javaee分页（下）

package com.xuyahui.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.cj.jdbc.Driver".equals(driver);
  }
  public static void main(String[] args) {
    Connection conn = DBAccess.getConnection();
    System.out.println(conn);
    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");
  }
}

package com.xuyahui.entity;
/**
 * @author 小徐
 * @com.xuyahui.entity
 * @Book(说明):书(实体类)
 */
public class Book {
  private int bid;
  private String bname;
  private float price;
  @Override
  public String toString() {
    return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
  }
  public int getBid() {
    return bid;
  }
  public void setBid(int bid) {
    this.bid = bid;
  }
  public String getBname() {
    return bname;
  }
  public void setBname(String bname) {
    this.bname = bname;
  }
  public float getPrice() {
    return price;
  }
  public void setPrice(float price) {
    this.price = price;
  }
  public Book(int bid, String bname, float price) {
    super();
    this.bid = bid;
    this.bname = bname;
    this.price = price;
  }
  public Book() {
    super();
  }
}

package com.xuyahui.Dao;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.xuyahui.entity.Book;
import com.xuyahui.util.DBAccess;
import com.xuyahui.util.PageBean;
public class BaseDao<T> {
  /**
   * 带分类的模糊查询
   * @param sql
   * @param clz
   * @param pageBean
   * @return
   * @throws Exception
   */
  public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws Exception{
    List<T> list = new ArrayList<T>();
    Connection conn = null;
    PreparedStatement pst = null;
    ResultSet rs = null;
    if(pageBean != null && pageBean.isPagination()) {
      String countSQL = getCountSQL(sql);
      conn = DBAccess.getConnection();
      pst = conn.prepareStatement(countSQL);
      rs = pst.executeQuery();
      if(rs.next()) {
        pageBean.setTotal(rs.getObject("n").toString());
      }
      String pageSQL = getPageSQL(sql,pageBean);
      conn = DBAccess.getConnection();
      pst = conn.prepareStatement(pageSQL);
      rs = pst.executeQuery();
    }else {
      conn = DBAccess.getConnection();
      pst = conn.prepareStatement(sql);
      rs = pst.executeQuery();
    }
    while(rs.next()) {
      T t = (T) clz.newInstance();//反射
//      拿到clz对应的所有属性对象
      Field[] fields = clz.getDeclaredFields();//拿到属性
      for (Field f : fields) {
        f.setAccessible(true);
        f.set(t, rs.getObject(f.getName()));//保存属性
      }
      list.add(t);
    }
    return list;  //最后循坏遍历
  }
/**
 *  拼接处最终展示数据的sql
 * @param sql  原生sql
 * @return
 */
  private String getCountSQL(String sql) {
    return "select count(1) as n from ("+sql+") t";
  }
/**
 * 拼接处查询符合条件的总记录数SQL
 * @param sql
 * @param pageBean
 * @return
 */
  private String getPageSQL(String sql, PageBean pageBean) {
    return  sql+" limit "+pageBean.getStartIndex()+","+pageBean.getRows();
  }
}

package com.xuyahui.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);
  }
}

package com.xuyahui.util;
import java.io.IOException;
import java.util.Map;
import java.util.Set;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
/**
 * @author 小徐
 * @com.xuyahui.entity
 * @PageTag(说明):标签帮助类
 */
public class PageTag extends BodyTagSupport {
    private PageBean pageBean;
    public PageBean getPageBean() {
        return pageBean;
    }
    public void setPageBean(PageBean pageBean) {
        this.pageBean = pageBean;
    }
    @Override
    public int doStartTag() throws JspException {
        JspWriter out = pageContext.getOut();
        try {
            out.print(toHTML());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return SKIP_BODY;
    }
    private String toHTML() {
        StringBuilder sb = new StringBuilder();
//        这里拼接的是一个上一次发送的请求以及携带的参数，唯一改变的就是页码
        sb.append("<form id='pageBeanForm' action='"+pageBean.getUrl()+"' method='post'>");
//        sb.append("<input type='hidden' name='methodName' value='list'>");
        sb.append("<input type='hidden' name='page'>");
//        重要设置拼接操作，将上一次请求参数携带到下一次
        Map<String, String[]> paMap = pageBean.getPageMap();
        if(paMap !=null && paMap.size()>0){
            Set<Map.Entry<String, String[]>> entrySet = paMap.entrySet();
            for (Map.Entry<String, String[]> entry : entrySet) {
                for (String val : entry.getValue()) {
                    if(!"page".equals(entry.getKey())){
                        sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+val+"'>");
                    }
                }
            }
        }
        sb.append("</form>");
        int page = pageBean.getPage();
        int max = pageBean.getMaxPage();
        int before = page > 4 ? 4 : page-1;
        int after = 10 - 1 - before;
        after = page+after > max ? max-page : after;
//        disabled
        boolean startFlag = page == 1;
        boolean endFlag = max == page;
//        拼接分页条
        sb.append("<ul class='pagination'>");
        sb.append("<li class='page-item "+(startFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage(1)'>首页</a></li>");
        sb.append("<li class='page-item "+(startFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.getPrevPage()+")'>&lt;</a></li>");
//        代表了当前页的前4页
        for (int i = before; i > 0 ; i--) {
            sb.append("<li class='page-item'><a class='page-link' href='javascript:gotoPage("+(page-i)+")'>"+(page-i)+"</a></li>");
        }
        sb.append("<li class='page-item active'><a class='page-link' href='javascript:gotoPage("+pageBean.getPage()+")'>"+pageBean.getPage()+"</a></li>");
//        代表了当前页的后5页
        for (int i = 1; i <= after; i++) {
            sb.append("<li class='page-item'><a class='page-link' href='javascript:gotoPage("+(page+i)+")'>"+(page+i)+"</a></li>");
        }
        sb.append("<li class='page-item "+(endFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.getNextPage()+")'>&gt;</a></li>");
        sb.append("<li class='page-item "+(endFlag ? "disabled" : "")+"'><a class='page-link' href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a></li>");
        sb.append("<li class='page-item go-input'><b>到第</b><input class='page-link' type='text' id='skipPage' name='' /><b>页</b></li>");
        sb.append("<li class='page-item go'><a class='page-link' href='javascript:skipPage()'>确定</a></li>");
        sb.append("<li class='page-item'><b>共"+pageBean.getTotal()+"条</b></li>");
        sb.append("</ul>");
//        拼接分页的js代码
        sb.append("<script type='text/javascript'>");
        sb.append("function gotoPage(page) {");
        sb.append("document.getElementById('pageBeanForm').page.value = page;");
        sb.append("document.getElementById('pageBeanForm').submit();");
        sb.append("}");
        sb.append("function skipPage() {");
        sb.append("var page = document.getElementById('skipPage').value;");
        sb.append("if (!page || isNaN(page) || parseInt(page) < 1 || parseInt(page) > "+max+") {");
        sb.append("alert('请输入1~N的数字');");
        sb.append("return;");
        sb.append("}");
        sb.append("gotoPage(page);");
        sb.append("}");
        sb.append("</script>");
        return sb.toString();
    }
}

package com.xuyahui.util;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
/**
 * @author 小徐
 * @com.xuyahui.utils
 * @PageBean(说明):分页工具类
 */
public class PageBean {
  private int page = 1;// 页码
  private int rows = 10;// 页大小
  private int total = 0;// 总记录数
  private boolean pagination = true;// 是否分页
  private String url;
  private Map<String, String[]> pageMap;
  public void setRequest(HttpServletRequest req) {
    // 初次进入jsp页面传递过来的当前页
    this.setPage(req.getParameter("page"));
    // 初次进入jsp页面传递过来的页大小
    this.setRows(req.getParameter("rows"));
    // 初次进入jsp页面传递过来是否分页
    this.setPagination(req.getParameter("pagination"));
    // 保留上一次的查询请求
    this.setUrl(req.getRequestURL().toString());
    // 保留上一次的查询条件
    this.setPageMap(req.getParameterMap());
  }
  public void setPagination(String pagination) {
    // 只有填写了false字符串，才代表不分页
    this.setPagination(!"false".equals(pagination));
  }
  public void setRows(String rows) {
    if (StringUtils.isNotBlank(rows))
    this.setRows(Integer.valueOf(rows));
  }
  public void setPage(String page) {
    if (StringUtils.isNotBlank(page))
      this.setPage(Integer.valueOf(page));
  }
  // 上一页
  public int getPrevPage() {
    return this.page > 1 ? this.page - 1 : this.page;
  }
  // 下一页
  public int getNextPage() {
    return this.page < this.getMaxPage() ? this.page + 1 : this.page;
  }
  // 最大页
  public int getMaxPage() {
    return this.total % this.rows == 0 ? this.total / this.rows : (this.total / this.rows) + 1;
  }
  public String getUrl() {
    return url;
  }
  public void setUrl(String url) {
    this.url = url;
  }
  public Map<String, String[]> getPageMap() {
    return pageMap;
  }
  public void setPageMap(Map<String, String[]> pageMap) {
    this.pageMap = pageMap;
  }
  public PageBean() {
    super();
  }
  public int getPage() {
    return page;
  }
  public void setPage(int page) {
    this.page = page;
  }
  public int getRows() {
    return rows;
  }
  public void setRows(int rows) {
    this.rows = rows;
  }
  public int getTotal() {
    return total;
  }
  public void setTotal(int total) {
    this.total = total;
  }
  public void setTotal(String total) {
    this.total = Integer.parseInt(total);
  }
  public boolean isPagination() {
    return pagination;
  }
  public void setPagination(boolean pagination) {
    this.pagination = pagination;
  }
  /**
   * 获得起始记录的下标
   * @return 
   */
  public int getStartIndex() {
    return (this.page - 1) * this.rows;
  }
  @Override
  public String toString() {
    return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
  }
}

<%@ page language="java" contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"%>
  <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html >
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link
  href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.css"
  rel="stylesheet">
<script
  src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.js"></script>
<title>书籍列表</title>
<style type="text/css">
.page-item input {
  padding: 0;
  width: 40px;
  height: 100%;
  text-align: center;
  margin: 0 6px;
}
.page-item input, .page-item b {
  line-height: 38px;
  float: left;
  font-weight: 400;
}
.page-item.go-input {
  margin: 0 10px;
}
</style>
</head>
<body>
  <form class="form-inline"
    action="${pageContext.request.contextPath }/book.action" method="post">
    <div class="form-group mb-2">
      <input type="text" class="form-control-plaintext" name="bname"
        placeholder="请输入书籍名称">
    </div>
    <button type="submit" class="btn btn-primary mb-2">查询</button>
  </form>
  <table class="table table-striped bg-success">
    <thead>
      <tr>
        <th scope="col">书籍ID</th>
        <th scope="col">书籍名</th>
        <th scope="col">价格</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td>1</td>
        <td>圣墟第1章</td>
        <td>1</td>
      </tr>
      <tr>
        <td>1</td>
        <td>圣墟第1章</td>
        <td>1</td>
      </tr>
    </tbody>
  </table>
  <form action="" id="pageBeanForm" method="post">
    <input type="hidden" name="page">
  </form>zzz
  <ul class="pagination justify-content-center">
    <li class="page-item"><a class="page-link"
      href='javascript:gotoPage(1)'>首页</a></li>
    <li class="page-item"><a class="page-link"
      href='javascript:gotoPage(1)'>&lt;</a></li>
    <li class="page-item"><a class="page-link" href="#">1</a></li>
    <li class="page-item"><a class="page-link" href="#">2</a></li>
    <li class="page-item active"><a class="page-link" href="#">3</a></li>
    <li class="page-item disabled"><a class="page-link" href="#">&gt;</a></li>
    <li class="page-item disabled"><a class="page-link" href="#">尾页</a></li>
    <li class="page-item go-input"><b>到第</b><input class="page-link"
      type="text" id="skipPage" name="" /><b>页</b></li>
    <li class="page-item go"><a class="page-link"
      href="javascript:skipPage()">确定</a></li>
    <li class="page-item"><b>共666条</b></li>
  </ul>
  <script type='text/javascript'>
    function gotoPage(page) {
      document.getElementById('pageBeanForm').page.value = page;
      document.getElementById('pageBeanForm').submit();
    }
    function skipPage() {
      var page = document.getElementById('skipPage').value;
      if (!page || isNaN(page) || parseInt(page) < 1
          || parseInt(page) > 1122) {
        alert('请输入1~N的数字');
        return;
      }
      gotoPage(page);
    }
  </script>
</body>
</html>