公开分布式高性能查询的源代码和部署方案(三）
7）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();