通用分页（上）
通用分页
- 通用分页核心思路
- 通用分页案例
- 总结
通用分页核心思路
通用分页核心思路：将上一次查询请求再发一次，只不过页码变了
通用分页案例
1、先将需要的导入的jar包放到web-inf下面的lib文件中
config.properties配置文件：
#oracle9i
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@localhost:1521:orcl
#user=scott
#pwd=tiger
#sql2005
#driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
#url=jdbc:sqlserver://localhost:1433;DatabaseName=test1
#user=sa
#pwd=123
#sql2000
#driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
#url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
#user=sa
#pwd=888888
#mysql
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/t243?useUnicode=true&characterEncoding=UTF-8
user=root
pwd=123
这里我用的是最后一个mysql的，用需要用别的数据库的可以将前面的#删除，就可以使用了。
接下来就可以解析配置文件的内容，链接数据库：
package com.zhangsiwen.test.util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* 提供了一组获得或关闭数据库对象的方法
*
*/
public class DBAccess {
private static String driver;
private static String url;
private static String user;
private static String password;
static {// 静态块执行一次，加载 驱动一次
try {
InputStream is = DBAccess.class
.getResourceAsStream("config.properties");
Properties properties = new Properties();
properties.load(is);
driver = properties.getProperty("driver");
url = properties.getProperty("url");
user = properties.getProperty("user");
password = properties.getProperty("pwd");
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
/**
* 获得数据连接对象
*
* @return
*/
public static Connection getConnection() {
try {
Connection conn = DriverManager.getConnection(url, user, password);
return conn;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
public static void close(ResultSet rs) {
if (null != rs) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}
public static void close(Statement stmt) {
if (null != stmt) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}
public static void close(Connection conn) {
if (null != conn) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}
public static void close(Connection conn, Statement stmt, ResultSet rs) {
close(rs);
close(stmt);
close(conn);
}
public static boolean isOracle() {
return "oracle.jdbc.driver.OracleDriver".equals(driver);
}
public static boolean isSQLServer() {
return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
}
public static boolean isMysql() {
return "com.mysql.jdbc.Driver".equals(driver);
}
}
连接之后可以写一个main方法用来测试：
public static void main(String[] args) {
Connection conn = DBAccess.getConnection();
DBAccess.close(conn);
System.out.println("isOracle：" + isOracle());
System.out.println("isSQLServer：" + isSQLServer());
System.out.println("isMysql：" + isMysql());
System.out.println("数据库连接(关闭)成功");
}
运行结果：
处理中文乱码的工具类
package com.zhangsiwen.test.util;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 中文乱码处理
*
*/
public class EncodingFiter implements Filter {
private String encoding = "UTF-8";// 默认字符集
public EncodingFiter() {
super();
}
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
// 中文处理必须放到 chain.doFilter(request, response)方法前面
res.setContentType("text/html;charset=" + this.encoding);
if (req.getMethod().equalsIgnoreCase("post")) {
req.setCharacterEncoding(this.encoding);
} else {
Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
Set set = map.keySet();// 取出所有参数名
Iterator it = set.iterator();
while (it.hasNext()) {
String name = (String) it.next();
String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
for (int i = 0; i < values.length; i++) {
values[i] = new String(values[i].getBytes("ISO-8859-1"),
this.encoding);
}
}
}
chain.doFilter(request, response);
}
public void init(FilterConfig filterConfig) throws ServletException {
String s = filterConfig.getInitParameter("encoding");// 读取web.xml文件中配置的字符集
if (null != s && !s.trim().equals("")) {
this.encoding = s.trim();
}
}
}
判断字符串是否为空
package com.zhangsiwen.test.util;
public class StringUtils {
// 私有的构造方法，保护此类不能在外部实例化
private StringUtils() {
}
/**
* 如果字符串等于null或去空格后等于""，则返回true，否则返回false
*
* @param s
* @return
*/
public static boolean isBlank(String s) {
boolean b = false;
if (null == s || s.trim().equals("")) {
b = true;
}
return b;
}
/**
* 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
*
* @param s
* @return
*/
public static boolean isNotBlank(String s) {
return !isBlank(s);
}
}
然后就是我们的实体类
package com.zhangsiwen.test.entity;
import java.io.Serializable;
import com.zhangsiwen.test.util.PinYinUtil;
public class Student implements Serializable{
private static final long serialVersionUID = 1L;
private int sid;
private String sname;
private String sname_pinyin;
private int age;
private String remark;
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
this.sname_pinyin=PinYinUtil.toPinyin(this.sname);
}
public String getSname_pinyin() {
return sname_pinyin;
}
public void setSname_pinyin(String sname_pinyin) {
this.sname_pinyin = sname_pinyin;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getRemark() {
return remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
public Student() {
super();
}
public Student(int sid, String sname, String sname_pinyin, int age, String remark) {
super();
this.sid = sid;
this.sname = sname;
this.sname_pinyin = sname_pinyin;
this.age = age;
this.remark = remark;
}
@Override
public String toString() {
return "Student [sid=" + sid + ", sname=" + sname + ", sname_pinyin=" + sname_pinyin + ", age=" + age
+ ", remark=" + remark + "]";
}
}
通用方法的实体类
package com.zhangsiwen.test.util;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
public class PageBean {
private int page=1;//页码
private int rows=10;//页的大小
private int total=0;//总记录数 从数据库中进行统计的
private boolean pagination =true;//是否分页 默认分页
private String url;//请求路径
private Map ParameterMap=new HashMap();
//专门写一个方法，用来做pageBean的初始化
public void setRequest(HttpServletRequest request) {
//page rows pagination 公开参数 只能做分页
//从界面获取到分页的参数
String page=request.getParameter("page");
String rows=request.getParameter("rows");
String pagination=request.getParameter("pagination");
//给参数赋值
this.setPage(page);
this.setRows(rows);
this.setPagination(pagination);
//获取请求路径
this.url=request.getContextPath()+request.getServletPath();
//获取界面传递的参数
this.ParameterMap=request.getParameterMap();
}
//上一页
public int getPreviousPage() {
int previousPage=this.page-1;
if(0==previousPage) {
previousPage=1;
}
return previousPage;
}
//下一页
public int getNextPage() {
int nextPage=this.page+1;
if(nextPage>getMaxPage()) {
nextPage=getMaxPage();
}
return nextPage;
}
public int getPage() {
return page;
}
public void setPage(int page) {
this.page = page;
}
public void setPage(String page) {
if(null!=page&&!"".equals(page.trim())) {
this.page=Integer.parseInt(page);
}
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public Map getParameterMap() {
return ParameterMap;
}
public void setParameterMap(Map parameterMap) {
ParameterMap = parameterMap;
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
this.rows = rows;
}
public void setRows(String rows) {
if(null!=rows&&!"".equals(rows.trim())) {
this.rows=Integer.parseInt(rows);
}
}
public int getTotal() {
return total;
}
public void setTotal(int total) {
this.total = total;
}
public boolean isPagination() {
return pagination;
}
public void setPagination(boolean pagination) {
this.pagination = pagination;
}
public void setPagination(String pagination) {
if("false".equals(pagination)) {
this.pagination=Boolean.parseBoolean(pagination);
}
}
public PageBean() {
super();
}
public PageBean(int page, int rows, int total, boolean pagination) {
super();
this.page = page;
this.rows = rows;
this.total = total;
this.pagination = pagination;
}
/**
* 获得起始记录的下标
* @return
*/
public int getStartsIndex() {
return (this.page-1)*this.rows;
}
/**
* 获取最大页数
* @return
*/
public int getMaxPage() {
int maxPage=this.total/this.rows;
if(0!=this.total%this.rows) {
maxPage=maxPage+1;
}
return maxPage;
}
@Override
public String toString() {
return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
}
}
写一个dao类
package com.zhangsiwen.test.dao;
import java.io.Serializable;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.sun.javafx.css.Style;
import com.zhangsiwen.test.entity.Student;
import com.zhangsiwen.test.util.DBAccess;
import com.zhangsiwen.test.util.PageBean;
import com.zhangsiwen.test.util.StringUtils;
public class StudentDao extends BaseDao implements Serializable{
private static final long serialVersionUID = 1L;
/**
* 增加方法
* @param student
*/
public void add(Student student) {
Connection con=null;
PreparedStatement ps=null;
ResultSet rs=null;
String sql="insert into t_student (sname,sname_pinyin,age,remark) value(?,?,?,?)";
try {
con=DBAccess.getConnection();
ps=con.prepareStatement(sql);
ps.setString(1,student.getSname());
ps.setString(2,student.getSname_pinyin());
ps.setInt(3,student.getAge());
ps.setString(4,student.getRemark());
ps.executeUpdate();
} catch (Exception e) {
throw new RuntimeException(e);
}finally {
DBAccess.close(con,ps, rs);
}
}
/**
* 查询所有 模糊查询
* @param student
* @return
*/
public List find(Student student){
List stuList=new ArrayList();
Connection con=null;
PreparedStatement ps=null;
ResultSet rs=null;
String sql="select * from t_student where 1=1";
if(StringUtils.isNotBlank(student.getSname())){
//sql+=" and sname like '%"+student.getSname() +"%' ";
sql+=" and (sname like '%"+student.getSname() +"%' or sname_pinyin like '%"+student.getSname()+"%' )";
}
try {
con=DBAccess.getConnection();
ps=con.prepareStatement(sql);
rs=ps.executeQuery();
Student stu=null;
while(rs.next()) {
stu=new Student();
stu.setSid(rs.getInt("sid"));
stu.setSname(rs.getString("sname"));
stu.setSname_pinyin(rs.getString("sname_pinyin"));
stu.setAge(rs.getInt("age"));
stu.setRemark(rs.getString("remark"));
stuList.add(stu);
}
} catch (Exception e) {
throw new RuntimeException(e);
}finally {
DBAccess.close(con,ps, rs);
}
return stuList;
}
public List find(Student student,PageBean pageBean){
String sql="select * from t_student where 1=1 ";
if(StringUtils.isNotBlank(student.getSname())){
//sql+=" and sname like '%"+student.getSname() +"%' ";
sql+=" and sname like '%"+student.getSname()+"%' or sname_pinyin like '%"+student.getSname()+"%'";
}
return this.executeQuery(sql, pageBean, new Callback() {
@Override
public List foreach(ResultSet rs) throws SQLException {
List stuList=new ArrayList();
Student stu=null;
while(rs.next()) {
stu=new Student();
stu.setSid(rs.getInt("sid"));
stu.setSname(rs.getString("sname"));
stu.setSname_pinyin(rs.getString("sname_pinyin"));
stu.setAge(rs.getInt("age"));
stu.setRemark(rs.getString("remark"));
stuList.add(stu);
}
return stuList;
}
});
}
/**
* 专门写一个方法用来拼接查询语句的 统计满足条件的总行数
* @param sql 满足条件的sql
* @return
*/
public String getCountSql(String sql) {
return "select count(*) from ("+sql+")t1 ";
}
/**
* 专门写一个方法用来存储拼接分页的sql
* @param sql 查询指定页码并满足条件的sql语句
* @param pageBean 助手类
* @return
*/
public String getPageSql(String sql,PageBean pageBean) {
return sql+"limit "+pageBean.getStartsIndex() +","+pageBean.getRows()+"";
}
}
写一个junit单元测试测试一下
package com.zhangsiwen.test.dao;
import static org.junit.Assert.*;
import java.util.List;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.zhangsiwen.test.entity.Student;
import com.zhangsiwen.test.util.PageBean;
public class StudentDaoTest {
private StudentDao stuDao=new StudentDao();
private Student stu=null;
@Before
public void setUp() throws Exception {
System.out.println("执行测试方法之前调用，做初始化");
stu =new Student();
}
@After
public void tearDown() throws Exception {
System.out.println("执行测试方法之后调用，要来做销毁");
}
@Test
public void testAdd() {
System.out.println("专门用来测试add的方法");
for(int i=0;i<50;i++) {
stu.setSname("张明明"+i);
stu.setAge(18+i);
stu.setRemark("abcd"+i);
stuDao.add(stu);
}
}
@Test
public void testFind() {
System.out.println("专门用来测试find的方法");
stu.setSname("王");
List student=stuDao.find(stu);
for (Student s : student) {
System.out.println(s);
}
}
@Test
public void testFind2() {
PageBean pageBean =new PageBean();
pageBean.setPage(1);
pageBean.setRows(10);
pageBean.setPagination(true);
stu.setSname("张");
List student=stuDao.find(stu,pageBean);
System.out.println(pageBean);
for (Student s : student) {
System.out.println(s);
}
}
}
选择运行find2，运行结果
总结
这是通用分页的上半部分，下半部分将在下一篇博客，敬请期待！