我有一个非常基本的代码位,执行select查询并返回一个布尔值,取决于结果集是否为空。在Java中,ResultSet可以为'null'吗?
public boolean checkIfUserHasPreferences(String username){
ResultSet rs = null;
boolean checkBoolean = false;
try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
con = DriverManager.getConnection(Messages.getString("OracleUserManagement.0"), Messages.getString("OracleUserManagement.1"), Messages.getString("OracleUserManagement.2")); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
PreparedStatement statement = con.prepareStatement("SELECT USERNAME FROM USER_PREFERENCES WHERE USERNAME = ?");
statement.setString(1, username);
rs = statement.executeQuery();
if (rs == null){
System.out.println("I checked it was true!");
checkBoolean = true;
} else {
System.out.println("I checked it was false!");
checkBoolean = false;
}
con.commit();
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
return checkBoolean;
}
令我困惑的是,即使表格/数据库为空,它总是打印出“我检查它是假的!”。
这是因为即使结果集返回0行,它不= null?我应该使用while(rs.next())来检查吗?
谢谢。我从来没有真正阅读API,我想我应该更频繁地这样做... – DeaIss
@oOTesterOo。当然。遇到问题时,您应该首先访问API。这就是他们在那里。 –