java树结构查询

妖狐艹你老母 2023-10-12 21:34 14阅读 0赞

> 简单表结构示例：

![77ad557e95c14b27b01f9d6b09ee5b0f.png][]

> 结果展示：

> 实体类TestTree

@Data
    @TableName("test_tree")
    @Accessors(chain = true)
    @ApiModel(value="测试树", description="测试树")
    public class TestTree {
    
        @ApiModelProperty(value = "ID")
        private Integer id;
    
        @ApiModelProperty(value = "父id")
        private Integer pid;
    
        @ApiModelProperty(value = "姓名")
        private String name;
    
        @ApiModelProperty(value = "编码")
        private String code;
    
        @TableField(exist = false)
        private List<TestTree> children;
    
    }

> controller

@Slf4j
    @Api(tags = "测试树")
    @RestController
    @RequestMapping("/test")
    public class TestTreeController {
    	@Resource
    	private TestTreeService testTreeService;
    
    	@ApiOperation(value = "测试树",notes = "测试树")
    	@GetMapping("/selectTree")
    	public Result<Object> selectTree() {
    		Result<Object> result = testTreeService.selectTree();
    		return Result.ok(result);
    	}
    }

> service

public interface TestTreeService {
        Result<Object> selectTree();
    
    }
    
    
    @Service
    public class TestTreeServiceImpl implements TestTreeService {
        @Resource
        private TestTreeMapper testTreeMapper;
    
        @Override
        public Result<Object> selectTree() {
            List<TestTree> testTreeList=this.testTreeMapper.selectTree();
    
            List<TestTree> testTrees = testTreeList.stream().filter(testTree -> 0 == testTree.getPid())
                    .peek(testTree -> testTree.setChildren(createChildList(testTree, testTreeList)))
                    .collect(Collectors.toList());
            return Result.ok(testTrees);
        }
    
        /**
         * @param testTree  父级
         * @param testTreeList 对应的list
         * @return
         */
        private static List<TestTree> createChildList(TestTree testTree, List<TestTree> testTreeList) {
    
            return testTreeList.stream().filter(model -> testTree.getId().equals(model.getPid()))
                    .peek(model -> model.setChildren(createChildList(model, testTreeList)))
                    .collect(Collectors.toList());
        }
    
    }

> mapper

sql：select \* from test\_tree

> 多层次使用此方法也可以查询出树形结构

示例：

![8a371681c69944129f3ce8a45c19007f.png][]

{
        "success": true,
        "message": "操作成功！",
        "code": 200,
        "result": [
          {
            "id": 1,
            "pid": 0,
            "name": "中国",
            "code": "0001",
            "children": [
              {
                "id": 2,
                "pid": 1,
                "name": "河南",
                "code": "0002",
                "children": [
                  {
                    "id": 4,
                    "pid": 2,
                    "name": "周口",
                    "code": "0021",
                    "children": [
                      {
                        "id": 10,
                        "pid": 4,
                        "name": "郸城县",
                        "code": "0211",
                        "children": [
                          {
                            "id": 12,
                            "pid": 10,
                            "name": "汲冢镇",
                            "code": "2111",
                            "children": []
                          },
                          {
                            "id": 13,
                            "pid": 10,
                            "name": "李楼乡",
                            "code": "2112",
                            "children": []
                          }
                        ]
                      },
                      {
                        "id": 11,
                        "pid": 4,
                        "name": "沈丘县",
                        "code": "0212",
                        "children": []
                      }
                    ]
                  },
                  {
                    "id": 5,
                    "pid": 2,
                    "name": "郑州",
                    "code": "0022",
                    "children": []
                  }
                ]
              },
              {
                "id": 3,
                "pid": 1,
                "name": "台湾",
                "code": "0003",
                "children": [
                  {
                    "id": 6,
                    "pid": 3,
                    "name": "台北",
                    "code": "0031",
                    "children": []
                  }
                ]
              },
              {
                "id": 7,
                "pid": 1,
                "name": "北京",
                "code": "0004",
                "children": []
              }
            ]
          },
          {
            "id": 8,
            "pid": 0,
            "name": "俄罗斯",
            "code": "1001",
            "children": [
              {
                "id": 9,
                "pid": 8,
                "name": "莫斯科",
                "code": "1011",
                "children": []
              }
            ]
          }
        ],
      "resultTwo": null,
      "resultThree": null,
      "timestamp": 1687766628068
    }

[77ad557e95c14b27b01f9d6b09ee5b0f.png]: https://img-blog.csdnimg.cn/77ad557e95c14b27b01f9d6b09ee5b0f.png
[8a371681c69944129f3ce8a45c19007f.png]: https://img-blog.csdnimg.cn/8a371681c69944129f3ce8a45c19007f.png