我有一个：java.lang.NoClassDefFoundError：javax / enterprise / context / spi / Contextual with netbeans 12.0 + jsf 2.3 + apache-tomcat 9.0.37

问题描述

我正在学习JSF，我用JSF做了一个CRUD的简单示例，我正在使用以下代码：

Apache Netbeans 12.0。
JDK 13.0.2。
JSF 2.3。
Apache-tomcat-9.0.37。

代码如下：

Bean.java

<DropDownMenu>
   <MenuItem>  // Suppose this is selected
   <MenuItem>
<DropDownMenu>
   <MenuItem>  // onClick --> Select this and deselect all other selected buttons

Item.java

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.annotation.postconstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ManagedBean
@ViewScoped
public class Bean implements Serializable {

    private List<Item> list;
    private Item item = new Item();
    private boolean edit;

    @postconstruct
    public void init() {
        // list = dao.list();
        // Actually,you should retrieve the list from DAO. This is just for demo.
        list = new ArrayList<Item>();
        list.add(new Item(1L,"item1"));
        list.add(new Item(2L,"item2"));
        list.add(new Item(3L,"item3"));
    }

    public void add() {
        // dao.create(item);
        // Actually,the DAO should already have set the ID from DB. This is just for demo.
        item.setId(list.isEmpty() ? 1 : list.get(list.size() - 1).getId() + 1);
        list.add(item);
        item = new Item(); // Reset placeholder.
    }

    public void edit(Item item) {
        this.item = item;
        edit = true;
    }

    public void save() {
        // dao.update(item);
        item = new Item(); // Reset placeholder.
        edit = false;
    }

    public void delete(Item item) {
        // dao.delete(item);
        list.remove(item);
    }

    public List<Item> getList() {
        return list;
    }

    public Item getItem() {
        return item;
    }

    public boolean isEdit() {
        return edit;
    }

    // Other getters/setters are actually unnecessary. Feel free to add them though.

}

index.xhtml

public class Item {

    private long id;
    private String value;
    
    public Item(long id,String value) {
        this.id = id;
        this.value = value;
    }

    public Item() {        
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
    
}

当我运行代码时，出现以下错误：

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:h="http://java.sun.com/jsf/html">
    <h:head>
        <title>Really simple CRUD</title>
    </h:head>
    <h:body>
        <h3>List items</h3>
        <h:form rendered="#{not empty bean.list}">
            <h:dataTable value="#{bean.list}" var="item">
                <h:column><f:facet name="header">ID</f:facet>#{item.id}</h:column>
                <h:column><f:facet name="header">Value</f:facet>#{item.value}</h:column>
                <h:column><h:commandButton value="edit" action="#{bean.edit(item)}" /></h:column>
                <h:column><h:commandButton value="delete" action="#{bean.delete(item)}" /></h:column>
            </h:dataTable>
        </h:form>
        <h:panelGroup rendered="#{empty bean.list}">
            <p>Table is empty! Please add new items.</p>
        </h:panelGroup>
        <h:panelGroup rendered="#{!bean.edit}">
            <h3>Add item</h3>
            <h:form>
                <p>Value: <h:inputText value="#{bean.item.value}" /></p>
                <p><h:commandButton value="add" action="#{bean.add}" /></p>
            </h:form>
        </h:panelGroup>
        <h:panelGroup rendered="#{bean.edit}">
            <h3>Edit item #{bean.item.id}</h3>
            <h:form>
                <p>Value: <h:inputText value="#{bean.item.value}" /></p>
                <p><h:commandButton value="save" action="#{bean.save}" /></p>
            </h:form>
        </h:panelGroup>
    </h:body>
</html>

在此示例之前，我创建了另一个注册表格示例，一切正常。

解决方法

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