拼接treejson数据不能显示child

public String getJSON(int parentid)
     
     {
      List alldepartment=this.queryTree(parentid);
      StringBuffer str=new StringBuffer();
      str.append("[");
      for(int i=0;i<alldepartment.size();i++){
  departmentPojo department=(departmentPojo) alldepartment.get(i);
if(department.getParent()==null)
         {
     str.append("{id:'"+department.getId()+"',text:'"+department.getText()+"',leaf:'"+department.isLeaf());
     str.append("',children:[");
     //System.out.println(department.getId());
     this.getJSON(department.getId());
     str.append("]");
     str.append("}");
     }
     else 
     {
     System.out.println("///////////////////////////////////////////////////");
     str.append("{id:'"+department.getId()+"',text:'"+department.getText()+"',leaf:'"+department.isLeaf()+"'}");
    
     }
 if (i<alldepartment.size()-1)   
{   
   str .append( ",");   
         }   
         }
str.append("]");
      
      return str.toString();
     }