回忆简单的JSP用户管理

简单的jsp+servlet的web开发已经很少了~~但是开发流程对后来学框架还是挺有用的~~~

所以大概从简单的项目出发~~~简单的增删改查~~~~先好好理解好业务的流程~~~~
用的是简单的重复编程工作（重新封装->对象），所以大概就把源码跟步骤列一下好了~~~
连接类：JDBC_Connection.java

static{
try{
Class.forName(drivername);
System.out.println("创建驱动成功!");
}catch(ClassNotFoundException e){
System.out.println("创建驱动失败！请检查驱动!");
e.printStackTrace();
}
}
public static Connection getConnection(){}
public static void free(ResultSet rs,Connection conn,Statement stmt){}

在getConnection()方法中主要有这句（获得链接）：

conn = (Connection)DriverManager.getConnection(url, username, password);

用户操作：
（1）增加用户
addUser.jsp

主要有这句：

<form action="AddUserServlet" method="post" >

AddUser.java

public void add(UserVo userVo){
Connection conn = null;
PreparedStatement pstm = null;
ResultSet rs = null;
try{
conn = JDBC_Connection.getConnection();
String sql = "insert into user(id,name,age,tel,adress) value (?,?,?,?,?)";
pstm = conn.prepareStatement(sql);
pstm.setInt(1,userVo.getId());
pstm.setString(2, userVo.getName());
pstm.setInt(3, userVo.getAge());
pstm.setString(4, userVo.getTel());
pstm.setString(5, userVo.getAdress());

pstm.executeUpdate();
System.out.println("添加成功，添加的内容如下：");
System.out.println("id:"+userVo.getId()+"\t name:"+userVo.getName()+"\t age:"+userVo.getAge()+
"\t tel:"+userVo.getTel()+"\t adress:"+userVo.getAdress());
}catch(Exception e){
e.printStackTrace();
}finally{
JDBC_Connection.free(rs, conn, pstm);
}
}

AddUserServlet.java
注意：doPost(HttpServletRequest request, HttpServletResponse response)throws...{}

int id = Integer.parseInt(request.getParameter("id"));
String name = request.getParameter("name");
int age = Integer.parseInt(request.getParameter("age"));
String tel = request.getParameter("tel");
String adress = request.getParameter("adress");
UserVo userVo = new UserVo();
userVo.setId(id);
userVo.setName(name);
userVo.setAge(age);
userVo.setTel(tel);
userVo.setAdress(adress);
AddUser addUser = new AddUser();//声明一个AddUser对象
addUser.add(userVo);//调用AddUser对象的add()方法，
request.getRequestDispatcher("addUsers.jsp").forward(request, response);//转发到指定页面

在web.xml下的配置：

<servlet>
<servlet-name>AddUserServlet</servlet-name>
<servlet-class>com.cn.add.AddUserServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>AddUserServlet</servlet-name>
<url-pattern>/AddUserServlet</url-pattern>
</servlet-mapping>

（2）查询所有用户

Query.java

List<UserVo> list = new ArrayList<UserVo>();
try{
conn = JDBC_Connection.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from user");
while(rs.next()){
UserVo userVo = new UserVo();
userVo.setId(rs.getInt("id"));
userVo.setName(rs.getString("name"));
userVo.setAge(rs.getInt("age"));
userVo.setTel(rs.getString("tel"));
userVo.setAdress(rs.getString("adress"));

list.add(userVo);
}
}

ShowAllUserServlet.java

List<UserVo> list = new ArrayList<UserVo>();
Query query = new Query();
list = query.showUser();
request.setAttribute("list", list);     request.getRequestDispatcher("showAllUser.jsp").forward(request, response);

ShowAllUser.jsp

<c:forEach items = "${list }" var = "list">
<tr>
<td>${list.id }</td>
<td>${list.name }</td>
<td>${list.age }</td>
<td>${list.tel }</td>
<td>${list.adress }</td>
<td>
<a href="QueryUserByIdServlet?id=${list.id }">修改</a>
<a href="DeleteUserServlet?id=${list.id }">删除</a>
</td>
</tr>
</c:forEach>

(3)查询一个用户

QueryById.java

pstmt = conn.prepareStatement("select * from user where id = ?");
pstmt.setInt(1, id);
rs = pstmt.executeQuery();
return userVo;

QueryUserById.java

UserVo userVo = new UserVo();
QueryById queryById = new QueryById();
userVo = queryById.queryUserById(id);
request.setAttribute("userVo", userVo);     request.getRequestDispatcher("updateUser.jsp").forward(request, response);

UpdateUser.java

String sql = "update user set id = ?,name = ?,age = ?,tel = ?,address = ? where id = ?";

UpdateUserServlet.java

int id = Integer.parseInt(request.getParameter("id"));
String name = request.getParameter("name");
int age = Integer.parseInt(request.getParameter("age"));
String tel = request.getParameter("tel");
String adress =  request.getParameter("adress");
UserVo userVo =new UserVo();
userVo.setId(id);
userVo.setName(name);
userVo.setAge(age);
userVo.setTel(tel);
userVo.setAdress(adress);
UpdateUser updateUser = new UpdateUser();
updateUser.update(userVo);
response.sendRedirect("ShowAllUserServlet");

(4)删除用户
DeleteUser.java

String sql = "delete from user where id = ?";

DeleteUserServelt.java

int id = Integer.parseInt(request.getParameter("id"));
DeleteUser deleteUser = new DeleteUser();
deleteUser.deleteUser(id);
response.sendRedirect("ShowAllUserServlet");

关于中文的配置，还可以利用过滤器Filter
Zh_Filter.java

public class Zh_Filter implements Filter {
public void doFilter(ServletRequest request , ServletResponse response, FilterChain chain)
throws IOException, ServletException{
request.setCharacterEncoding("gb2312");
response.setCharacterEncoding("gb2312");
chain.doFilter(request, response);

}
}

在web.xml中配置

<filter>
<filter-name>filter</filter-name>
<filter-class>com.cn.filter.Zh_Filter</filter-class>
</filter>
<filter-mapping>
<filter-name>filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

另外，小知识点：

（1）网上提示关于servlet的forword和redirect的区别：
forward是服务器请求资源，服务器直接访问目标地址的URL，把那个URL的响应内容读取过来，然后把这些内容再发给浏览器，浏览器根本不知道服务器发送的内容是从哪儿来的，所以它的地址栏中还是原来的地址。

redirect就是服务端根据逻辑,发送一个状态码,告诉浏览器重新去请求那个地址，一般来说浏览器会用刚才请求的所有参数重新请求，所以session,request参数都可以获取。

Forward:request中的数据不会丢失，sendRedirect:request请求中的数据会丢失

前者仅是容器中控制权的转向，在客户端浏览器地址栏中不会显示出转向后的地址；后者则是完全的跳转，浏览器将会得到跳转的地址，并重新发送请求链接。这样，从浏览器的地址栏中可以看到跳转后的链接地址。所以，前者更加高效，在前者可以满足需要时，尽量使用forward()方法，并且，这样也有助于隐藏实际的链接。在有些情况下，比如，需要跳转到一个其它服务器上的资源，则必须使用sendRedirect()方法

（2）Request.getAttribute()是获取通过Request.setAttribute()中的数据

Request.getParameter()是获取表单请求过来的数据