公开SNS社区即时找朋友链的源代码和部署方案（续七）

Versant数据库的对象查询
Versant数据库可以支持SQL查询和NOSQL查询两种模式，以下为在查到第一个目标对象，之后采用NOSQL方式，自动执行朋友圈子遍历的例子：

VQLQuery q = new VQLQuery(
session,
DistributedDatabaseManager.getInstance().HPC_DEMO_NETWORK_NAME,
"select selfoid from com.versant.domain.Person where firstName='AAF1' and lastName='AAL1'");
//"select * from com.versant.domain.Person");

System.out.println("About to execute query, and load root object.");
VEnumeration results = q.execute();

// 创建已经走过的朋友路径，避免回环
System.out
.println("--------------------------------------------------------------------------");

long middleTime = System.currentTimeMillis();

HashSet<Person> friendSet = new HashSet<Person>();

if (results.hasMoreElements()) {
Person person = (Person) results.nextElement();

friendSet.add(person);

System.out.println("Start Person found:" + person.getFirstName()
+ "/" + person.getLastName()
+ ", about to print friend path.");

Iterator ite = person.getFriends().iterator();

System.out.print("<<<  -> " + person.getFirstName() + "/"
+ person.getLastName());

while (ite.hasNext()) {
Person aFriend = (Person) ite.next();
if (!inFriendCircle(aFriend, friendSet)) {
System.out.print("--> " + aFriend.getFirstName() + "/"
+ aFriend.getLastName());
printFriendPath("--> ", aFriend, friendSet);
}
}
System.out.println("  >>>");
} else {
System.out.println("No root person found.");
}

long endTime = System.currentTimeMillis();