关于有层级关系时返回前端树状json

结果
{
    "message": [
        {
            "children": [
                {
                    "children": [
                        {
                            "children": [
                                {
                                    "empno": "7876",
                                    "ename": "ADAMS",
                                    "mgr": "7788",
                                    "sal": "1100"
                                }
                            ],
                            "empno": "7788",
                            "ename": "SCOTT",
                            "mgr": "7566",
                            "sal": "3000"
                        },
                        {
                            "children": [
                                {
                                    "empno": "7369",
                                    "ename": "SMITH",
                                    "mgr": "7902",
                                    "sal": "800"
                                }
                            ],
                            "empno": "7902",
                            "ename": "FORD",
                            "mgr": "7566",
                            "sal": "3000"
                        }
                    ],
                    "empno": "7566",
                    "ename": "JONES",
                    "mgr": "7839",
                    "sal": "2975"
                },
                {
                    "children": [
                        {
                            "empno": "7499",
                            "ename": "ALLEN",
                            "mgr": "7698",
                            "sal": "1600"
                        },
                        {
                            "empno": "7521",
                            "ename": "WARD",
                            "mgr": "7698",
                            "sal": "1250"
                        },
                        {
                            "empno": "7654",
                            "ename": "MARTIN",
                            "mgr": "7698",
                            "sal": "1250"
                        },
                        {
                            "empno": "7844",
                            "ename": "TURNER",
                            "mgr": "7698",
                            "sal": "1500"
                        },
                        {
                            "empno": "7900",
                            "ename": "JAMES",
                            "mgr": "7698",
                            "sal": "950"
                        }
                    ],
                    "empno": "7698",
                    "ename": "BLAKE",
                    "mgr": "7839",
                    "sal": "2850"
                },
                {
                    "children": [
                        {
                            "empno": "7934",
                            "ename": "MILLER",
                            "mgr": "7782",
                            "sal": "1300"
                        }
                    ],
                    "empno": "7782",
                    "ename": "CLARK",
                    "mgr": "7839",
                    "sal": "2450"
                }
            ],
            "empno": "7839",
            "ename": "KING",
            "mgr": "0",
            "sal": "5000"
        }
    ]
}

1：数据库为Oracle的emp表找出King的所有下属

<select id="testBigDecimal25"  resultType="com.mayi.vo.Menu">
		select empno, ename, sal, mgr from emp
</select>

　　

一个javaBean 

public class Menu {
     private String empno;
        private String ename;
        private String sal;
        private String mgr;
        
        //菜单标识
       // private Meta meta;
     
        //子菜单
        private List<Menu> children;


get set自补

递归查子

public JSONObject getInfo() {
	System.out.println("iiiii");
	List<Menu>	list=dao.testBigDecimal24(s1.concat(".testBigDecimal25"), null);
	System.out.println(list);
	
	//调用TreeTest工具类方法生成树形结构的List集合
    List<Menu> treeList = TreeUtil.listToTree(list);

    //使用fastjson对树形list件序列化转成json字符串,过滤掉属性值为null的属性
    String message = JSON.toJSONString(treeList,SerializerFeature.PrettyFormat);
    JSONObject returnData = new JSONObject();

    //重新将json字符串转成jsonObject对象,返回给前端
    returnData.put("message",JSON.parse(message));
    //return CommonUtil.successJson(returnData);

		return returnData;
		
	}

　　utils

//用List构建带有层次结构的json数据
//List父子节点构造树形Json
public class TreeUtil {
  //将list集合转成树形结构的list集合
  public static List<Menu> listToTree(List<Menu> list) {
      //用递归找子。
      List<Menu> treeList = new ArrayList<Menu>();
      for (Menu tree : list) {
          if (tree.getMgr().equals("0")) {      //这个地方注意报空指针======
              treeList.add(findChildren(tree, list));
          }
      }
      return treeList;
  }

  //寻找子节点
  private static Menu findChildren(Menu tree, List<Menu> list) {
      for (Menu node : list) {
          if (node.getMgr().equals(tree.getEmpno())) {
              if (tree.getChildren() == null) {
                  tree.setChildren(new ArrayList<Menu>());
              }
              tree.getChildren().add(findChildren(node, list));
          }
      }
      return tree;
  }


}