Java递归查询树形结构（详解）

男娘i 2023-10-02 23:18 13阅读 0赞

#### 一.数据准备 ####

数据库表结构如下所示，

INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (1, 0, '合伙企业');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (2, 0, '有限公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (3, 0, '股份有限公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (4, 0, '政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (5, 0, '行政与事业单位');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (6, 0, '协会');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (7, 0, '公益机构');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (101, 1, '有限合伙');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (102, 1, '普通合伙');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (201, 2, '一人有限公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (202, 2, '合资公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (301, 3, '上市股份公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (302, 3, '非上市股份公司');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (401, 4, '党办机构');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (402, 4, '中央政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (403, 4, '省级政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (404, 4, '市级政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (405, 4, '县区级政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (406, 4, '乡镇政府');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (501, 5, '行政机关');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (502, 5, '事业单位');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (601, 6, '行业协会');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (602, 6, '社会团体');  
INSERT INTO \`jg\_user\`.\`com\_type\`(\`type\_id\`, \`parent\_id\`, \`type\_name\`) VALUES (701, 7, '公益机构');

![d9574b976c7b433da4c651d54ef809aa.png][]

#### 二.控制层代码编写 ####

@Log(title = "查询机构类型树", businessType = BusinessType.OTHER)
        @PostMapping("/selectComTypeTrees")
        public AjaxResult selectComTypeTrees(@RequestBody ComType comType) {
            AjaxResult ajax = AjaxResult.success();
            ajax.put("comTypeTrees", comMainService.selectComTypeTrees(comType));
            return ajax;
        }

#### 三.业务层代码编写 ####

@Override
        public List<ComType> selectComTypeTrees(ComType comType) {
            List<ComType> comTypeList = comMainMapper.selectComTypeTrees(comType);
    
            List<ComType> collect = comTypeList.stream()
                    .filter(item -> item.getParentId() == 0)
                    .map(item -> {
                        item.setChildList(getChildren(item, comTypeList));
                        return item;
                    })
                    .collect(Collectors.toList());
            return collect.size() == 0 ? comTypeList : collect;
    
        }
    
    
        public static List<ComType> getChildren(ComType comType, List<ComType> comTypeList) {
            List<ComType> collect = comTypeList.stream()
                    .filter(item -> item.getParentId().equals(comType.getTypeId()))
                    .map(item -> {
                        item.setChildList(getChildren(item, comTypeList));
                        return item;
                    })
                    .collect(Collectors.toList());
            return collect;
        }

#### 四.数据库层代买编写 ####

<resultMap type="com.ruoyi.user.domain.ComType" id="ComTypeResult">
            <result property="typeId"    column="type_id"    />
            <result property="parentId"    column="parent_id"    />
            <result property="typeName"    column="type_name"    />
        </resultMap>
        <select id="selectComTypeTrees" parameterType="com.ruoyi.user.domain.ComType" resultMap="ComTypeResult">
            select type_id,parent_id,type_name from com_type
            <where>
                <if test="parentId != null and parentId != '' "> and parent_id = #{parentId}</if>
            </where>
        </select>

#### 五.测试 ####

[http://localhost:8080/user/com/selectComTypeTrees][http_localhost_8080_user_com_selectComTypeTrees]

入参：

{
        "parentId": 0
    }

出参：

{
    	"msg": "操作成功",
    	"code": 200,
    	"comTypeTrees": [
    		{
    			"typeId": 1,
    			"parentId": 0,
    			"typeName": "合伙企业",
    			"childList": [
    				{
    					"typeId": 101,
    					"parentId": 1,
    					"typeName": "有限合伙",
    					"childList": [
    						{
    							"typeId": 101001,
    							"parentId": 101,
    							"typeName": "测试三级菜单",
    							"childList": []
    						}
    					]
    				},
    				{
    					"typeId": 102,
    					"parentId": 1,
    					"typeName": "普通合伙",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 2,
    			"parentId": 0,
    			"typeName": "有限公司",
    			"childList": [
    				{
    					"typeId": 201,
    					"parentId": 2,
    					"typeName": "一人有限公司",
    					"childList": []
    				},
    				{
    					"typeId": 202,
    					"parentId": 2,
    					"typeName": "合资公司",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 3,
    			"parentId": 0,
    			"typeName": "股份有限公司",
    			"childList": [
    				{
    					"typeId": 301,
    					"parentId": 3,
    					"typeName": "上市股份公司",
    					"childList": []
    				},
    				{
    					"typeId": 302,
    					"parentId": 3,
    					"typeName": "非上市股份公司",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 4,
    			"parentId": 0,
    			"typeName": "政府",
    			"childList": [
    				{
    					"typeId": 401,
    					"parentId": 4,
    					"typeName": "党办机构",
    					"childList": []
    				},
    				{
    					"typeId": 402,
    					"parentId": 4,
    					"typeName": "中央政府",
    					"childList": []
    				},
    				{
    					"typeId": 403,
    					"parentId": 4,
    					"typeName": "省级政府",
    					"childList": []
    				},
    				{
    					"typeId": 404,
    					"parentId": 4,
    					"typeName": "市级政府",
    					"childList": []
    				},
    				{
    					"typeId": 405,
    					"parentId": 4,
    					"typeName": "县区级政府",
    					"childList": []
    				},
    				{
    					"typeId": 406,
    					"parentId": 4,
    					"typeName": "乡镇政府",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 5,
    			"parentId": 0,
    			"typeName": "行政与事业单位",
    			"childList": [
    				{
    					"typeId": 501,
    					"parentId": 5,
    					"typeName": "行政机关",
    					"childList": []
    				},
    				{
    					"typeId": 502,
    					"parentId": 5,
    					"typeName": "事业单位",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 6,
    			"parentId": 0,
    			"typeName": "协会",
    			"childList": [
    				{
    					"typeId": 601,
    					"parentId": 6,
    					"typeName": "行业协会",
    					"childList": []
    				},
    				{
    					"typeId": 602,
    					"parentId": 6,
    					"typeName": "社会团体",
    					"childList": []
    				}
    			]
    		},
    		{
    			"typeId": 7,
    			"parentId": 0,
    			"typeName": "公益机构",
    			"childList": [
    				{
    					"typeId": 701,
    					"parentId": 7,
    					"typeName": "公益机构",
    					"childList": []
    				}
    			]
    		}
    	]
    }

尽自己的一些绵薄之力，希望对大家有所帮助，谢谢！^\_^

[d9574b976c7b433da4c651d54ef809aa.png]: https://img-blog.csdnimg.cn/d9574b976c7b433da4c651d54ef809aa.png
[http_localhost_8080_user_com_selectComTypeTrees]: http://localhost:8080/user/com/selectComTypeTrees