Java CastError

Question

前提・実現したいこと

JavaのオブジェクトクラスをListにキャストしたい

発生している問題・エラーメッセージ

Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:626)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:515)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	jp.topgate.gourmetshibuya.servlet.IndexServlet.doGet(IndexServlet.java:41)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
根本原因

java.lang.ClassCastException: class beanList.RestaurantList cannot be cast to class java.util.List (beanList.RestaurantList is in unnamed module of loader org.apache.catalina.loader.ParallelWebappClassLoader @7bc10d84; java.util.List is in module java.base of loader 'bootstrap')
	org.apache.jsp.index_jsp._jspService(index_jsp.java:272)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	jp.topgate.gourmetshibuya.servlet.IndexServlet.doGet(IndexServlet.java:41)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

該当のソースコード

<section id="portfolio">
		<div class="container-fluid p-0">
			<div class="row no-gutters">
		エラー箇所<%List<RestaurantBean> reList = (List<RestaurantBean>)request.getAttribute("RestaurantInfo");
			Iterator<RestaurantBean> iterator = reList.iterator();
			RestaurantBean rb = new RestaurantBean();
			while(iterator.hasNext()){
			rb = iterator.next();%>
			<div class="col-lg-4 col-sm-6">
					<a class="portfolio-box" href="assets/img/portfolio/fullsize/1.jpg"><img
						class="img-fluid" src="assets/img/portfolio/thumbnails/1.jpg" alt="" />
						<div class="portfolio-box-caption">
						<div class="project-name"><%=rb.getName() %></div>
						</div></a>
				</div>
			<%} %>

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		RestaurantDao rdao = new RestaurantDao();
		RestaurantList rl = new RestaurantList();
		rl = rdao.getResutaurantLimit６();
		request.setAttribute("RestaurantInfo", rl);
		RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
		rd.forward(request, response);
	}

package beanList;

import java.util.ArrayList;
import java.util.List;

import jp.topgate.gourmetshibuya.beans.RestaurantBean;

public class RestaurantList {
	private List<RestaurantBean> resutaurantList;

	public RestaurantList() {
		// TODO 自動生成されたコンストラクター・スタブ
		resutaurantList = new ArrayList<RestaurantBean>();
	}

	public List<RestaurantBean> getResutaurantList() {
		return resutaurantList;
	}

	public void addResutaurantList(RestaurantBean rb) {
		resutaurantList.add(rb);
	}
}

package jp.topgate.gourmetshibuya.beans;

public class RestaurantBean {
	private int restaurant_id;
	private String name;
	private String place;
	private String phonenum;
	private String genres;
	private String photo;
	private int evaluation;
	private String business_hours;
	private String url;
	private String regular_holiday;
	private String content;

	public int getRestaurant_id() {
		return restaurant_id;
	}
	public void setRestaurant_id(int restaurant_id) {
		this.restaurant_id = restaurant_id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getPlace() {
		return place;
	}
	public void setPlace(String place) {
		this.place = place;
	}
	public String getPhonenum() {
		return phonenum;
	}
	public void setPhonenum(String phonenum) {
		this.phonenum = phonenum;
	}
	public String getGenres() {
		return genres;
	}
	public void setGenres(String genres) {
		this.genres = genres;
	}
	public String getPhoto() {
		return photo;
	}
	public void setPhoto(String photo) {
		this.photo = photo;
	}
	public int getEvaluation() {
		return evaluation;
	}
	public void setEvaluation(int evaluation) {
		this.evaluation = evaluation;
	}
	public String getBusiness_hours() {
		return business_hours;
	}
	public void setBusiness_hours(String business_hours) {
		this.business_hours = business_hours;
	}
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public String getRegular_holiday() {
		return regular_holiday;
	}
	public void setRegular_holiday(String regular_holiday) {
		this.regular_holiday = regular_holiday;
	}
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
}

補足情報（FW/ツールのバージョンなど）

Java11 Eclipse MYSQL

Answer 1

リストの実装でないものはリストにはできません。

設定したクラスにキャスト後にリスト取得のメソッドを呼び出してください。

Comments

[zeb_libia]

キャスト後にsetterを呼び出せば良いのでしょうか？

[momon-ga]

zeb_libiaさんのいう”setter"とは、提示ソースでいうとなんていうメソッドですか？

[zeb_libia]

すみません。getterですね...
RestaurantListクラスのです