The last one was rewritten IDEA 2021.2 new Java Web project and Tomcat deployment，

The next article is the core, the basic usage of JavaBean s and IDEA configuration

JavaBean overview

• JavaBean is a component that uses Java language mechanism to realize specific functions
• JavaBean is actually a Java class. Jsp can reduce the code redundancy in Jsp by accessing variables and calling methods in JavaBean
• The relationship between JSP, Serlet and JavaBean

• JavaBean is a special Java class. It follows the JavaBean API specification and implements the java.io.Serializable interface. It is a public class. The class must contain a parameterless constructor and provide set and get functions for attribute access

• JavaBean s need to be placed in the specified directory so that the server can find and execute them, generally Web Root/WEB-INF/classes

Reference JavaBean in JSP

jsp:useBean: load a javaBean that will be used in the JSP page

• use

<jsp:useBean id="name" class="package.class" scope="scope"/>

<jsp:useBean id="stu" class="YoungHD.StudentBean" scope="page">
...
</jsp:useBean>

• Where id is the reference name used to create javaBean; Class is used to specify the class of javaBean; scope is used to specify the range of JavaBeans. The default value is page.
• scope value range:
  1. Page, JavaBeans can only be used on the current page and will be destroyed when a new page is loaded.
  2. Request, which is used by javaBean when the user sends a request.
  3. Session, javaBean always exists in the session.
  4. Application, javaBean can be used in the whole application.

jsp:setProperty sets the javaBean property value specified in useBean

• Basic Usage

<jsp:setProperty property="PropertyName" name="BeanName" value="Value" param="Parameter"/>

• Where name specifies the id of the javaBean used in useBean; Property is used to specify the name of the property for which you want to set a value. Value specifies the value to set for the property. param specifies the value of the form element used to enter data.
• Note: the value attribute and param attribute cannot be used at the same time.
• give an example

<jsp:setProperty property="username" name="YoungHD" value="younghd"/>

<jsp:setProperty name="stu" property="username" param="username"></jsp:setProperty>

jsp:getProperty gets the property value specified in the javaBean

• Basic grammar

<jsp:getProperty name="BeanName" property="PropertyName" />

• Where name specifies the id of the javaBean used in useBean; Property specifies the property name of the javaBean to get
• Example: the two methods have the same effect

full name:<%=stu.getUsername()%><hr>
full name:<jsp:getProperty property="username" name="stu"/><hr>

Automatic generation and configuration of JavaBean s in IDEA

• Create JavaBean: create a package under the src directory in the project and create a Java class under the package (Note: you must create a package, you cannot create a Java class directly, otherwise you cannot import JavaBeans
• Configure the IDEA project, create the classes directory and set the export path. The export path is Web Root/WEB-INF/classes (press and hold F4 on the project)

• Automatically generate Getter and Setter methods: select variable: ALT+INSERT shortcut key or right-click variable

Actual combat: using JavaBean s to submit forms

• StudenBean.java section

package RioTian;

public class StudenBean implements java.io.Serializable {

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getSchool_id() {
        return school_id;
    }

    public void setSchool_id(String school_id) {
        this.school_id = school_id;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getCollege() {
        return college;
    }

    public void setCollege(String college) {
        this.college = college;
    }

    public String getMy_introduce() {
        return my_introduce;
    }

    public void setMy_introduce(String my_introduce) {
        this.my_introduce = my_introduce;
    }

    public String[] getLoves() {
        return loves;
    }

    public void setLoves(String[] loves) {
        this.loves = loves;
    }

    private String username,password,school_id,address,sex,college,my_introduce;
    private String []loves;
}

• index.HTML section

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Classmate information</title>
  <style>
    body{background-color: beige}
  </style>
  <link rel="stylesheet" type="text/css" href="../css/f5.css">
  <script src="../js/f5.js"></script>
</head>
<body>
<div align="center">
  <p id="t_head">Personal information form</p><br>
</div>
<div align="center">
  <form action="../index.jsp" method="post" name="form_1" onsubmit="return user_Check()" >
    full name:<input type="text" name="username"><hr>
    password:<input type="password" name="password" onchange="return pwd_check1()"><hr>
    Confirm:<input type="password" name="re_password" onchange="return pwd_check2()"><hr>
    Student No.:<input type="text" name="school_id"><hr>
    Dormitory:<input type="text" name="address"><hr>
    Gender:
    <input name="sex" type="radio" checked="checked" value="boy"/>male
    <input name="sex" type="radio" value="girl"/>female<hr>
    college:
    <select name="college" style="width: 15%">
      <option  value ="computer">Computer science and technology</option>
      <option  value ="math">Academy of Mathematics</option>
      <option  value="business">Business School</option>
      <option  value="art">College of Arts</option>
      <option  value="chemistry">Academy of Chemical Sciences</option>
    </select><hr>
    Hobbies:
    <input type="checkbox" name="loves" value="10">read
    <input type="checkbox" name="loves" value="20">Swimming
    <input type="checkbox" name="loves" value="30">music
    <input type="checkbox" name="loves" value="40">writing<hr>
    Personal profile:<textarea  name="my_introduce" rows="5"  style="width: 20%"></textarea><hr>
    <input type="submit" name="Submit1" value="register">
    <input type="reset" name="Submit2" value="Reset">
  </form>
</div>
</body>
</html>

• index.jsp section

<%--
  Created by IntelliJ IDEA.
  User: RioTian
  Date: 2021/11/4
  Time: 20:38
--%>
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="RioTian.StudenBean" %>
<!DOCTYPE html>
<html>
<head>
    <title>JavaBean Processing page</title>
    <style>
        body{
            background-color: beige;
        }
    </style>
</head>
<body>
<h1 style="align-content: center"> JavaBean Use of </h1>
<%request.setCharacterEncoding("UTF-8");//The client page is controlled as UTF-8% >
<jsp:useBean id="stu" class="RioTian.StudenBean">
    <jsp:setProperty name="stu" property="username" param="username"></jsp:setProperty>
    <jsp:setProperty name="stu" property="password" param="password"></jsp:setProperty>
    <jsp:setProperty name="stu" property="school_id" param="school_id"></jsp:setProperty>
    <jsp:setProperty name="stu" property="address" param="address"></jsp:setProperty>
    <jsp:setProperty name="stu" property="sex" param="sex"></jsp:setProperty>
    <jsp:setProperty name="stu" property="college" param="college"></jsp:setProperty>
    <jsp:setProperty name="stu" property="loves" param="loves"></jsp:setProperty>
    <jsp:setProperty name="stu" property="my_introduce" param="my_introduce"></jsp:setProperty>
</jsp:useBean>
Name: <%=stu.getUsername()%> <hr>
Name: <jsp:getProperty name="stu" property="username"/><hr>
Password: <jsp:getProperty name="stu" property="school_id"/><hr>
Stu_Id: <jsp:getProperty name="stu" property="school_id"/><hr>
Dormitory: <jsp:getProperty name="stu" property="address"/><hr>
Sex: <jsp:getProperty name="stu" property="sex"/><hr>
College: <jsp:getProperty name="stu" property="college"/><hr>
Loves: <%
     String []temp=stu.getLoves();
    for (int i = 0;i < stu.getLoves().length;i++){
        out.print(temp[i]+"--");
    }
%><hr>
Personal-Profile: <jsp:getProperty name="stu" property="my_introduce"/> <hr>
</body>
</html>