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JSP action -- usebean action

2022-07-26 08:00:00 【Super Qi】

jsp action

useBean action

a. effect

​ Instantiate or find within the specified domain JavaBean object ： If it exists, it will be returned directly JavaBean References to objects . If it does not exist, instantiate one JavaBean Object and store it in the specified domain scope with the specified name . Used to connect to servlet and html file

b. Grammar format 

<jsp:useBean
       id="beanName"
       class="package.class"
       scope="page|request|application|seesion"
       type="class_or_interface_name"
       beanName="ser_filename"
             ></jsp:useBean>

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​ example ：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>useBean label </title>
</head>
<body>
1.<jsp:useBean id="clock" type="java.io.Serializable" beanName="java.util.Date"></jsp:useBean>
2.<jsp:useBean id="clock" class="java.util.Date"></jsp:useBean>
 The current time is ：<%=clock %>
</body>
</html>

c. scop Range properties

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2、getProperty action

a. effect

​ call get Method , Read the attribute value and Convert to string Post output

b. Grammar format 

<jsp:getProperty name="bName" property="pName"></jsp:getProperty>

​ name Property specifies JavaBean Object name , That is to say JavaBean Of id value
​ property Attribute specifies JavaBean The property name of the object
​ If JavaBean The value of an attribute of the object is null, Then read the attribute value It's a “null” String

3、setProperty action

a. effect

​ adopt setProperty Action settings JavaBean Property value of object

b. Grammar format 

1. <jsp:setPropetty name="bName" property="pName" value="{String|<%= expression %>}"></jsp:setPropetty>
	// Use value Value represents a string or expression 
2. <jsp:setProperty name="bName" property="pName" param="paraName( Form element name )"></jsp:setProperty>
	// The value of the form element used is JavaBean Attribute assignment 
3. <jsp:setProperty name="bName" property="*"></jsp:setProperty>
	// wildcard （*）, Assign a value to an attribute using the value of a form element with the same name

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c. The application of three grammatical formats 

1. <jsp:setPropetty name="bName" property="pName" value="{String|<%= expression %>}"></jsp:setPropetty>
/**Book**/
package myClass;

public class Book {
    
    private String bn;
    public Book() {
    
        super();
    }
    public String getBn() {
    
        return bn;
    }
    public void setBn(String bn) {
    
        this.bn = bn;
    }
}

/**book.jsp**/
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
<%--    <jsp:useBean id="book" class="myClass.Book" scope="request"></jsp:useBean>--%>
</head>
<body>
<jsp:useBean id="BeanID" class="myClass.Book" scope="page"></jsp:useBean>
<jsp:setProperty name="BeanID" property="bn" value=" Programming "></jsp:setProperty>
<jsp:getProperty name="BeanID" property="bn"/>
</body>
</html>


2. <jsp:setProperty name="bName" property="pName" param="paraName( Form element name )"></jsp:setProperty>
/**book.html**/
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>setProperty</title>
</head>
<body>
<form action="dispBook.jsp">
    <ul>
        <li>ISBN&nbsp;：<input type="text" name="bn"></li>
        <li> book &nbsp;&nbsp; name ：<input type="text" name="book"></li>
        <li> do &nbsp;&nbsp; person ：<input type="text" name="auth"></li>
        <li> Sold or not ：<input type="radio" name="sta" value="true"> yes 
            <input type="radio" name="sta" value="false"> no 
        </li>
        <li>
            <input type="submit" value=" Submit ">
            <input type="reset" value=" Cancel ">
        </li>
    </ul>
</form>
</body>
</html>
            
            
/**dispBook.jsp**/
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>setProperty</title>
</head>
<body>
<%-- utilize useBean Action instantiation object book--%>
<jsp:useBean id="book" class="myClass.BooksOne" scope="application"></jsp:useBean>
<%-- Use setProperty Actions use form element parameters book Attribute assignment --%>
<jsp:setProperty name="book" property="isbn" param="bn"></jsp:setProperty>
<jsp:setProperty name="book" property="bookName" param="book"></jsp:setProperty>
<jsp:setProperty name="book" property="bookAuthor" param="auth"></jsp:setProperty>
<jsp:setProperty name="book" property="salaStatus" param="sta"></jsp:setProperty>

<%-- Use geyProperty Action get object book The attribute value --%>
 International Standard Book Number ：<jsp:getProperty name="book" property="isbn"/><br>
 Title ：<jsp:getProperty name="book" property="bookName"/><br>
 author ：<jsp:getProperty name="book" property="bookAuthor"/><br>
 Sales status ：<jsp:getProperty name="book" property="salaStatus"/>
</body>
</html>
    
    
/**BooksOne**/
package myClass;

public class BooksOne {
    
    private String isbn;
    private String bookName;
    private String bookAuthor;
    private String salaStatus;

    public BooksOne() {
    
        super();
    }

    public String getIsbn() {
    
        return isbn;
    }

    public void setIsbn(String isbn) {
    
        this.isbn = isbn;
    }

    public String getBookName() {
    
        return bookName;
    }

    public void setBookName(String bookName) {
    
        this.bookName = bookName;
    }

    public String getBookAuthor() {
    
        return bookAuthor;
    }

    public void setBookAuthor(String bookAuthor) {
    
        this.bookAuthor = bookAuthor;
    }

    public String getSalaStatus() {
    
        return salaStatus;
    }

    public void setSalaStatus(String salaStatus) {
    
        this.salaStatus = salaStatus;
    }
}

3. <jsp:setProperty name="bName" property="*"></jsp:setProperty> // I don't think it's useful 
/**book2.html**/
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="dispBook.jsp">
    <ul>
        <li>ISBN&nbsp;：<input type="text" name="bn"></li>
        <li> book &nbsp;&nbsp; name ：<input type="text" name="book"></li>
        <li> do &nbsp;&nbsp; person ：<input type="text" name="auth"></li>
        <li> Sold or not ：<input type="radio" name="sta" value="true"> yes 
            <input type="radio" name="sta" value="false"> no 
        </li>
        <li>
            <input type="submit" value=" Submit ">
            <input type="reset" value=" Cancel ">
        </li>
    </ul>
</form>
</body>
</html>
            
          
/**dispBook2.jsp**/
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%-- utilize useBean Action instantiation object book--%>
<jsp:useBean id="book" class="myClass.BooksOne" scope="application"></jsp:useBean>
<%-- The form element is automatically given the same name book Attribute assignment --%>
<jsp:setProperty name="book" property="*"></jsp:setProperty>
<%-- Use geyProperty Action get object book The attribute value --%>
 International Standard Book Number ：<jsp:getProperty name="book" property="isbn"/><br>
 Title ：<jsp:getProperty name="book" property="bookName"/><br>
 author ：<jsp:getProperty name="book" property="bookAuthor"/><br>
 Sales status ：<jsp:getProperty name="book" property="salaStatus"/>
</body>
</html>

d. Homework

​ Create a class , And encapsulate the title and number of the book . Create another jsp page , Instantiate this class , And assign values to the title and number of the book respectively , Then get the corresponding values of the book name and book number and display them .

/**mybook.java**/
package myClass;

public class myBook {
    
    private String bn; // Book number 
    private String bookName; // Title 

    public myBook() {
    
        super();
    }

    public String getBn() {
    
        return bn;
    }

    public void setBn(String bn) {
    
        this.bn = bn;
    }

    public String getBookName() {
    
        return bookName;
    }

    public void setBookName(String bookName) {
    
        this.bookName = bookName;
    }
}

/**mybook.jsp**/
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<jsp:useBean id="mybook" class="myClass.myBook" scope="application"></jsp:useBean>
<%--<jsp:setProperty name="mybook" property="bn" value="2243"></jsp:setProperty>--%>
<%--<jsp:setProperty name="mybook" property="bookName" value="C Language "></jsp:setProperty>--%>

<%-- Book number ：<jsp:getProperty name="mybook" property="bn"--%>
<%--<br>--%>
<%-- Title ：<jsp:getProperty name="mybook" property="bookName"/>--%>
<%
    mybook.setBn("2243");
    mybook.setBookName("C Language ");
%>
<%
    out.println(" Book number ："+mybook.getBn()+"<br>"+" Title ："+mybook.getBookName());
%>
</body>
</html>
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https://yzsam.com/2022/201/202207181755114129.html

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