关于网友提出的“ 调用DAO的问题，大家帮忙解决呀，”问题疑问，本网通过在网上对“ 调用DAO的问题，大家帮忙解决呀，”有关的相关答案进行了整理，供用户进行参考，详细问题解答如下：
问题： 调用DAO的问题，大家帮忙解决呀，
描述: UserDAO代码：
public interface UserDAO{
public Page getUserList(int start, int count)
throws UserDAOSysException;;
}
GenericUserDAO 代码：
public class GenericUserDAO implements UserDAO {
public Page getUserList(int start, int count) throws UserDAOSysException {
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
//connection = getDataSource().getConnection();
//String[] parameterValues = new String[] { locale.toString() };
//if (TRACE) {
// printSQLStatement(sqlStatements, XML_GET_CATEGORIES, parameterValues);
//}
//statement = buildSQLStatement(connection, sqlStatements, XML_GET_CATEGORIES, parameterValues);
DBQuery dbquey = new DBQuery();
resultSet = dbquey.executeQuery("select * from sysuser");
if (start >= 0 && resultSet.absolute(start + 1)) {
boolean hasNext = false;
List userList = new ArrayList();
do {
userList.add(new User(resultSet.getString(1).trim(),
resultSet.getString(2),
resultSet.getString(4),resultSet.getString(5)));
} while ((hasNext = resultSet.next()) && (--count > 0));
return new Page(userList, start, hasNext);
}
return Page.EMPTY_PAGE;
} catch (SQLException exception) {
throw new UserDAOSysException("SQLException: " + exception.getMessage());
} finally {
closeAll(connection, statement, resultSet);
}
}
protected static void closeAll(Connection connection, PreparedStatement statement, ResultSet resultSet) {
if (resultSet != null) {
try {
resultSet.close();
} catch (Exception exception) {}
}
if (statement != null) {
try {
statement.close();
} catch (Exception exception) {}
}
if (connection != null) {
try {
connection.close();
} catch (Exception exception) {}
}
return;
}
}
Page代码：
public class Page implements Serializable {
// XXX
/*
public static final Page EMPTY_PAGE =
new Page(Collections.EMPTY_LIST, 0, 0);
*/
public static final Page EMPTY_PAGE =
new Page(Collections.EMPTY_LIST, 0, false);
List objects;
int start;
// XXX
// int containingListSize;
boolean hasNext;
// XXX
/*
public Page(List l, int s, int cls) {
*/
public Page(List l, int s, boolean hasNext) {
objects = new ArrayList(l);
start = s;
// XXX
//containingListSize = cls;
this.hasNext = hasNext;
}
public List getList() { return objects; }
public boolean isNextPageAvailable() {
// XXX
/*
return (start + objects.size()) < containingListSize;
*/
return hasNext;
}
public boolean isPreviousPageAvailable() {
return start > 0;
}
public int getStartOfNextPage() { return start + objects.size(); }
public int getStartOfPreviousPage() {
return Math.max(start-objects.size(), 0);
}
public int getSize() { return objects.size(); }
}
UserDAOFactory 代码：
public class UserDAOFactory {
public static UserDAO getUserDAO() {
UserDAO userDao = null;
//依据系统配置的信息，产生一个实现类
String driverClasses = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
StringTokenizer st = new StringTokenizer(driverClasses);
while (st.hasMoreElements()) {
String driverClassName = st.nextToken().trim();
try {
userDao = (UserDAO) Class.forName(driverClasses).newInstance();
} catch (Exception ne) {
}
}
return userDao;
}
}
User 代码：
public class User implements java.io.Serializable {
private String id;
private String name;
private String email;
private String LogName;
public User(String id, String name, String email, String LogName) {
this.id = id;
this.name = name;
this.email = email;
this.LogName = LogName;
}
/**
* Class constructor with no arguments, used by the web tier.
*/
public User() {}
public String getId() { return id; }
public String getName() { return name; }
public String getEmail() { return email; }
public String getLogName() { return LogName; }
public String toString() {
return "{ id=" + id + "; name=" + name + "; email="
+ email + "; LogName="
+ LogName + "}";
}
}
beanUser 代码：
public class beanUser {
protected UserDAO dao;
public void beanUser() {
try {
//使用工程模式，产生DAO
dao = UserDAOFactory.getUserDAO();
} catch (Exception e) {
}
}
public Page getUserList(int start, int count) {
Page page=null;
try {
//调用DAO,实现业务逻辑
System.out.println("dao====="+dao);
dao = UserDAOFactory.getUserDAO();
page=dao.getUserList(start,count);
}
catch (UserDAOSysException se) {
}
return page;
}
}
我在jsp页面中这样调用的:
解决方案1: 最好把GenericUserDAO的构造方法定义成protected
解决方案2: UserDAOFactory 代码：
public class UserDAOFactory {
public static UserDAO getUserDAO() {
UserDAO userDao = null;
String driverClasses = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
try {
Class.forName(driverClasses);
userDao = new GenericUserDAO();
} catch (ClassNotFoundException cnfe) {
}
}
return userDao;
}
}
以上介绍了“ 调用DAO的问题，大家帮忙解决呀，”的问题解答，希望对有需要的网友有所帮助。
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