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Jsp+dao integration
2022-07-24 05:20:00 【x0757】
1 Accept data submitted by hyperlinks
<%-- Hyperlinks : How to transfer parameters of hyperlinks Use ?key=value&key=value--%>
<a href="indexDo02.jsp?name=ykq&age=18"> Connect </a>
2 How to solve the garbled code
<%
request.setCharacterEncoding("utf-8");
String name= request.getParameter("uname");
String pwd = request.getParameter("pwd");
UserDao userDao = new UserDao();
User user = userDao.findByNameAndPwd(name,pwd);
if(user!=null){
session.setAttribute("user",user);
response.sendRedirect("success.jsp");
}else{
response.sendRedirect("login.jsp?error=1");
}
%> Common coding :
ISO-8859-1: International Code But Chinese is not supported .
UTF-8: Universal code supports English, Chinese and traditional Chinese .---- Enterprise development uses UTF-8
GBK: Chinese code . Simplified Chinese and traditional Chinese .
GB2312: Chinese code But it supports simplified Chinese .
3 Page Jump
4 JSP+Dao Integrate
4.1 Sign in
<title>Title</title>
<script>
function reg(){
location.href='register.jsp';
}
</script>
</head>
<body>
<%
String error = request.getParameter("error");
if(error!=null&&"1".equals(error)){
out.print("<font color='red'> Wrong account or password </font>");
}
%>
<form action="loginDo.jsp" method="post">
account number ：<input type="text" name="uname"><br>
password ：<input type="password" name="pwd"><br>
<input type="submit" value=" Sign in ">
<input type="button" value=" register " onclick="reg()">
</form>
</body>
</html>
loginDo.jsp
<%
request.setCharacterEncoding("utf-8");
String name= request.getParameter("uname");
String pwd = request.getParameter("pwd");
UserDao userDao = new UserDao();
User user = userDao.findByNameAndPwd(name,pwd);
if(user!=null){
session.setAttribute("user",user);
response.sendRedirect("success.jsp");
}else{
response.sendRedirect("login.jsp?error=1");
}
%>4.2 register
<title> Registration page </title>
<script>
function checkUsername(){
var uname = document.getElementsByName("uname")[0].value;
if(uname==null || uname.trim()==""){
alert(" Please enter your account number ");
return false;
}
return true;
}
function checkPassword(){
var pwd=document.getElementsByName("pwd")[0].value;
if(pwd==null || pwd.trim()==""){
alert(" Please input a password ");
return false;
}
return true;
}
function checkRealname(){
var realname=document.getElementsByName("realname")[0].value;
if(realname==null || realname.trim()==""){
alert(" Please enter a name ");
return false;
}
return true;
}
function ck(){
if(checkUsername()&&checkPassword()&&checkRealname()){
return true;
}
return false;
}
</script>
</head>
<body>
<h1> Registration page </h1>
<form action ="registerDo.jsp" method="post" onsubmit="return ck()">
account number ：<input type="text" name="uname" onblur="checkUsername()"><br>
password ：<input type="password" name="pwd" onblur="checkPassword()"><br>
full name ：<input type="text" name="realname" onblur="checkRealname()"><br>
<input type="submit" value=" Submit ">
</form>reginsterDo.jsp
<%
request.setCharacterEncoding("utf-8");
String name =request.getParameter("uname");
String pwd = request.getParameter("pwd");
String realname = request.getParameter("realname");
UserDao userDao = new UserDao();
User user =new User(name,pwd,realname);
userDao.insert(user);
response.sendRedirect("login.jsp");
%>4.3 Delete
<%
String id = request.getParameter("id");
DepartmentDao departmentDao = new DepartmentDao();
departmentDao.delete(Integer.parseInt(id));
response.sendRedirect("success.jsp");
%>4.4 modify
<%
String id =request.getParameter("id");
DepartmentDao departmentDao = new DepartmentDao();
Department department = departmentDao.findById(Integer.parseInt(id));
%>
<form action="updateDo.jsp" method="post">
id Number :<input type="text" value="<%=department.getId()%>" name="id" /><br>
department :<input type="text" value="<%=department.getName()%>" name="deptname"/><br>
<input type="submit" value=" Confirm the change "/>
</form>updateDo.jsp
<%
request.setCharacterEncoding("utf-8");
String id= request.getParameter("id");
String name = request.getParameter("deptname");
DepartmentDao departmentDao = new DepartmentDao();
Department d = new Department();
d.setId(Integer.parseInt(id));
d.setName(name);
departmentDao.update(d);
response.sendRedirect("success.jsp");
%>4.5 add to
<form action ="addDo.jsp" method="post">
id Number :<input type="text" name="id"><br>
department ：<input type="text" name="deptname">
<input type="submit" value=" add to ">
</form>addDo.jsp
<%
request.setCharacterEncoding("utf-8");
String name =request.getParameter("deptname");
DepartmentDao departmentDao = new DepartmentDao();
Department department = new Department();
department.setName(name);
departmentDao.add(department);
response.sendRedirect("success.jsp");
%>5 Nine built-in objects
1. out object --- effect : Used to output information to the browser . Common methods : print();
2. request object -- effect : Request object . Common methods :getParameter(); setCharacterEncoding("") , getSession(): obtain session object .
3. session object --> effect : A conversation The same user shares the storage in session Data in . Common methods :setAttribute(key,value) getAttribute(key); removeAttribute(key), invalidate(); Make current session Invalid
4. response The response object --> Common methods : sendRedirect(). getWriter(): obtain out object .
5.pageContext object : Represents the current page object . It can share the data of the current page . You can get other 8 Built in objects .
6.application object : All users share the data stored by this object .
7.page object : Represents the object of the current page this.
8.config object : Used to get servlet Configuration information .
9.exception object : Exception object . If the object wants to use, the web page must be an exception page
6 Four domain objects
Data stored in different objects , The scope of action is different .
1. pageContext: Can store data , The scope of action is that the current page is valid . 2. request: Can store data , The scope of action is that the same request is valid .--- Request forwarding jump 3. session: Can store data , The scope is that the same session is valid .--- User information 4. application: Can store data , The scope of action is the same application . Save the data to application in , Wrong number, especially wrong Because the longer the storage time is, the longer the resources are used .
Understand modifiers public protected Default private
7 The difference between redirection and request forwarding
7.1 Redirect
7.2 Request forwarding
7.3 difference
1. The redirection address bar will change , And a new request object will be generated . Can't get request Saved data .
2. The request forwarding address bar will not change , And it uses the same request object . Can get request Saved data .
The longer the storage period , The longer it takes up resources . Generally, when we develop, most of our data are used to saving to request In the object . As long as a small amount of data is saved to session In the session . For example, when logging in, the user's information is saved to session In the session .
8 jstl Tag library and EL expression
8.1 el expression
EL expression --> effect : Get the data in the four domain objects .
grammar : ${xxxScope.key}
We originally passed xxx.getAttribute(key) You can also get the data in the four domains , Why even use EL expression , because EL Expression syntax is more concise . And later can be with our jstl Tag library . If EL Expression not found for key, Returns an empty string "".
EL Expression belongs to jsp Or explain later thymeleaf The grammar of
<%
// Store data into four domains
pageContext.setAttribute("name","pageContesxt The content of ");
request.setAttribute("name","request The content of ");
session.setAttribute("name","session The content of ");
application.setAttribute("name","application The content of ");
response.sendRedirect("b.jsp");
//request.getRequestDispatcher("b.jsp").forward(request,response);
%>
<hr>
adopt getAttribute() Get the contents of the four domain objects <br>
<%=pageContext.getAttribute("name")%><br>
<%=request.getAttribute("name")%><br>
<%=session.getAttribute("name")%><br>
<%=application.getAttribute("name")%><br>
<hr>
adopt el Expression to get the contents of the four domain objects <br>
${pageScope.name}<br>
${requestScope.name}<br>
${sessionScope.name}<br>
${applicationScope.name}<br>
<hr>
${name}<br>el expression You can also omit scope ${key} Which object will it get data from . The default from the pageContext Is the scan right key, If so, don't continue scanning , If not, continue scanning request, And so on .
8.2 jstl Tag library
There are some commonly used labels --- such as : Circular label Judgment labels .
The purpose of using these labels is to reduce jsp in java Add script code . Enterprises do not recommend that you jsp Too many <%%> This will make the web page more messy . At this time, someone provided JSTL Tag library .
How to use jstl Tag library :
(1)web Introduce... Into the project jstl Tag library dependency
(2) In the use of jstl Labeled jsp Introduce the tag library on the web page
<%--jsp The header of the web page is introduced jstl Core tag library --%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
(3) Use
<%
List<Student> list = new ArrayList<>();
list.add(new Student(1," Zhang San ",24," Shanghai ",1));
list.add(new Student(2," Li Si ",21," Hangzhou ",0));
list.add(new Student(3," Wang Wu ",20," Beijing ",1));
request.setAttribute("Students",list);
%>
<table border="1" width="500">
<tr>
<td> Number </td>
<td> full name </td>
<td> Address </td>
<td> Age </td>
<td> Gender </td>
</tr>
<c:forEach items="${Students}" var="s">
<tr>
<td>${s.id}</td>
<td>${s.name}</td>
<td>${s.age}</td>
<td>${s.address}</td>
<c:if test="${s.sex==0}">
<td> Woman </td>
</c:if>
<c:if test="${s.sex==1}">
<td> male </td>
</c:if>
</c:forEach>
</tr>9 servlet Control layer
9.1 What is? servlet?
Namely java Class code . It can introduce the data transmitted by the front-end page , At the same time, you can also respond the results of the back-end query to the front-end , So that the front end can display the data to jsp Webpage .
9.2 Why use servlet
9.3 How to use servlet
(0) introduce servlet-api.jar package
(1) Create a class and inherit HttpServlet Parent class .
public class HelloServlet extends HttpServlet {
}
(2) rewrite HttpServlet in service Method .--- Business processing .
// Parameters passed by the front end can be accepted You can also save the data queried by the back end and let the front end obtain
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
(3) Put custom servlet Configuration to web.xml In file
<servlet>
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.xzj.servlet.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>9.4 One servlet Handle multiple requests
If there are many different requests , Do we have to create one for each different request servlet Do you , If so, there will be many servlet class .addUser deleteUser updateUser. We should only create one for the same category servlet.
such as : Operations on user classes ,UserServlet Operation of student class StudentServlet. If you use one servlet. So how to distinguish what operation . We can pass a parameter to indicate what operation it is when jumping .
One table corresponds to one servlet.
One table corresponds to one dao and entity
9.5 Use jsp+el+jstl+servlet complete crud
9.6 servlet Life cycle of
Namely servlet The process from creation to initialization, then to service and finally to destruction . Namely servlet Life cycle of .
servlet Different methods will be implemented at different stages .
(1) Construction method ---->servlet Execute when created
(2) Initialization method --->servlet This method will be executed when some parameters are initialized after creation .
(3) Execution method --->servlet When called .
(4) Destruction method --->servlet Shut down .
Find out : No matter how many requests are sent , Constructor and initialization methods are executed only once . and service Every request is executed .
prove servlet It's a singleton mode . Save memory space .
When the server tomcat Restart or rewrite the deployment project , that servlet Will be destroyed
Above when you first visit through a browser servlet Will be created and initialized . You can also configure when tomcat Create and initialize at startup servlet.
10 filter Filter
What is a filter ?
Filter out some unwanted information , Let some desired information pass . for example : The filter screen of the cup , Stuck on the highway . Purifier .
Filters in programs ?
Let some legitimate requests pass through the filter , And intercept some request paths that do not meet the requirements . When the request reaches the filter , You can set some parameters for the request .
The principle of the filter
How to create filters
（1） Create a class and implement Filter Interface and rewrite the corresponding method
@WebFilter(filterName = "EncodingFilter",urlPatterns = "/*")
public class EncodingFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException {
req.setCharacterEncoding("utf-8");// Set the encoding of the request The received request parameters will not be garbled .
resp.setCharacterEncoding("utf-8");// Set the encoding of the response , The response data will not be garbled .
// release
filterChain.doFilter(req,resp);
}
@Override
public void destroy() {
}
}
(2) Login filter
@WebFilter(filterName = "LoginFilter", urlPatterns = "/*")
public class LoginFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException {
// Move down Some methods exist in subclasses .
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
// Get the request path
String path = request.getRequestURI();
//1. Judge whether the current request path is the path to be released
if(path.contains("/login.jsp")||path.contains("/UserServlet")){
filterChain.doFilter(req,resp);
return; // Termination of the method
}
//2. You must log in before you can release . How to determine whether to log in .
HttpSession session = request.getSession();
Object user = session.getAttribute("user");
if(user!=null){ // Indicates that the user has logged in
filterChain.doFilter(req,resp);
return;
}
//3. Go to the login page
response.sendRedirect("/web07/login.jsp");
}
@Override
public void destroy() {
}
}
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