前言：如何通過遞歸去查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)，相信大家在平常肯定會(huì)遇到這樣的需求，這一章我們就好好研究下如何用遞歸去找。

目錄

一、遞歸找父節(jié)點(diǎn)或子節(jié)點(diǎn)

二、創(chuàng)建一張表關(guān)系表保存上面的關(guān)系

三、遞歸查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)核心代碼

四、演示查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)

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一、遞歸找父節(jié)點(diǎn)或子節(jié)點(diǎn)

1、根據(jù)下圖我如何去找下圖inst的父節(jié)點(diǎn)：inst->crlim->cust->custTotal

2、根據(jù)下圖我如何去找下圖cust的子節(jié)點(diǎn)：cust->crlim->inst、cash、instCash

?二、創(chuàng)建一張表關(guān)系表保存上面的關(guān)系

帶著上面的疑問，我們首先先創(chuàng)建一張關(guān)系表，把這些關(guān)系都存到表中。

CREATE TABLE `limit_mesh` (`id` int NOT NULL AUTO_INCREMENT,`parent_node` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL,`child_node` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL,PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (1, 'crilm', 'inst'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (2, 'crilm', 'cash'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (3, 'crilm', 'instCash'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (4, 'cust', 'crilm'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (5, 'custTotal', 'cust'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (6, 'cust', 'splmt'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (7, 'splmt', 'byj'); INSERT INTO `limit_mesh`(`id`, `parent_node`, `child_node`) VALUES (8, 'splmt', 'ygj');

三、遞歸查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)核心代碼

其他代碼這里就不詳細(xì)來寫了，只寫我們遞歸的核心代碼。

• 遞歸查詢父節(jié)點(diǎn)核心代碼

/*** 遞歸找父節(jié)點(diǎn)* @param nodeNo* @return*/public List<String> getLimitMeshParentList(String nodeNo) {List<String> parentList = new ArrayList<>();List<LimitMesh> limitMeshList = limitMeshService.getLimitMeshList();getParentNodeNo(limitMeshList,nodeNo,parentList);return parentList;}private List<String> getParentNodeNo(List<LimitMesh> limitMeshList,String nodeNo,List<String> parentList) {if (!parentList.contains(nodeNo)) {parentList.add(nodeNo);}List<String> parentRecursionList = getParentRecursionList(nodeNo,limitMeshList);if (CollectionUtils.isNotEmpty(parentRecursionList)) {if (!parentList.containsAll(parentRecursionList)) {parentList.addAll(parentRecursionList);}for (String str:parentRecursionList) {List<String> parentNodeNoList = getParentNodeNo(limitMeshList, str, parentList);if (!parentList.containsAll(parentNodeNoList)) {parentList.addAll(parentNodeNoList);}}}return parentList;}private List<String> getParentRecursionList(String nodeNo, List<LimitMesh> limitMeshList) {return limitMeshList.stream().filter(limitMesh -> limitMesh.getChildNode().equals(nodeNo)).map(limitMesh -> limitMesh.getParentNode()).collect(Collectors.toList());}

• 遞歸查詢子節(jié)點(diǎn)核心代碼

/*** 遞歸找子節(jié)點(diǎn)* @param nodeNo* @return*/public List<String> getLimitMeshChildList(String nodeNo) {List<String> childList = new ArrayList<>();List<LimitMesh> limitMeshList = limitMeshService.getLimitMeshList();getChildNodeNo(limitMeshList,nodeNo,childList);return childList;}private List<String> getChildNodeNo(List<LimitMesh> limitMeshList, String nodeNo, List<String> childList) {if (!childList.contains(nodeNo)) {childList.add(nodeNo);}List<String> childRecursionList = getChildRecursionList(nodeNo,limitMeshList);if (CollectionUtils.isNotEmpty(childRecursionList)) {if (!childList.containsAll(childRecursionList)) {childList.addAll(childRecursionList);}for (String str:childRecursionList) {List<String> childNodeNoList = getChildNodeNo(limitMeshList, str, childList);if (!childList.containsAll(childNodeNoList)) {childList.addAll(childNodeNoList);}}}return childList;}private List<String> getChildRecursionList(String nodeNo, List<LimitMesh> limitMeshList) {return limitMeshList.stream().filter(limitMesh -> limitMesh.getParentNode().equals(nodeNo)).map(limitMesh -> limitMesh.getChildNode()).collect(Collectors.toList());}

四、演示查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)

當(dāng)我們查詢ins父節(jié)點(diǎn)時(shí)候返回如圖：

?當(dāng)我們查詢cust子節(jié)點(diǎn)時(shí)候返回如圖：

如果大家想看完整代碼移步這里：遞歸查詢父節(jié)點(diǎn)或子節(jié)點(diǎn)

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