java - 准备好的语句从数据库填充列表

Question

您好，我正在尝试从数据库中获取所有值并将它们存储到列表中。 每行值都放入一个对象中，然后存储在一个列表中。

我应该如何使用准备好的语句或语句来执行此操作？

这是我当前的伪代码

    Class.forName("com.mysql.jdbc.Driver");
        Connection connection = DriverManager.getConnection(url, username, password);

        PreparedStatement st = connection.prepareStatement("SELECT * FROM People");

        List People = new List();

       while (st.next()) 
        {
         Person newPerson = new Person();
         newPerson.firstName = rset.getString("first_name");
         newPerson.lastName  = rset.getString("last_name");
         newPerson.email     = rset.getString("email");
         People.add(newPerson);
          }

Answer 1

一般来说:

1. 应用程序启动 -> 打开连接
2. 在某些方法上打开语句并获取结果集
3. 关闭 stmt(或重新使用它)并关闭结果集(如果错误关闭)
4. 应用程序停止 -> 关闭连接

在管理这些资源方面，java 6 和 java 7 之间存在一些差异。

Java 6

            Class.forName("com.mysql.jdbc.Driver");
        Connection connection = DriverManager.getConnection(url, usr,
                pwd);

            //.....

        PreparedStatement st=null;
        ResultSet rset=null;
        try {
            st = connection
                    .prepareStatement("SELECT first_name,last_name,email FROM People");

            List<Person> peoples = new ArrayList<Person>();

            rset = st.executeQuery();

            while (rset.next()) {
                Person newPerson = new Person();
                newPerson.firstName = rset.getString("first_name");
                newPerson.lastName = rset.getString("last_name");
                newPerson.email = rset.getString("email");
                peoples.add(newPerson);
            }

        } finally {

            try {
                rset.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                st.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }

Java 7

            Class.forName("com.mysql.jdbc.Driver");
    Connection connection = DriverManager.getConnection("", "", "");
             //.....

    try (PreparedStatement st = connection
            .prepareStatement("SELECT first_name,last_name,email FROM People")) {

        List<Person> peoples = new ArrayList<>(); // but should be new ArrayList<Person>();

        try (ResultSet rset = st.executeQuery()) {

            while (rset.next()) {
                Person newPerson = new Person();
                newPerson.firstName = rset.getString("first_name");
                newPerson.lastName = rset.getString("last_name");
                newPerson.email = rset.getString("email");
                peoples.add(newPerson);
            }
        }
    }

注意:我没有管理连接，因为它在应用程序启动结束时正常打开和关闭。

注意:钻石<> java 7 way