This article shares a message management system based on MVC+DAO, which includes addition, deletion, modification and query, and the query has all queries and fuzzy query by keywords. The specific content is as follows
package ;
import .* ;
import .* ;
public interface NoteDAO
{
// Add operations public void insert(Note note) throws Exception ;
// Modify the operation public void update(Note note) throws Exception ;
// Delete operation public void delete(int id) throws Exception ;
// Query by ID, mainly for update use public Note queryById(int id) throws Exception ;
// Query all public List queryAll() throws Exception ;
// Fuzzy query public List queryByLike(String cond) throws Exception ;
};
package ;
import .* ;
import .* ;
import .* ;
import .* ;
import .* ;
public class NoteDAOImpl implements NoteDAO
{
// Add operations public void insert(Note note) throws Exception
{
String sql = "INSERT INTO note(id,title,author,content) VALUES(note_sequ.nextVal,?,?,?)" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
(1,()) ;
(2,()) ;
(3,()) ;
() ;
() ;
}
catch (Exception e)
{
// (e) ;
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
}
// Modify the operation public void update(Note note) throws Exception
{
String sql = "UPDATE note SET title=?,author=?,content=? WHERE id=?" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
(1,()) ;
(2,()) ;
(3,()) ;
(4,()) ;
() ;
() ;
}
catch (Exception e)
{
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
}
// Delete operation public void delete(int id) throws Exception
{
String sql = "DELETE FROM note WHERE id=?" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
(1,id) ;
() ;
() ;
}
catch (Exception e)
{
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
}
// Query by ID, mainly for update use public Note queryById(int id) throws Exception
{
Note note = null ;
String sql = "SELECT id,title,author,content FROM note WHERE id=?" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
(1,id) ;
ResultSet rs = () ;
if(())
{
note = new Note() ;
((1)) ;
((2)) ;
((3)) ;
((4)) ;
}
() ;
() ;
}
catch (Exception e)
{
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
return note ;
}
// Query all public List queryAll() throws Exception
{
List all = new ArrayList() ;
String sql = "SELECT id,title,author,content FROM note" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
ResultSet rs = () ;
while(())
{
Note note = new Note() ;
((1)) ;
((2)) ;
((3)) ;
((4)) ;
(note) ;
}
() ;
() ;
}
catch (Exception e)
{
(e) ;
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
return all ;
}
// Fuzzy query public List queryByLike(String cond) throws Exception
{
List all = new ArrayList() ;
String sql = "SELECT id,title,author,content FROM note WHERE title LIKE ? or AUTHOR LIKE ? or CONTENT LIKE ?" ;
PreparedStatement pstmt = null ;
DataBaseConnection dbc = null ;
dbc = new DataBaseConnection() ;
try
{
pstmt = ().prepareStatement(sql) ;
(1,"%"+cond+"%") ;
(2,"%"+cond+"%") ;
(3,"%"+cond+"%") ;
ResultSet rs = () ;
while(())
{
Note note = new Note() ;
((1)) ;
((2)) ;
((3)) ;
((4)) ;
(note) ;
}
() ;
() ;
}
catch (Exception e)
{
(e) ;
throw new Exception("An error occurred during operation!!!") ;
}
finally
{
() ;
}
return all ;
}
};
package ;
import .* ;
import .* ;
import .* ;
import .* ;
import .* ;
public class NoteServlet extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException
{
(request,response) ;
}
public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException
{
("GB2312") ;
String path = "" ;
// Receive the parameter value to be operated String status = ("status") ;
if(status!=null)
{
// The parameters have content, then select the appropriate method // Query all operations if("selectall".equals(status))
{
try
{
("all",().queryAll()) ;
}
catch (Exception e)
{
}
path = "list_notes.jsp" ;
}
// Insert operation if("insert".equals(status))
{
// 1. Receive inserted information String title = ("title") ;
String author = ("author") ;
String content = ("content") ;
// 2. Instantiate VO objects Note note = new Note() ;
(title) ;
(author) ;
(content) ;
// 3. Call DAO to complete the database insertion operation boolean flag = false ;
try
{
().insert(note) ;
flag = true ;
}
catch (Exception e)
{}
("flag",new Boolean(flag)) ;
path = "insert_do.jsp" ;
}
// Query the operation by ID. Before modifying, you need to query the data first. if("selectid".equals(status))
{
// Receive parameters int id = 0 ;
try
{
id = (("id")) ;
}
catch(Exception e)
{}
try
{
("note",().queryById(id)) ;
}
catch (Exception e)
{
}
path = "" ;
}
// Update operation if("update".equals(status))
{
int id = 0 ;
try
{
id = (("id")) ;
}
catch(Exception e)
{}
String title = ("title") ;
String author = ("author") ;
String content = ("content") ;
Note note = new Note() ;
(id) ;
(title) ;
(author) ;
(content) ;
boolean flag = false ;
try
{
().update(note) ;
flag = true ;
}
catch (Exception e)
{}
("flag",new Boolean(flag)) ;
path = "update_do.jsp" ;
}
// Fuzzy query if("selectbylike".equals(status))
{
String keyword = ("keyword") ;
try
{
("all",().queryByLike(keyword)) ;
}
catch (Exception e)
{
}
path = "list_notes.jsp" ;
}
// Delete operation if("delete".equals(status))
{
// Receive parameters int id = 0 ;
try
{
id = (("id")) ;
}
catch(Exception e)
{}
boolean flag = false ;
try
{
().delete(id) ;
flag = true ;
}
catch (Exception e)
{}
("flag",new Boolean(flag)) ;
path = "delete_do.jsp" ;
}
}
else
{
// It means no parameters, illegal customer request }
(path).forward(request,response) ;
}
};
/*
<servlet>
<servlet-name>note</servlet-name>
<servlet-class></servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>note</servlet-name>
<url-pattern>/note/note_mvc/Note</url-pattern>
</servlet-mapping>
*/
list_notes.jsp
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import=".*"%>
<%@ page import=".*"%>
<html>
<head>
<title>MVC+DAO Message management program——Log in</title>
</head>
<body>
<center>
<h1>Message management example —— MVC + DAOaccomplish</h1>
<hr>
<br>
<%
// Encoding conversion ("GB2312") ;
if(("uname")!=null)
{
// The user is logged in %>
<%
// If there is content, modify the variable i. If there is no, no content prompt will be made according to the value of i. int i = 0 ;
String keyword = ("keyword") ;
List all = null ;
all = (List)("all") ;
%>
<form action="Note" method="POST">
Please enter the query content：<input type="text" name="keyword">
<input type="hidden" name="status" value="selectbylike">
<input type="submit" value="Query">
</form>
</h3><a href="">Add a new message</a></h3>
<table width="80%" border="1">
<tr>
<td>messageID</td>
<td>title</td>
<td>author</td>
<td>content</td>
<td>delete</td>
</tr>
<%
Iterator iter = () ;
while(())
{
Note note = (Note)() ;
i++ ;
// Perform a loop printing to print out all the contents in the form of a table // Get content from the database int id = () ;
String title = () ;
String author = () ;
String content = () ;
// Because the keywords need to be red, you need to receive query keywords here // String keyword = ("keyword") ;
if(keyword!=null)
{
// The data needs to be reddit title = (keyword,"<font color=\"red\">"+keyword+"</font>")
;
author = (keyword,"<font color=\"red\">"+keyword
+"</font>") ;
content = (keyword,"<font color=\"red\">"+keyword
+"</font>") ;
}
%>
<tr>
<td><%=id%></td>
<td><a href="Note?id=<%=id%>&status=selectid"><%=title%></a></td>
<td><%=author%></td>
<td><%=content%></td>
<td><a href="Note?id=<%=id%>&status=delete">delete</a></td>
</tr>
<%
}
// Determine whether the value of i changes. If it changes, it means there is content. Otherwise, there is no content. if(i==0)
{
// Make a prompt %>
<tr>
<td colspan="5">没有任何content！！！</td>
</tr>
<%
}
%>
</table>
<%
}
else
{
// The user is not logged in, prompt the user to log in and jump ("refresh","2;URL=") ;
%>
您还未Log in，请先Log in！！！<br>
两秒后自动跳转到Log in窗口！！！<br>
If there is no jump，Please press<a href="">here</a>！！！<br>
<%
}
%>
</center>
</body>
</html>
The above is all about this article, I hope it will be helpful to everyone's learning.