java树形结构 算法

最近看到一个有意思的树形结构，为每个节点添加了lft
和
rgt
两个属性。这样查找该节点的子节点、
查找该节点所有父节点，就不用去递归查询，只需要用
between
、
and
语句就可以实现。下面以创建一个栏目树为例，以下是我的理解。

　　一般来讲，我们创建栏目树的时候，大多只需要一个外键parentid

来区分该节点属于哪个父节点。数据库的设计如下图：



这样一来，

1.查找该节点的所有子节点，则需要采用
sql
的递归语句：

Sql代码

select
*
from
tableName
connect

by

prior
id=sj_parent_id start
with
id=1

select * from tableName connect by prior id=sj_parent_id start with  id=1

(
oracle 写法，
mysql
目前不支持，如果
mysql
想查找树形，可以利用存储过程

).

2.查找该节点的父节点
的
sql
递归语
句：

Sql代码

select
*
from
tableName
connect

by

prior
sj_parent_id =id start
with
id=1

select * from tableName connect by prior sj_parent_id =id start with  id=1

　如果数据量过大或者层次太多，那么这样操作是会影响性能的。

　
　“任何树形结构都可以用二叉树来表示”。其实我们创建的栏目树就是一个简型的二叉树。根据数据结构里面二叉树的遍历，再稍微修改下，将数据库设计如下图
所示：



这样我们查找该节点的所有子节点，则只需要查找id
在
lft
和
rgt
之间的所有节点即可。

1.查找该节点的所有子节点的

S
ql语句为：

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Sql代码

select
*
from
tb_subject s,tb_subject t
where
s.lft
between
t.lft
and
t.rgt
and
t.id=1

select * from tb_subject s,tb_subject t where s.lft between t.lft and t.rgt and t.id=1

2.查找该节点的所有父节点的
sql
语句为：

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Sql代码

select
s.*
from
tb_subject s,tb_subject t
where
s.lft<t.lft
and
(s.rgt-s.lft)>1
and
s.rgt>t.rgt
and
t.id=1

select s.* from tb_subject s,tb_subject t where s.lft<t.lft and (s.rgt-s.lft)>1 and s.rgt>t.rgt and t.id=1

　下面来详细讲解下，怎么用java
来实现这种算法。

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　1.
新增节点

　新增节点比较简单，基本步骤为

　A．
查找当前插入节点的父节点的lft
值

　B．
将树形中所有lft
和
rgt
节点大于父节点左值的节点都
+2

　C．
将父节点左值+1
，左值
+2
分别作为当前节点的
lft
和
rgt

　因为项目中采用的是struts2+hibernate3.2+spring2.5
的框架，代码如下：

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Java代码

public

boolean
onSave(Object entity, Serializable id, Object[] state,

String[] propertyNames, Type[] types) {

if
(entity
instanceof
HibernateTree) {

HibernateTree tree = (HibernateTree) entity;

Long parentId = tree.getParentId();

String beanName = tree.getClass().getName();

Session session = getSession();

FlushMode model = session.getFlushMode();

session.setFlushMode(FlushMode.MANUAL);

Integer myPosition = new
Integer(
0
);

//查找父节点的左值

if
(parentId !=
null
) {

String hql = "select b.lft from "
+ beanName

+ " b where b.id=:pid"
;

myPosition = (Integer) session.createQuery(hql).setLong("pid"
,

parentId).uniqueResult();

}

//将树形结构中所有大于父节点左值的右节点+2

String hql1 = "update "
+ beanName

+ " b set b.rgt = b.rgt + 2 WHERE b.rgt > :myPosition"
;

//将树形结构中所有大于父节点左值的左节点+2

String hql2 = "update "
+ beanName

+ " b set b.lft = b.lft + 2 WHERE b.lft > :myPosition"
;

if
(!StringUtils.isBlank(tree.getTreeCondition())) {

hql1 += " and ("
+ tree.getTreeCondition() +
")"
;

hql2 += " and ("
+ tree.getTreeCondition() +
")"
;

}

session.createQuery(hql1).setInteger("myPosition"
, myPosition)

.executeUpdate();

session.createQuery(hql2).setInteger("myPosition"
, myPosition)

.executeUpdate();

session.setFlushMode(model);

//定位自己的左值(父节点左值+1)和右值(父节点左值+2)

for
(
int
i =
0
; i < propertyNames.length; i++) {

if
(propertyNames[i].equals(HibernateTree.LFT)) {

state[i] = myPosition + 1
;

}

if
(propertyNames[i].equals(HibernateTree.RGT)) {

state[i] = myPosition + 2
;

}

}

return

true
;

}

return

false
;

}

public boolean onSave(Object entity, Serializable id, Object[] state,
String[] propertyNames, Type[] types) {
if (entity instanceof HibernateTree) {
HibernateTree tree = (HibernateTree) entity;
Long parentId = tree.getParentId();
String beanName = tree.getClass().getName();
Session session = getSession();
FlushMode model = session.getFlushMode();
session.setFlushMode(FlushMode.MANUAL);
Integer myPosition = new Integer(0);
//查找父节点的左值
if (parentId != null) {
String hql = "select b.lft from " + beanName
+ " b where b.id=:pid";
myPosition = (Integer) session.createQuery(hql).setLong("pid",
parentId).uniqueResult();
}
//将树形结构中所有大于父节点左值的右节点+2
String hql1 = "update " + beanName
+ " b set b.rgt = b.rgt + 2 WHERE b.rgt > :myPosition";
//将树形结构中所有大于父节点左值的左节点+2
String hql2 = "update " + beanName
+ " b set b.lft = b.lft + 2 WHERE b.lft > :myPosition";
if (!StringUtils.isBlank(tree.getTreeCondition())) {
hql1 += " and (" + tree.getTreeCondition() + ")";
hql2 += " and (" + tree.getTreeCondition() + ")";
}
session.createQuery(hql1).setInteger("myPosition", myPosition)
.executeUpdate();
session.createQuery(hql2).setInteger("myPosition", myPosition)
.executeUpdate();
session.setFlushMode(model);
//定位自己的左值(父节点左值+1)和右值(父节点左值+2)
for (int i = 0; i < propertyNames.length; i++) {
if (propertyNames[i].equals(HibernateTree.LFT)) {
state[i] = myPosition + 1;
}
if (propertyNames[i].equals(HibernateTree.RGT)) {
state[i] = myPosition + 2;
}

}
return true;
}
return false;
}

　２.

修改节点

　
　修改的时候比较麻烦，具体步骤为：

　　在修改lft
和
rgt
之前，当前节点的父节点
id
已经改变

a.
查出当前节点的左右节点（nodelft
、
nodergt
），并
nodergt-nodelft+1 = span
，获取父节点的左节点
parentlft

b.
将所有大于parentlft
的
lft(
左节点
)
、
rgt(
右节点
)
的值
+span

c.
查找当前节点的左右节点（nodelft
、
nodergt
），并
parentlft-nodelft+1 = offset

d.
将所有lft(
左节点
) between nodelft and nodergt
的值
+offset

e.
将所有大于nodergt
的
lft(
左节点
)
、
rgt(
右节点
)
的值
-span

　J
ava代码如下：

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Java代码

public

void
updateParent(HibernateTree tree, HibernateTree preParent,

HibernateTree curParent) {

if
(preParent !=
null
&& preParent !=
null

&& !preParent.equals(curParent)) {

String beanName = tree.getClass().getName();

// 获得节点位置

String hql = "select b.lft,b.rgt from "
+ beanName

+ " b where b.id=:id"
;

Object[] position = (Object[]) super
.createQuery(hql).setLong(

"id"
, tree.getId()).uniqueResult();

System.out.println(hql+"| id = "
+tree.getId());

int
nodeLft = ((Number) position[
0
]).intValue();

int
nodeRgt = ((Number) position[
1
]).intValue();

int
span = nodeRgt - nodeLft +
1
;

// 获得当前父节点左位置

hql = "select b.lft from "
+ beanName +
" b where b.id=:id"
;

int
parentLft = ((Number)
super
.createQuery(hql).setLong(
"id"
,

curParent.getId()).uniqueResult()).intValue();

System.out.println(hql+"| id = "
+curParent.getId());

// 先空出位置

String hql1 = "update "
+ beanName +
" b set b.rgt = b.rgt + "

+ span + " WHERE b.rgt > :parentLft"
;

String hql2 = "update "
+ beanName +
" b set b.lft = b.lft + "

+ span + " WHERE b.lft > :parentLft"
;

if
(!StringUtils.isBlank(tree.getTreeCondition())) {

hql1 += " and ("
+ tree.getTreeCondition() +
")"
;

hql2 += " and ("
+ tree.getTreeCondition() +
")"
;

}

super
.createQuery(hql1).setInteger(
"parentLft"
, parentLft)

.executeUpdate();

super
.createQuery(hql2).setInteger(
"parentLft"
, parentLft)

.executeUpdate();

System.out.println(hql1+"| parentLft = "
+parentLft);

System.out.println(hql2+"| parentLft = "
+parentLft);

// 再调整自己

hql = "select b.lft,b.rgt from "
+ beanName +
" b where b.id=:id"
;

position = (Object[]) super
.createQuery(hql).setLong(
"id"
,

tree.getId()).uniqueResult();

System.out.println(hql+"| id = "
+tree.getId());

nodeLft = ((Number) position[0
]).intValue();

nodeRgt = ((Number) position[1
]).intValue();

int
offset = parentLft - nodeLft +
1
;

hql = "update "

+ beanName

+ " b set b.lft=b.lft+:offset, b.rgt=b.rgt+:offset WHERE b.lft between :nodeLft and :nodeRgt"
;

if
(!StringUtils.isBlank(tree.getTreeCondition())) {

hql += " and ("
+ tree.getTreeCondition() +
")"
;

}

super
.createQuery(hql).setParameter(
"offset"
, offset)

.setParameter("nodeLft"
, nodeLft).setParameter(
"nodeRgt"
,

nodeRgt).executeUpdate();

System.out.println(hql+"| offset = "
+offset+
" | nodelft = "
+nodeLft+
" | nodergt = "
+ nodeRgt);

// 最后删除（清空位置）

hql1 = "update "
+ beanName +
" b set b.rgt = b.rgt - "
+ span

+ " WHERE b.rgt > :nodeRgt"
;

hql2 = "update "
+ beanName +
" b set b.lft = b.lft - "
+ span

+ " WHERE b.lft > :nodeRgt"
;

if
(tree.getTreeCondition() !=
null
) {

hql1 += " and ("
+ tree.getTreeCondition() +
")"
;

hql2 += " and ("
+ tree.getTreeCondition() +
")"
;

}

super
.createQuery(hql1).setParameter(
"nodeRgt"
, nodeRgt)

.executeUpdate();

super
.createQuery(hql2).setParameter(
"nodeRgt"
, nodeRgt)

.executeUpdate();

System.out.println(hql1+"| nodeRgt = "
+nodeRgt);

System.out.println(hql2+"| nodeRgt = "
+nodeRgt);

}

}

public void updateParent(HibernateTree tree, HibernateTree preParent,
HibernateTree curParent) {
if (preParent != null && preParent != null
&& !preParent.equals(curParent)) {
String beanName = tree.getClass().getName();
// 获得节点位置
String hql = "select b.lft,b.rgt from " + beanName
+ " b where b.id=:id";
Object[] position = (Object[]) super.createQuery(hql).setLong(
"id", tree.getId()).uniqueResult();
System.out.println(hql+"| id = "+tree.getId());
int nodeLft = ((Number) position[0]).intValue();
int nodeRgt = ((Number) position[1]).intValue();
int span = nodeRgt - nodeLft + 1;
// 获得当前父节点左位置
hql = "select b.lft from " + beanName + " b where b.id=:id";
int parentLft = ((Number) super.createQuery(hql).setLong("id",
curParent.getId()).uniqueResult()).intValue();

System.out.println(hql+"| id = "+curParent.getId());
// 先空出位置
String hql1 = "update " + beanName + " b set b.rgt = b.rgt + "
+ span + " WHERE b.rgt > :parentLft";
String hql2 = "update " + beanName + " b set b.lft = b.lft + "
+ span + " WHERE b.lft > :parentLft";
if (!StringUtils.isBlank(tree.getTreeCondition())) {
hql1 += " and (" + tree.getTreeCondition() + ")";
hql2 += " and (" + tree.getTreeCondition() + ")";
}
super.createQuery(hql1).setInteger("parentLft", parentLft)
.executeUpdate();
super.createQuery(hql2).setInteger("parentLft", parentLft)
.executeUpdate();

System.out.println(hql1+"| parentLft = "+parentLft);
System.out.println(hql2+"| parentLft = "+parentLft);

// 再调整自己
hql = "select b.lft,b.rgt from " + beanName + " b where b.id=:id";
position = (Object[]) super.createQuery(hql).setLong("id",
tree.getId()).uniqueResult();
System.out.println(hql+"| id = "+tree.getId());
nodeLft = ((Number) position[0]).intValue();
nodeRgt = ((Number) position[1]).intValue();
int offset = parentLft - nodeLft + 1;
hql = "update "
+ beanName
+ " b set b.lft=b.lft+:offset, b.rgt=b.rgt+:offset WHERE b.lft between :nodeLft and :nodeRgt";
if (!StringUtils.isBlank(tree.getTreeCondition())) {
hql += " and (" + tree.getTreeCondition() + ")";
}
super.createQuery(hql).setParameter("offset", offset)
.setParameter("nodeLft", nodeLft).setParameter("nodeRgt",
nodeRgt).executeUpdate();
System.out.println(hql+"| offset = "+offset+" | nodelft = "+nodeLft+" | nodergt = "+ nodeRgt);
// 最后删除（清空位置）
hql1 = "update " + beanName + " b set b.rgt = b.rgt - " + span
+ " WHERE b.rgt > :nodeRgt";
hql2 = "update " + beanName + " b set b.lft = b.lft - " + span
+ " WHERE b.lft > :nodeRgt";
if (tree.getTreeCondition() != null) {
hql1 += " and (" + tree.getTreeCondition() + ")";
hql2 += " and (" + tree.getTreeCondition() + ")";
}
super.createQuery(hql1).setParameter("nodeRgt", nodeRgt)
.executeUpdate();
super.createQuery(hql2).setParameter("nodeRgt", nodeRgt)
.executeUpdate();
System.out.println(hql1+"| nodeRgt = "+nodeRgt);
System.out.println(hql2+"| nodeRgt = "+nodeRgt);

}
}

　３.
删除节点

　删除节点也比较简单，具体步骤为：

　A．
查找要删除节点的lft
值

　B．
将所有lft
和
rgt
大于删除节点
lft
值的都
-2

　J
ava代码如下：

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Java代码

public

void
onDelete(Object entity, Serializable id, Object[] state,

String[] propertyNames, Type[] types) {

if
(entity
instanceof
HibernateTree) {

HibernateTree tree = (HibernateTree) entity;

String beanName = tree.getClass().getName();

Session session = getSession();

FlushMode model = session.getFlushMode();

session.setFlushMode(FlushMode.MANUAL);

//查找要删除的节点的左值

String hql = "select b.lft from "
+ beanName +
" b where b.id=:id"
;

Integer myPosition = (Integer) session.createQuery(hql).setLong(

"id"
, tree.getId()).uniqueResult();

//将所有大于删除节点左值的rgt都-2

String hql1 = "update "
+ beanName

+ " b set b.rgt = b.rgt - 2 WHERE b.rgt > :myPosition"
;

//将所有大于删除节点左值的lft都-2

String hql2 = "update "
+ beanName

+ " b set b.lft = b.lft - 2 WHERE b.lft > :myPosition"
;

if
(tree.getTreeCondition() !=
null
) {

hql1 += " and ("
+ tree.getTreeCondition() +
")"
;

hql2 += " and ("
+ tree.getTreeCondition() +
")"
;

}

session.createQuery(hql1).setInteger("myPosition"
, myPosition)

.executeUpdate();

session.createQuery(hql2).setInteger("myPosition"
, myPosition)

.executeUpdate();

session.setFlushMode(model);

}

}

public void onDelete(Object entity, Serializable id, Object[] state,
String[] propertyNames, Type[] types) {
if (entity instanceof HibernateTree) {
HibernateTree tree = (HibernateTree) entity;
String beanName = tree.getClass().getName();
Session session = getSession();
FlushMode model = session.getFlushMode();
session.setFlushMode(FlushMode.MANUAL);
//查找要删除的节点的左值
String hql = "select b.lft from " + beanName + " b where b.id=:id";
Integer myPosition = (Integer) session.createQuery(hql).setLong(
"id", tree.getId()).uniqueResult();
//将所有大于删除节点左值的rgt都-2
String hql1 = "update " + beanName
+ " b set b.rgt = b.rgt - 2 WHERE b.rgt > :myPosition";
//将所有大于删除节点左值的lft都-2
String hql2 = "update " + beanName
+ " b set b.lft = b.lft - 2 WHERE b.lft > :myPosition";
if (tree.getTreeCondition() != null) {
hql1 += " and (" + tree.getTreeCondition() + ")";
hql2 += " and (" + tree.getTreeCondition() + ")";
}
session.createQuery(hql1).setInteger("myPosition", myPosition)
.executeUpdate();
session.createQuery(hql2).setInteger("myPosition", myPosition)
.executeUpdate();
session.setFlushMode(model);
}
}

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