private static <T> Object getDeclaredFieldValue(T clz, String fieldName) throws NoSuchFieldException, IllegalAccessException {
        return getDeclaredField(clz, fieldName).get(clz);
    }

}

用到的校验方法

import java.lang.reflect.Field;

/**
 * 检验工具类
 */
public class JudgeUtils<T> {

    /**
     * 判断字符串为空
     *
     * @param str 字符串
     */
    public static boolean isEmpty(String str) {
        return str == null || "".equals(str.trim());
    }

    /**
     * 判断对象为空
     *
     * @param o 对象
     */
    public static boolean isNull(Object o) {
        return o == null;
    }

    /**
     * 判断对象及其字段全为空
     *
     * @param o 对象
     */
    public static boolean isAllNull(Object o) {
        boolean flag = isNull(o);
        if (!flag) {
            try {
                for (Field field : o.getClass().getDeclaredFields()) {
                    field.setAccessible(true);
                    if (!isNull(field.get(o))) {
                        return false;
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return flag;
    }

    /**
     * 断言-true则报错
     *
     * @param state 状态
     * @param msg 报错内容
     */
    public static void assertion(boolean state, String msg) {
        if (state) {
            throw new RuntimeException(msg);
        }
    }

    /**
     * 断言-检查对象不为空-true则报错-false则返回该对象
     *
     * @param t 对象
     * @param msg 报错内容
     */
    public static<T> T checkNotNull(T t, String msg) {
        if (t instanceof String) {
            assertion(isEmpty((String) t), msg);
        } else {
            assertion(isNull(t), msg);
        }
        return t;
    }

    /**
     * 断言-检查对象为空-true则返回该对象-false则报错
     *
     * @param t 对象
     * @param msg 报错内容
     */
    public static<T> T checkIsNull(T t, String msg) {
        if (t instanceof String) {
            assertion(!isEmpty((String) t), msg);
        } else {
            assertion(!isNull(t), msg);
        }
        return t;
    }

}

测试用例

测试表对象

import java.util.ArrayList;
import java.util.List;

public class TableTest {

    /**
     * 主键字段
     */
    private Long id;

    /**
     * 上下级字段(示例：1,3,5)
     * ps：顶级该值要为空
     */
    private String node;

    /**
     * 子集合字段
     */
    private List<TableTest> list = new ArrayList<>();

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getNode() {
        return node;
    }

    public void setNode(String node) {
        this.node = node;
    }

    public List<TableTest> getList() {
        return list;
    }

    public void setList(List<TableTest> list) {
        this.list = list;
    }

    public TableTest() {
    }

    public TableTest(Long id, String node, List<TableTest> list) {
        this.id = id;
        this.node = node;
        this.list = list;
    }

    @Override
    public String toString() {
        return "TableTest{" +
                "id=" + id +
                ", node='" + node + '\'' +
                ", list=" + list +
                '}';
    }
}

测试方法

import cn.cgj.system.domain.TableTest;
import cn.cgj.util.TableUtils;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.ArrayList;
import java.util.List;

@SpringBootTest
public class UnitTest {

    @Test
    public void test() throws NoSuchFieldException, IllegalAccessException {
        TableTest tableTop1 = new TableTest(1L, null, null);
        TableTest tableTop2 = new TableTest(2L, null, null);
        TableTest tableSon1 = new TableTest(3L, "1", null);
        TableTest tableSon2 = new TableTest(4L, "2,", null);
        TableTest tableSon3 = new TableTest(5L, "1,3", null);
        TableTest tableSon4 = new TableTest(6L, "2,4,", null);

        List<TableTest> list = new ArrayList<TableTest>() {{
            add(tableTop1);
            add(tableTop2);
            add(tableSon1);
            add(tableSon2);
            add(tableSon3);
            add(tableSon4);
        }};

        List<TableTest> hierarchy = TableUtils.tree(list, "id", "node", "list", ",");
        hierarchy.forEach(System.err::print);
    }
}