import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.Statement;

import java.util.Vector;

/**

* Pager, 基于 JDBC 2.0 滾動(dòng)機(jī)制的分頁(yè)程序, 在 MySQL, SQLServer, Access, Oracle 下測(cè)試通過(guò).

* @author 劉長(zhǎng)炯

* @version 1.0 2004-8-12

*/

public class Pager {

/** Used database connection */

Connection conn = null;

public Pager() {

}

/**

* 分頁(yè)功能, 返回當(dāng)頁(yè)的數(shù)據(jù)(JDBC 2.0 實(shí)現(xiàn)).

* 

* @param currentPage

* 當(dāng)前頁(yè)面數(shù)(取值范圍: 從 1 開(kāi)始有效, 0 自動(dòng)改為 1)

* @param pageCount

* 每頁(yè)顯示記錄數(shù)

* 

* @return a Vector - 數(shù)據(jù)列表

*/

public Vector pageData(int currentPage, int pageCount) {

Vector results = new Vector();

String tableName = "table_name";// 要處理的表格名

ResultSet rs = null;

String sql = "SELECT * FROM " + tableName;

Statement stmt = null;

try {

// TODO: open connection

// 生成可滾動(dòng)的結(jié)果集表達(dá)式

stmt = conn.createStatement(ResultSet.

TYPE_SCROLL_SENSITIVE,

ResultSet.CONCUR_READ_ONLY);

rs = stmt.executeQuery(sql);

int count = recordCount(); // 總記錄數(shù)

int totalPage = (int) Math.ceil(1.0 * count / pageCount); // 總頁(yè)面數(shù)

if (currentPage <= 0) {

currentPage = 1;

}

// 超出頁(yè)碼范圍, 不返回?cái)?shù)據(jù)

if (currentPage > totalPage) {

currentPage = totalPage;

return results;

}

if ((currentPage - 1) * pageCount > 0) {

// 移動(dòng)結(jié)果集數(shù)據(jù)到當(dāng)前頁(yè)

rs.absolute((currentPage - 1) * pageCount);

}

// rs.absolute(0); 在 ODBC 下會(huì)導(dǎo)致如下異常:java.sql.SQLException: Cursor

// position (0) is invalid

int i = 0; // Readed pages

while (rs.next() && i < pageCount) {

i++;

// TODO: Read each row and process to value object

ValueObject bean = new ValueObject();

// TODO: Read value to value object

result.add(bean);

}

} catch (Exception exception) {

System.out.println("Occur a error in " + getClass()

+ ".pageData() : " + exception.getMessage());

// exception.printStackTrace();

} finally {

closeJDBCResource(stmt);

closeJDBCResource(rs);

closeJDBCResource(conn);

}

return results;

}

/**

* 返回當(dāng)前數(shù)據(jù)庫(kù)中記錄的總數(shù).

* 

* @return int 記錄總數(shù)

*/

public int recordCount() {

int allCount = -1;

String tableName = "table_name";// 要處理的表格名

String sql = "SELECT COUNT(*) FROM " + tableName;

ResultSet rs = null;

Statement stmt = null;

try {

// TODO: open connection

stmt = conn.createStatement();

rs = stmt.executeQuery(sql);

if (rs.next()) {

allCount = rs.getInt(1);

}

} catch (Exception exception) {

System.out

.println("Occur a error in " + getClass()

+ ".recordCount() : " + exception.getMessage());

} finally {

closeJDBCResource(stmt);

closeJDBCResource(rs);

closeJDBCResource(conn);

}

return allCount;

}

/**

* Close a jdbc resource, such as ResultSet, Statement, Connection.... All

* these objects must have a method signature is void close().

* 

* @param resource -

* jdbc resouce to close

*/

public static void closeJDBCResource(Object resource) {

try {

Class clazz = resource.getClass();

java.lang.reflect.Method method = clazz.getMethod("close", null);

method.invoke(resource, null);

} catch (Exception e) {

e.printStackTrace();

}

}

/**

* Test page.

* @param args

*/

public static void main(String[] args) {

// 分頁(yè), 讀取第一頁(yè)數(shù)據(jù), 共讀取5個(gè)記錄

Vector data = new Pager().pageData(1, 5);

// TODO: process value object, 更改類名

for(int i = 0; results != null && i < data.size(); i++) {

ValueObject bean = (ValueObject)data.get(i);

}

}

}