JSF数组nullPointerException
我是JSF新手,我正在尝试为培训中心编写一个简单的代码 在这个JSF代码中,当我加载页面时,subjects数组工作正常,但当我提交页面时,它会给我一个空指针异常,我不知道为什么会发生这种情况JSF数组nullPointerException,jsf,nullpointerexception,Jsf,Nullpointerexception,我是JSF新手,我正在尝试为培训中心编写一个简单的代码 在这个JSF代码中,当我加载页面时,subjects数组工作正常,但当我提交页面时,它会给我一个空指针异常,我不知道为什么会发生这种情况 **The Java Bean Code :** =============================================== College.java: =============================================== package Training_C
**The Java Bean Code :**
===============================================
College.java:
===============================================
package Training_Center;
import javax.faces.bean.ManagedBean;
@ManagedBean(name = "College")
public class College {
private int college; // College Number HardCoded from College.xhtml page(Drop Down List)
private String special[] = new String[4]; //specialization array (Radio Button)
private String specialTicked; //Variable to store the element value from special[] array
private String subjects[] = new String[4];//Subjects[] array ( Check Boxes )
public College() {
}
public int getCollege() {
return college;
}
public void setCollege(int college) {
this.college = college;
}
public String[] getSpecial() {
if (getCollege() == 0) { // AOU Unoversity
special[0] = "AAAA";
special[1] = "IT";
special[2] = "BBBB";
special[3] = "CCCC";
}
return special;
}
public String getSpecialTicked() {
return specialTicked;
}
public void setSpecialTicked(String specialTicked) {
this.specialTicked = specialTicked;
}
public String[] getSubjects() {
if ("IT".equals(specialTicked)) {
subjects[0] = "M105 Introduction To Java";
subjects[1] = "M257 Java OOP";
subjects[2] = "M275 PHP";
subjects[3] = "M180 Data Structure";
}
return subjects;
}
public void setSubjects(String[] subjects) {
this.subjects = subjects;
}
}
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College.xhtml page:
========================================================
<h:form >
<h:selectOneMenu value="#{College.college}" >
<f:selectItem itemValue="-1" itemLabel="...Select..." />
<f:selectItem itemValue="0" itemLabel="AOU University" />
</h:selectOneMenu>
<h:commandButton value="Show Subjects" action="ShowSubjects" />
</h:form>
=====================================================
ShowSubjects.xhtml page :
=====================================================
<h:form>
<h:selectOneRadio value="#{College.specialTicked}" layout="pageDirection" >
<f:selectItems value="#{College.special}" ></f:selectItems>
</h:selectOneRadio>
<h:commandButton value="Submit" action="subjects" />
</h:form>
========================================================
subjects..xhtml page : ( this page gives the exception when i click submit button)
======================================================
<h:form>
<h:selectManyCheckbox value="#{College.subjects}" layout="pageDirection" >
<f:selectItems value="#{College.subjects}" ></f:selectItems>
</h:selectManyCheckbox>
<h:commandButton value="Submit"/>
</h:form>
Thanks
**Java Bean代码:**
===============================================
College.java:
===============================================
成套培训中心;
导入javax.faces.bean.ManagedBean;
@ManagedBean(name=“College”)
公立学院{
private int college;//从college.xhtml页面硬编码的学院编号(下拉列表)
专用字符串专用[]=新字符串[4];//专用数组(单选按钮)
私有字符串specialTicked;//用于存储特殊[]数组中元素值的变量
私有字符串subjects[]=新字符串[4];//subjects[]数组(复选框)
公立学院(){
}
公共学院(){
返回学院;
}
公共学院(国际学院){
这个学院=学院;
}
公共字符串[]getSpecial(){
如果(getCollege()==0){//AOU大学
特别[0]=“AAAA”;
特殊[1]=“IT”;
特别[2]=“BBBB”;
特别[3]=“中交”;
}
退货特价;
}
公共字符串getSpecialTicked(){
返回特殊包装;
}
公共无效集合特殊勾选(字符串特殊勾选){
this.specialTicked=specialTicked;
}
公共字符串[]getSubjects(){
如果(“IT”.equals(specialTicked)){
主题[0]=“M105 Java简介”;
主题[1]=“M257 Java OOP”;
主题[2]=“M275 PHP”;
主题[3]=“M180数据结构”;
}
返回主题;
}
public void setSubjects(字符串[]主题){
这个。主题=主题;
}
}
=======================================================
College.xhtml页面:
========================================================
=====================================================
ShowSubjects.xhtml页面:
=====================================================
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主题..xhtml页面:(当我单击submit按钮时,该页面会出现异常)
======================================================
谢谢
托管bean作用域的可能重复项与您的使用方式不符。有关JSF作用域的信息,请参阅。另外,请仔细查看您的
及其相关的
。谢谢axemoi,我解决了它,而问题正是范围问题。再次感谢