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泛型的使用

时间:2014-10-25 10:27:56      阅读:153      评论:0      收藏:0      [点我收藏+]

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目前这个项目使用的jsp+servlet+javabean,没有使用其它的框架。在处理数据库的时候,多张表就对应多个dao,而每个dao都有增删改查的方法,显得很冗余。于是写了一个CommonDao,其中包含了其他dao里面共有的一些方法。然后让其他的dao类继承CommonDao,servlet中直接使用CommonDao中的相应方法。那么这个时候遇到了一个问题,怎样判断需要对哪张表执行相应的操作。这时可以从servlet向dao类传入相应的sql,同时也需要判断传入的JavaBean对象,因为需要向sql中赋值。那么这个时候就需要使用泛型达到这一目的。

使用泛型时:

 1 public class CommonDao<T> {
 2     private ExecuteStatement executeStatement = new ExecuteStatement();
 3     private ReturnList returnList = new ReturnList();
 4     private T t;
 5     
 6     //添加数据到数据库
 7     public void add(T t, String sql) {
 8         Connection conn = null;
 9         PreparedStatement stmt = null;
10         try {
11             conn = DataBaseUtil.getConnection();
12             stmt = conn.prepareStatement(sql);
13             if(t instanceof Customer) {                            //判断泛型t的类型
14                 Customer customer = (Customer) t;
15                 stmt = executeStatement.setStatement(customer,stmt);
16             }
17             else if(t instanceof Person) {
18                 Person person = (Person) t;
19                 stmt = executeStatement.setStatement(person,stmt);
20             }
21             else if(t instanceof Department) {
22                 Department department = (Department) t;
23                 stmt = executeStatement.setStatement(department,stmt);
24             }
25             stmt.executeUpdate();
26         } catch (SQLException e) {
27             e.printStackTrace();
28         } finally {
29             DataBaseUtil.close(stmt, conn);
30         }
31     }

对应的其他dao:

 1 public class CustomerDao<T> extends CommonDao<T>{
 2     
 3     public CustomerDao() {
 4         
 5     }
 6     
 7     public void add(Customer customer) {
 8         Connection conn = null;
 9         PreparedStatement stmt = null;
10         String sql = "insert into SYSCUSTOMER(cuscode,cusname,cusdepcode,cuspercode,devdate,busdate,exitdate," +
11                 "cellphone,email,address,tenid,ufts) values(?,?,?,?,?,?,?,?,?,?,?,?)";
12         try {
13             conn = DataBaseUtil.getConnection();
14             stmt = conn.prepareStatement(sql);
15             stmt.setString(1, customer.getCusCode());
16             stmt.setString(2, customer.getCusName());
17             stmt.setString(3, customer.getCusDepCode());
18             stmt.setString(4, customer.getCusPerCode());
19             stmt.setString(5, customer.getDevDate());
20             stmt.setString(6, customer.getBusDate());
21             stmt.setString(7, customer.getExitDate());
22             stmt.setString(8, customer.getCellphone());
23             stmt.setString(9, customer.getEmail());
24             stmt.setString(10, customer.getAddress());
25             stmt.setString(11, customer.getTenId());
26             long currentTime = System.currentTimeMillis();            //获取当前时间,毫秒级别,距离1970年
27             Timestamp deptIsEnd = new Timestamp(currentTime);        //获取时间戳
28             stmt.setTimestamp(12, deptIsEnd);
29             stmt.executeUpdate();
30         } catch (SQLException e) {
31             e.printStackTrace();
32         } finally {
33             if(stmt != null) {
34                 DataBaseUtil.closeStatement(stmt);
35             }
36             if(conn != null) {
37                 DataBaseUtil.closeConnection(conn);
38             }
39         }
40     }
executeStatement.setStatement(customer,stmt)代码:
 1 //为customer表执行PreparedStatement方法
 2     public PreparedStatement setStatement(Customer customer, PreparedStatement stmt) {
 3         try {
 4             stmt.setString(1, customer.getCusCode());
 5             stmt.setString(2, customer.getCusName());
 6             stmt.setString(3, customer.getCusDepCode());
 7             stmt.setString(4, customer.getCusPerCode());
 8             stmt.setString(5, customer.getDevDate());
 9             stmt.setString(6, customer.getBusDate());
10             stmt.setString(7, customer.getExitDate());
11             stmt.setString(8, customer.getCellphone());
12             stmt.setString(9, customer.getEmail());
13             stmt.setString(10, customer.getAddress());
14             stmt.setString(11, customer.getTenId());
15             long currentTime = System.currentTimeMillis();            //获取当前时间,毫秒级别,距离1970年
16             Timestamp deptIsEnd = new Timestamp(currentTime);        //获取时间戳
17             stmt.setTimestamp(12, deptIsEnd);
18         } catch (SQLException e) {
19             e.printStackTrace();
20         }
21         return stmt;
22     }

CustomerServlet的add方法:

 1 /*
 2      * 功能:添加数据并返回到customer.jsp页面
 3      */
 4     @SuppressWarnings("unchecked")
 5     public void add(HttpServletRequest request, HttpServletResponse response) 
 6             throws ServletException, IOException {
 7         String cusCode = request.getParameter("cuscode");
 8         String cusName = null;
 9         try {
10             cusName = new String(request.getParameter("cusname").getBytes("ISO-8859-1"),"utf-8");
11         } catch (UnsupportedEncodingException e1) {
12             e1.printStackTrace();
13         }
14         String cusDepCode = request.getParameter("cusdepcode");
15         String cusPerCode = request.getParameter("cuspercode");
16         String devDate = request.getParameter("devdate");
17         String busDate = request.getParameter("busdate");
18         String exitDate = request.getParameter("exitdate");
19         Customer customer = new Customer();
20         customer.setCusCode(cusCode);
21         customer.setCusName(cusName);
22         customer.setCusDepCode(cusDepCode);
23         customer.setCusPerCode(cusPerCode);
24         customer.setDevDate(devDate);
25         customer.setBusDate(busDate);
26         customer.setExitDate(exitDate);
27         String sql = "insert into SYSCUSTOMER(cuscode,cusname,cusdepcode,cuspercode,devdate,busdate,exitdate," +
28                 "cellphone,email,address,tenid,ufts) values(?,?,?,?,?,?,?,?,?,?,?,?)";
29         //customerDao.add(customer);
30         customerDao.add(customer, sql);
31         select(request, response);
32         try {
33             response.sendRedirect("common/customer.jsp");
34         } catch (IOException e) {
35             e.printStackTrace();
36         }
37     }

这样就很好的解决了代码冗余的问题,当然后面还可以再优化。

 

泛型的使用

标签:style   blog   http   color   io   os   ar   使用   java   

原文地址:http://www.cnblogs.com/Aaronqcd/p/4049776.html

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