4

我有以下代码：

Connection conn = null;
    Statement stmt = null;

    // MySQL connection details.
    String username = ("username");
    String password = ("password");
    String url = ("jdbc:derby://localhost:1527/OnlineLibrary");

    try {

        // Connect to database. 
        Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();               
        conn = DriverManager.getConnection (url, username, password);            
        stmt = conn.createStatement();

        // Get data.
        String query = ("SELECT PersonNo, Forename, Surname FROM Person;");                       
        ResultSet rs = stmt.executeQuery(query);               
        while (rs.next()) {                
            System.out.println("Person: no: " + rs.getInt("PersonNo") + " name: " + rs.getString("Forename") + " " + rs.getString("Surname"));
        }                 

        // Disconnect from database.
        stmt.close();
        conn.close();
    }
    catch(Exception ex) {
        Java_Utils.printStackTrace("Error connecting to database", ex, true);    
    }

这给了我：

Error connecting to database
org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unknown Source)
org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
org.apache.derby.client.am.Statement.executeQuery(Unknown Source)
misc.Simple_JDBC_Test.main(Simple_JDBC_Test.java:32)

在我看来一切都很好。我可以使用连接池连接到数据库，但我不明白上述错误。

4

2 回答 2

1

@Mr Morgan，
使用 PreparedStatement 而不是 Statement，表示替换

结果集 rs = stmt.executeQuery(query);
和

ProblemStatement pStmt = dbConnection.prepareStatement(query);

结果集 r = pStmt.executeQuery();

完成此操作后请显示您的输出！

于 2014-03-14T08:54:16.797 回答
1

去掉分号；在您的陈述结束时签名：

String query = ("SELECT PersonNo, Forename, Surname FROM Person");

然后直接在您的OnLineLibrary数据库中执行相关查询以检查其输出以及其语法是否正确：

SELECT PersonNo, Forename, Surname FROM Person
于 2014-03-14T09:08:10.673 回答