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java - servlet jsp 的警告 : StandardWrapperValve[jsp]: PWC1406: Servlet. service() 抛出异常 java.lang.NullPointerException

转载 作者:行者123 更新时间:2023-11-29 09:08:54 26 4
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我不断收到这个警告,在一个非常简单的 JSP/Bean 页面上,我正在为考试练习,我无法通过这个。

有人能指出我的愚蠢吗?

<html>
<head>

<title>JSP Page</title>
</head>
<h1>Enter Details!</h1>
<body>
<form action="Display.jsp" method="post">

<center>
Enter Name :<input type="text" name="Name"/><br/>
Etv :<input type="radio" name="Channel" value="Etv" /><br/>
Mnet :<input type="radio" name="Channel" value="Mnet" /><br/>
Mtv :<input type="radio" name="Channel" value="Mtv" /><br/>
FTV :<input type="radio" name="Channel" value="FTV" /><br/>
Blue :<input type="checkbox" name="Blue" value="1" /><br/>
Yellow :<input type="checkbox" name="Yellow" value="1" /><br/>
Green :<input type="checkbox" name="Green" value="1" /><br/>
Red :<input type="checkbox" name="Red" value="1" /><br/>
<br/>
<br/>

<input type="submit" value="Submit" />
</center>
</form>

</body>
</html>

我的Javabean:

package Beans;

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

import java.beans.*;
import java.io.Serializable;

/**
*
* @author Ross
*/
public class NewBean implements Serializable {

private String Name;
private String Channel;
private int Blue;
private int Yellow;
private int Green;
private int Red ;

public NewBean() {

}

public NewBean(String tName,String tChannel,int tBlue,int tYellow,int tGreen,int tRed) {

Name=tName;
Channel=tChannel;
Blue=tBlue;
Yellow=tYellow;
Green=tGreen;
Red=tRed;
}

public String getName(){
return this.Name;
}
public String getChannel(){
return this.Channel;
}
public int getBlue(){
return this.Blue;
}
public int getYellow(){
return this.Yellow;
}
public int getGreen(){
return this.Green;
}
public int getRed(){
return this.Red;
}
public void setName(String tName){
this.Name = tName;
}
public void setChannel(String tChannel){
this.Channel = tChannel;
}
public void setBlue(int tBlue){
this.Blue = tBlue;
}
public void setYellow(int tYellow){
this.Yellow = tYellow;
}
public void setGreen(int tGreen){
this.Green = tGreen;
}
public void setRed(int tRed){
this.Red = tRed;
}
}

我的 JSP 显示 javabean:

<html>
<head>

<title>Display</title>
</head>
<body>
<h1>Result</h1>
<center>
<jsp:useBean id="NewBean"class="Beans.NewBean">

<jsp:setProperty name="index" property="Name" param="Name"/>
<jsp:setProperty name="index" property="Channel" param="Channel"/>
<jsp:setProperty name="index" property="Blue" param="Blue"/>
<jsp:setProperty name="index" property="Yellow" param="Yellow"/>
<jsp:setProperty name="index" property="Green" param="Green"/>
<jsp:setProperty name="index" property="Red" param="Red"/>
</jsp:useBean>
<b>Displayed.</b>
<jsp:getProperty name="index" property="Name"/>
<jsp:getProperty name="index" property="Channel"/>
<jsp:getProperty name="index" property="Blue"/>
<jsp:getProperty name="index" property="Yellow"/>
<jsp:getProperty name="index" property="Green"/>
<jsp:getProperty name="index" property="Red"/>
</center>

</body>
</html>

最佳答案

您应该遵循变量的 java 命名约定(驼峰式大小写)。即

//private String Name;
private String name;

public void setName(String tName){
//this.Name = tName;
this.name = tName;
}

应该由小写的属性“name”引用:

<!-- jsp:setProperty name="index" property="Name" param="Name"/ -->
<jsp:setProperty name="index" property="name" param="Name"/>

关于java - servlet jsp 的警告 : StandardWrapperValve[jsp]: PWC1406: Servlet. service() 抛出异常 java.lang.NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13412888/

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