Java Web——分页技术

 1 /**
 2      * 查询雇员（根据条件组合查询-数据库分页）
 3      * @param emp
 4      * @param pageSize 每页显示条数
 5      * @param pageNum  当前页码
 6      * @return
 7      */
 8     public List<Emp> getEmp(Emp emp, int pageSize, int pageNum) {
 9         try {
10             
11             String sql = "select * from ( select e.empno,e.ename,e.job,e.mgr,e.hiredate,e.sal,e.comm,e.deptno,d.dname,d.loc,m.ename mgrname,rownum rn "
12                     + " from emp e,dept d,emp m "
13                     + " where e.mgr = m.empno(+) and e.deptno = d.deptno ";
14             
15             
16             //绑定查询条件---start---------------------------------------------------
17             //雇员编号
18             int empno= emp.getEmpno();
19             if(empno > 0)
20             {
21                 sql += " and e.empno like ‘%" + empno +"%‘ ";
22             }
23             //雇员姓名
24             String ename = emp.getEname();
25             if(ename != null && !"".equals(ename))
26             {
27                 sql += " and e.ename like ‘%" + ename +"%‘ ";//模糊查询
28             }
29             //职位
30             String job = emp.getJob();
31             if(job != null && !"".equals(job))
32             {
33                 sql += " and e.job = ‘" + job +"‘ ";
34             }
35             //部门编号
36             int deptno = emp.getDept().getDeptno();
37             if(deptno > 0)
38             {
39                 sql += " and e.deptno = " + deptno;
40             }
41             //绑定查询条件---end---------------------------------------------------
42             
43             sql += " and rownum <= "+ (pageSize * pageNum) +"   ) where rn >= " + ((pageNum-1) * pageSize +1);
44             
45             System.out.println(sql);
46             
47             stat =  conn.prepareStatement(sql);
48             
49             rs = stat.executeQuery();
50             
51             List<Emp> empList = new ArrayList<Emp>();
52             
53             while(rs.next())
54             {
55                 Emp temp = new Emp();
56                 temp.setEmpno(rs.getInt("empno"));
57                 temp.setEname(rs.getString("ename"));
58                 temp.setJob(rs.getString("job"));
59                 
60                 //上级主管(复合属性)
61                 Emp mgr = new Emp();
62                 mgr.setEmpno(rs.getInt("mgr"));
63                 mgr.setEname(rs.getString("mgrname"));
64                 //......
65                 temp.setMgr(mgr);
66                 
67                 temp.setHiredate(rs.getDate("hiredate"));
68                 temp.setSalary(rs.getDouble("sal"));
69                 temp.setComm(rs.getDouble("comm"));
70                 
71                 //部门(复合属性)
72                 Dept dept = new Dept();
73                 dept.setDeptno(rs.getInt("deptno"));
74                 dept.setDname(rs.getString("dname"));
75                 dept.setLocation(rs.getString("loc"));
76                 temp.setDept(dept);
77                 
78                 empList.add(temp);
79             }
80             return empList;
81             
82         } catch (SQLException e) {
83             e.printStackTrace();
84         }
85         return null;
86     }
87 
88 }

 1 package Util;
 2 
 3 import java.util.List;
 4 
 5 import model.User;
 6 
 7 public class PageUtil {
 8     //总页数
 9     private int pageCount;
10     //总行数
11     private int rowCount;
12     //当前页数，默认情况下为1
13     private int pageNum = 1;
14     //每页条数,默认情况下为5
15     private int pageSize = 5;
16     //开始索引(重要)
17     private int beginIndex;
18     //结束索引(重要)
19     private int endIndex;
20     
21     //构造函数
22     public PageUtil(List<User> user){
23         //为总行数赋值
24         this.rowCount = user.size();
25         //算出总页数，并赋值
26         if(this.rowCount%this.pageSize==0){
27             this.pageCount = this.rowCount/this.pageSize;
28         }else {
29             this.pageCount = this.rowCount/this.pageSize+1;
30         }
31         setPageNum(this.pageNum);
32     }
33 
34     public int getPageCount() {
35         return pageCount;
36     }
37 
38     public void setPageCount(int pageCount) {
39         this.pageCount = pageCount;
40     }
41 
42     public int getRowCount() {
43         return rowCount;
44     }
45 
46     public void setRowCount(int rowCount) {
47         this.rowCount = rowCount;
48     }
49 
50     public int getPageNum() {
51         return pageNum;
52     }
53 
54     public void setPageNum(int pageNum) {
55         this.pageNum = pageNum;
56         //计算开始索引
57         this.beginIndex = (this.pageNum-1)*this.pageSize;
58         //计算结束索引
59         this.endIndex = this.pageNum*this.pageSize;
60         if(this.endIndex>this.rowCount){
61             this.endIndex = this.rowCount;
62         }
63     }
64 
65     public int getPageSize() {
66         return pageSize;
67     }
68 
69     public void setPageSize(int pageSize) {
70         this.pageSize = pageSize;
71     }
72 
73     public int getBeginIndex() {
74         return beginIndex;
75     }
76 
77     public void setBeginIndex(int beginIndex) {
78         this.beginIndex = beginIndex;
79     }
80 
81     public int getEndIndex() {
82         return endIndex;
83     }
84 
85     public void setEndIndex(int endIndex) {
86         this.endIndex = endIndex;
87     }
88     
89     
90 }

 1 String pageNum = request.getParameter("pageNum");
 2         HttpSession session = request.getSession();
 3         //当不指定具体是哪一页时
 4         if(pageNum==null||"".equals(pageNum)){
 5             //1.取得参数
 6             String username = request.getParameter("username");
 7             String sex = request.getParameter("sex");
 8             String cert_type = request.getParameter("cert_type");
 9             String cert = request.getParameter("cert");
10             String user_type = request.getParameter("user_type");
11             System.out.println("servlet:"+username);
12             //2.封装进对象
13             User user = new User();
14             user.setUsername(username);
15             user.setSex(sex);
16               //如果对象需要转化为int，那么为了防止使用Interger.valueof()方法时出现空指针情况，必须先进行判断是否为空
17             if(cert_type != null && !"".equals(cert_type))
18             {
19                 user.setCert_type(Integer.valueOf(cert_type));
20             }
21             user.setCert(cert);
22             if(user_type != null && !"".equals(user_type))
23             {
24                 user.setUser_type(Integer.valueOf(user_type));
25             }
26             
27             //3.调用服务层方法取得结果集
28             List<User> users = SelectUserService.Instance().getUser(user);
29             //4.对结果集进行分页操作
30             PageUtil pu = new PageUtil(users);
31             List<User> selectUsers = users.subList(pu.getBeginIndex(), pu.getEndIndex());
32               //结果集存入session中，可以让下次指定页数分页时不用再重新用服务层
33             session.setAttribute("users", users);
34               //分页好的结果存入session中
35             session.setAttribute("selectUsers", selectUsers);
36               //分页信息存入session
37             session.setAttribute("pu", pu);

 1 else {
 2             //指定某一页时，调用分页工具类修改页面
 3             PageUtil pu = (PageUtil) session.getAttribute("pu");
 4             List<User> users = (List<User>) session.getAttribute("users");
 5             pu.setPageNum(Integer.valueOf(pageNum));
 6             List<User> selectUsers = users.subList(pu.getBeginIndex(), pu.getEndIndex());
 7             session.setAttribute("selectUsers", selectUsers);
 8             session.setAttribute("pu", pu);
 9 
10         }