SpringBoot：查询Tree形数据

桃扇骨 2022-12-23 07:25 216阅读 0赞

我们最终是想查询一个类似于以下结构的数据，用于ElementUI或iView等组件库  
![在这里插入图片描述][20201124082908972.png_pic_center]  
这是数据库内的存储结构(projectId作为查询条件，可忽略)  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70_pic_center]

首先是两个实体类，`TestCaseNodeDO`与`TreeBO`

*  TestCaseNodeDO

public class TestCaseNodeDO { 
    
    
        /** * 节点id */
        private Integer id;
    	
    	private Integer projectId;
    
        /** * Node name */
        private String name;
    
        /** * 父节点id */
        private Integer parentId;
    
        /** * 节点level */
        private Integer level;
    
        /** * 创建时间 */
        @JsonFormat(locale="zh", timezone="GMT+8", pattern="yyyy-MM-dd HH:mm:ss")
        private Date createTime;
    
        /** * 更新时间 */
        @JsonFormat(locale="zh", timezone="GMT+8", pattern="yyyy-MM-dd HH:mm:ss")
        private Date updateTime;
    }

*  TreeBO

public class TreeBO { 
    
        private Integer id;
    
        private String name;
    
        private Integer level;
    
        private List<TreeBO> children;
    }

*  Service

@Override
    publicList<TreeBO> selectNodeTreeByProjectId(Integer projectId) { 
    	// 先从数据库中查询所有数据，保存为list
        List<TestCaseNodeDO> nodeList = new LambdaQueryChainWrapper<>(testCaseNodeMapper)
                .eq(TestCaseNodeDO::getProjectId, projectId)
                .list();
    	// 最终的返回结果
        List<TreeBO> treeList = new ArrayList<>();
        // 将单层的TestCaseNodeDO变成以level为key的多层map, [A1,A2,A3,B1]-> {1:[A1,B1],2:[A2],3:[A3]} 
        Map<Integer, List<TestCaseNodeDO>> nodeLevelMap = new HashMap<>();
    
        nodeList.forEach(node -> { 
            Integer level = node.getLevel();
            if (nodeLevelMap.containsKey(level)) { 
                nodeLevelMap.get(level).add(node);
            } else { 
                List<TestCaseNodeDO> testCaseNodes = new ArrayList<>();
                testCaseNodes.add(node);
                nodeLevelMap.put(node.getLevel(), testCaseNodes);
            }
        });
    
        List<TestCaseNodeDO> rootNodes = Optional.ofNullable(nodeLevelMap.get(1)).orElse(new ArrayList<>());
        rootNodes.forEach(rootNode -> treeList.add(buildNodeTree(nodeLevelMap, rootNode)));
    
        return treeList;
    }
    
    /** * 递归构建节点树 * @param nodeLevelMap * @param rootNode * @return */
    private TreeBO buildNodeTree(Map<Integer, List<TestCaseNodeDO>> nodeLevelMap, TestCaseNodeDO rootNode) { 
    
        TreeBO nodeTree = new TreeBO();
        BeanUtils.copyProperties(rootNode, nodeTree);
        nodeTree.setName(rootNode.getName());
    
        List<TestCaseNodeDO> lowerNodes = nodeLevelMap.get(rootNode.getLevel() + 1);
        if (lowerNodes == null) { 
            return nodeTree;
        }
    
        List<TreeBO> children = Optional.ofNullable(nodeTree.getChildren()).orElse(new ArrayList<>());
    
        lowerNodes.forEach(node -> { 
            if (node.getParentId() != null && node.getParentId().equals(rootNode.getId())) { 
                children.add(buildNodeTree(nodeLevelMap, node));
                nodeTree.setChildren(children);
            }
        });
    
        return nodeTree;
    }

然后我们可以得到这样的json数据，前端可以直接使用了！  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70_pic_center 1]

[20201124082908972.png_pic_center]: /images/20221120/6d23aa8d2f7c4224a2f5d429389a998a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70_pic_center]: /images/20221120/7f3916ca083c47c0bdd2f80eaaa23e99.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221120/8ec05a768f644e02b501066533a4d4ac.png