您沒有將某些內(nèi)容傳遞給servlet.你只需讓servlet訪問一些東西.

您應(yīng)該擺脫main()方法并將數(shù)據(jù)庫交互代碼移動到DAO類中.我還給模型類(帶有時區(qū)和位置)一個以大寫字母開頭的更敏感的名稱.總而言之,您應(yīng)該更新代碼,使其看起來如下所示：

模型類,區(qū)域(只要它有意義,任意你想要的名稱),它應(yīng)該只代表一個實體：

public class Area {

private String location;

private String timezone;

public String getLocation() { return location; }

public String getTimezone() { return timezone; }

public void setLocation(String location) { this.location = location; }

public void setTimezone(String timezone) { this.timezone = timezone; }

}

基本連接管理器類,數(shù)據(jù)庫,這里只加載驅(qū)動程序一次,并為連接提供一個getter：

public class Database {

private String url;

private String username;

private String password;

public Database(String driver, String url, String username, String password) {

try {

Class.forName(driver);

} catch (ClassNotFoundException e) {

throw new RuntimeException("Driver class is missing in classpath", e);

}

this.url = url;

this.username = username;

this.password = password;

}

public Connection getConnection() {

return DriverManager.getConnection(url, username, password);

}

}

DAO類,AreaDAO,這里放置所有數(shù)據(jù)庫交互方法：

public class AreaDAO {

private Database database;

public AreaDAO(Database database) {

this.database = database;

}

public List list() throws SQLException {

Connection connection = null;

PreparedStatement statement = null;

ResultSet resultSet = null;

List areas = new ArrayList();

try {

connection = database.getConnection();

statement = connection.prepareStatement("SELECT location, timezone FROM userclient");

resultSet = statement.executeQuery();

while (resultSet.next()) {

Area area = new Area();

area.setLocation(resultSet.getString("location"));

area.setTimezone(resultSet.getString("timezone"));

areas.add(area);

}

} finally {

if (resultSet != null) try { resultSet.close(); } catch (SQLException logOrIgnore) {}

if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}

if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}

}

return areas;

}

}

最后,在servlet中初始化DAO一次并獲取HTTP方法中的列表：

public class AreaServlet extends HttpServlet {

private AreaDAO areaDAO;

public void init() throws ServletException {

String driver = "com.mysql.jdbc.Driver";

String url = "jdbc:mysql://localhost:3306/dbname";

String username = "user";

String password = "pass";

Database database = new Database(driver, url, username, password);

this.areaDAO = new AreaDAO(database);

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

try {

List areas = areaDAO.list();

request.setAttribute("areas", areas);

request.getRequestDispatcher("/WEB-INF/areas.jsp").forward(request, response);

} catch (SQLException e) {

throw new ServletException("Cannot retrieve areas", e);

}

}

}

將此servlet映射到web.xml中的/ areas區(qū)域的url-pattern上,以便您可以在http://example.com/contextname/areas之前調(diào)用它

/WEB-INF/areas.jsp看起來像這樣,假設(shè)您要顯示表中的區(qū)域：

${area.location}

${area.timezone}

也可以看看：

總結(jié)

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