Question

我想知道使用BoundStatement优于PreparedStatement的优势是什么？

PreparedStatement statement = session.prepare(
                      "INSERT INTO simplex.songs " +
                      "(id, title, album, artist) " +
                      "VALUES (?, ?, ?, ?);");

BoundStatement boundStatement = new BoundStatement(statement);
            session.execute(boundStatement.bind(
                  UUID.fromString("756716f7-2e54-4715-9f00-91debea6cf50"),
                  "La Petite Tonkinoise",
                  "Bye Bye Blackbird",
                  "Joséphine Baker");

最简单的方法是：

PreparedStatement ps = session.prepare(
                      "INSERT INTO simplex.songs " +
                      "(id, title, album, artist, tags) " +
                      "VALUES (?, ?, ?, ?, ?);");
ps.bind(UUID.fromString("756716f7-2e54-4715-9f00-91debea6cf50"),
                      "La Petite Tonkinoise",
                      "Bye Bye Blackbird",
                      "Joséphine Baker");

如您所见，我可以在没有preparedStatement的情况下将数据绑定到boundStatements。 boundStatement在哪里有用？

Answer 1

没有优势：BoundStatement只不过是带有变量限制的PreparedStatement。事实上，PreparedStatements的bind()方法返回BoundStatement。

Answer 2

对我来说，在PreparedStatement上调用bind（...）时会自动创建BoundStatement。您也可以直接创建实例BoundStatement。

PreparedStatement和BoundStatement具有不同的行为，因为PreparedStatement.bind（）返回新实例BoundStatement，而BoundStatement.bind（）返回自己。

这是多线程环境中的重要细节。在共享的BoundStatement结果危险上调用方法.bind（）

// shared instance BoundStatement on few threads 
BoundStatement bs1 = 
// bs2 is the same as bs1
// param1, param2, ... are different for every thread
BoundStatement bs2 = bs1.bind(param1, param2, ...);
// add some time to wait so other thread can modify your params
// Thread.sleep(RandomUtils.nextInt(100));        
// result2 sometimes may be with incorrect result 
results2 = session.execute(bs2);

当您在PreparedStatement上调用bind时，您将获得不同的对象实例，并且它是线程安全的。（与上述相同）

PreparedStatement ps1 = 
BoundStatement bs2 = ps1.bind(param1, param2, ...);
results2 = session.execute(bs2);

准备语句与Cassandra中的Bound语句？

2 个答案: