根据id查询所有子节点/父节点，mysql 以及ssm前后台处理流程

 1 SELECT T2.*
 2 FROM ( 
 3         SELECT 
 4                 @r AS _id, 
 5                 (SELECT @r := parent_id FROM catelog WHERE id = _id) AS parent_id, 
 6                 @l := @l + 1 AS lvl 
 7         FROM 
 8                 (SELECT @r := 4, @l := 0) vars,
 9                 catelog h 
10         WHERE @r <> 0) T1 
11 JOIN catelog T2 
12 ON T1._id = T2.id 
13 ORDER BY T1.lvl DESC 

 1 //查询目录
 2 function findByDirectory(id){
 3     var url = 'cateLogAction!findParentMessageById.action?id='+id;
 4     $.ajax({
 5         type : 'get',
 6         url : url,
 7         dataType : 'json',
 8         global : false,
 9         async : true,
10         success : function(data) {
11             //alert(data.parentMessage);//打印测试显示内容
12             var catelogName = [];
13             for(var i=0;i<data.parentMessage.length;i++){
14                 //alert(data.parentMessage[i].name);
15                 //如果是最后的子目录，后面不加/
16                 if(i == data.parentMessage.length -1 ){
17                     var name = data.parentMessage[i].name
18                 }else{
19                     var name = data.parentMessage[i].name + "/";
20                 }
21                 catelogName += name;
22             }
23             //使用id设置值
24             $("#directory").text(catelogName);
25         }
26     });
27 }

 1 <select id="findParentMessageById" resultMap="cateLogInstanceMap">
 2 <![CDATA[
 3     SELECT T2.*
 4     FROM ( 
 5             SELECT 
 6                     @r AS _id, 
 7                     (SELECT @r := parent_id FROM catelog WHERE id = _id) AS parent_id, 
 8                     @l := @l + 1 AS lvl 
 9             FROM 
10                     (SELECT @r := 4, @l := 0) vars,
11                     catelog h 
12             WHERE @r <> 0) T1 
13     JOIN catelog T2 
14     ON T1._id = T2.id 
15     ORDER BY T1.lvl DESC 
16 ]]>
17 </select>