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java - SelectOneMenu 没有任何可供选择的值

转载 作者：行者123 更新时间：2023-11-30 00:24:01 24 4
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当我尝试显示employee.jsp 页面时，我无法选择员工。看起来 SelectOneMenu 不起作用。我是否遗漏了该标签中的某些内容(第 20 行)？

我检查过，数据库中有员工表，其中包含一些员工数据。我已连接到数据库。我使用mysql数据库。您可以在 persistance.xml 文件中看到与此数据库的连接。


<%@ page language="java" contentType="text/html; 
charset=US-ASCII" pageEncoding="US-ASCII"%>
<%@ taglib prefix="f" uri="http://java.sun.com/jsf/core"%>
<%@ taglib prefix="h" uri="http://java.sun.com/jsf/html"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"    
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>Employee Details</title>
</head>
<body>
    <f:view>
    <h2><center>Welcome to Employee Home Page</center></h2>
    <br><br>
    <h:form>
    <h2>
        Select an Employee Number from the drop down:
    </h2>
    <br><br>
    <h:selectOneMenu id="selEmpNo"
        valueChangeListener="#{employee.employeeReport}"
        onchange="submit()">
        <f:selectItem itemLabel="select" />
    <f:selectItems value="#{employee.empNoList}" id="emp"/>
    </h:selectOneMenu>
    </h:form>
    <br><br>
    <h2>
    <h:outputText value="Employee Name: "></h:outputText>
    <h:outputText value="#{employee.empName}"/>
    <br><br>
    <h:outputText value="Employee Number: "/>
    <h:outputText value="#{employee.empNo}"/>
    <br><br>
    <h:outputText value="Name of the IBU: "/>
    <h:outputText value="#{employee.ibu}"/>
    <br><br>
    <h:outputText value="Designation: "/>
    <h:outputText value="#{employee.designation}"/> </h2>
</f:view>
</body>
</html>


<%@ page language="java" contentType="text/html;
charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>


<%@ taglib prefix="f" uri="http://java.sun.com/jsf/core"%>
<%@ taglib prefix="h" uri="http://java.sun.com/jsf/html"%>


<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
"http://www.w3.org/TR/html4/loose.dtd">

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
        <title>Home</title>
    </head>
    <body>
        <f:view>
            <h2>
                <center>
                <h:outputLabel> Welcome!!!</h:outputLabel>
                </center>
                <h:outputLink value="employee.jsp">Employee Details</h:outputLink>
            </h2>
        </f:view>
    </body>
</html>
</html>


package employee;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.faces.event.ValueChangeEvent;
import javax.faces.model.SelectItem;

public class EmployeeBean {

    private String empName;
    private String ibu;
    private String designation;
    private int empNo;
    //This is used to dynamically populate the drop down with employee numbers
    List<SelectItem> empNoList;
    List<EmployeeEntity>empList;

    public EmployeeBean(){
        this.empNoList = new ArrayList<SelectItem>();
        /*Populating Employee Number in the drop down - Dynamic */
        empList = new EmployeeService().getEmployeeList();
        Iterator<EmployeeEntity>iterator = empList.iterator();
        while(iterator.hasNext()){
            EmployeeEntity employee = iterator.next();
            SelectItem item = new SelectItem(employee.getEmpNo());
            empNoList.add(item);
        }
        System.out.println(empNoList);
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public String getIbu() {
        return ibu;
    }

    public void setIbu(String ibu) {
        this.ibu = ibu;
    }

    public String getDesignation() {
        return designation;
    }

    public void setDesignation(String designation) {
        this.designation = designation;
    }

    public int getEmpNo() {
        return empNo;
    }

    public void setEmpNo(int empNo) {
        this.empNo = empNo;
    }

    public List<SelectItem> getEmpNoList() {
        return empNoList;
    }

    public void setEmpNoList(List<SelectItem> empNoList) {
        this.empNoList = empNoList;
    }

    public List<EmployeeEntity> getEmpList() {
        return empList;
    }

    public void setEmpList(List<EmployeeEntity> empList) {
        this.empList = empList;

    }
    /*Eventlistener - for fetching an employee record based on the selection of employee
        number from the drop down*/
    public void employeeReport(ValueChangeEvent event){
        int empNo = Integer.parseInt((String)event.getNewValue());
        EmployeeEntity employee = new EmployeeService().getEmployee(empNo);
        this.empNo = employee.getEmpNo();
        this.empName = employee.getEmpName();
        this.ibu = employee.getIbu();
        this.designation = employee.getDesignation();
    }
}


  package employee;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="employee")
public class EmployeeEntity {

    @Id
    private int empNo;
    private String empName;
    private String ibu;
    private String designation;

    public int getEmpNo() {
        return empNo;
    }
    public void setEmpNo(int empNo) {
        this.empNo = empNo;
    }
    public String getEmpName() {
        return empName;
    }
    public void setEmpName(String empName) {
        this.empName = empName;
    }
    public String getIbu() {
        return ibu;
    }
    public void setIbu(String ibu) {
        this.ibu = ibu;
    }
    public String getDesignation() {
        return designation;
    }
    public void setDesignation(String designation) {
        this.designation = designation;
    }
}


package employee;

import java.util.ArrayList;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.persistence.Query;

public class EmployeeService {

    public List<EmployeeEntity> getEmployeeList(){
        List<EmployeeEntity> empList = new ArrayList<EmployeeEntity>();
        EntityManager em = null;
        try{
            EntityManagerFactory emf =
                    Persistence.createEntityManagerFactory("Employee-
                            Details");
            em = emf.createEntityManager();
            EntityTransaction et = em.getTransaction();
            et.begin();
            Query query = em.createQuery("select empNo from employee ");
            empList = query.getResultList();

        }
        catch(Exception e){
            //log the exception
        }
        return empList;
    }

    public EmployeeEntity getEmployee(int empNo){
        EmployeeEntity employee = new EmployeeEntity();
        EntityManager em = null;
        try{
            EntityManagerFactory emf =
                Persistence.createEntityManagerFactory("Employee-Details");
            em = emf.createEntityManager();
            EntityTransaction et = em.getTransaction();
            employee = em.find(EmployeeEntity.class, empNo);
        }
        catch(Exception e){
            //log the exception
        }
        finally{
            if( em != null){
                em.clear();
            }
        }
        return employee;
    }
}


<faces-config version="1.2"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-facesconfig_1_2.xsd">

    <navigation-rule>
       <display-name>Employee</display-name>
       <from-view-id>/index.jsp</from-view-id>
    </navigation-rule>
    <managed-bean>
            <managed-bean-name>employee</managed-bean-name>
            <managed-bean-class>employee.EmployeeBean
            </managed-bean-class>
            <managed-bean-scope>request</managed-bean-scope>
        </managed-bean>
</faces-config>


<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <display-name>Generating Employee Report</display-name>
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/faces/*</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>   
</web-app>


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最佳答案

您应该将 value 添加到 selectOneMenu，valueChangeListener 属性接受表示值更改监听器方法的方法绑定(bind)表达式当为此输入组件设置新值时收到通知。值更改监听器方法必须是采用 ValueChangeEvent 参数且返回类型为 void 的公共(public)方法。它与 value 属性不同。

您的页面。

<h:selectOneMenu id="selEmpNo"
    valueChangeListener="#{employee.employeeReport}"
    onchange="submit()" value="#{employee.myvalue}">
    <f:selectItem itemLabel="select" />
<f:selectItems value="#{employee.empNoList}" id="emp"/>
</h:selectOneMenu>

员工Bean

    package employee;

    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;
    import javax.faces.event.ValueChangeEvent;
    import javax.faces.model.SelectItem;

    public class EmployeeBean {

        private String myValue;
        private String empName;
        private String ibu;
        private String designation;

        public String getMyValue() {
            return myValue;
        }

        public void setMyValue(String myValue) {
            this.myValue = myValue;
        }

问候

来源here

关于java - SelectOneMenu 没有任何可供选择的值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23022912/

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