第一步：準備表結構及對應的表資料

1.表結構

create table City
(
id char(32) not null,
name varchar2(30),
parent_id char(32) //父級欄位
)

2.插入資料

insert into City (id, name, parent_id) values (1, '書籍', 0);
insert into City (id, name, parent_id) values (2, '科普書籍', 1);
insert into City (id, name, parent_id) values (3, '教科書籍', 1);
insert into City (id, name, parent_id) values (4, '童話書籍', 1);
insert into City (id, name, parent_id) values (5, '語文', 3);
insert into City (id, name, parent_id) values (6, '數學', 3);
insert into City (id, name, parent_id) values (7, '九年級上冊語文書', 5);
insert into City (id, name, parent_id) values (8, '九年級下冊語文書', 5);
insert into City (id, name, parent_id) values (9, '九年級上冊數學書', 6);
insert into City (id, name, parent_id) values (10, '九年級下冊數學書', 6);
insert into City (id, name, parent_id) values (11, '十萬個為什麼', 2);
insert into City (id, name, parent_id) values (12, '格林童話', 4);

第二步：建立Entity的Bean物件

1.建立Bean

public class CityEntity  implements Serializable {
private String id;
private String name;
private String parent_id;

//getter，setter
}

2.建立對外輸出的響應Bean

public class CityResponse {
    private String id;
    private String name;
    private String parent_id;
    private List children = new ArrayList();

    //getter，setter
    public CityResponse() {
    }

    public CityResponse(CityEntity entity) {
        this.set(entity);
    }

    public CityResponse set(CityEntity entity) {
        this.id = entity.getId;
        this.name = entity.getName;
        this.parentId = entity.getParentId;

        return this;
    }
}

第三步 進行遞迴遍歷，生成樹形介面

1.測試程式碼：

public class CityTest {
@Test
public void cityTree() throws Exception{
System.out.println(recursiveTree(1));
}

2.遞迴方法

 public CityResponse getTreeModule(String id) throws Exception {
        CityResponse firstTreeResponse = new CityResponse();
        //根據id獲取節點物件(SELECT * FROM City c WHERE c.id=?)
        CityEntity entity = cityService.findById(id);
        firstTreeResponse.set(entity);
        //查詢id下的所有子節點(SELECT * FROM City c WHERE c.parent_id=?)
        List<CityEntity> entities = cityService.findByParentId(id);
        List<CityResponse> treeResponses = new ArrayList<CityResponse>();
        CityResponse secondTreeResponse = null;
        for (CityEntity cityEntity : entities) {
            secondTreeResponse = new CityResponse();
            treeResponses.add(secondTreeResponse.set(CityEntity));
        }
        CityResponse cityTreeResponse = null;
        for (CityResponse child : treeResponses) {
             cityTreeResponse = getTreeModule(child.getId());//開始遞迴
            firstTreeResponse.getChildren().add(cityTreeResponse);
        }
        return firstTreeResponse;
    }

3.輸出(省略)