質問編集履歴
3
解決方法を追記いたしました
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AjaxでServletと連携する場合setAttributeはしない方がよろしいのでしょうか?
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### 追記
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mts10806さんの指摘どうりJSONデータを使用することで解決できたため以下にコードを載せます
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```JavaScript
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$ .ajax({ type : "POST",
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url : "Test",
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dataType : "json",
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success : function(data) {
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$("#a")
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for (j = 0; j < data.emp_list.length; j++) {
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$("#abcd")
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.append(
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"<tr><td>"
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+ data.emp_list[j].emp_id
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+"</td><td>"
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+ data.emp_list[j].emp_name
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+ "</td></tr>")
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}
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},
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```
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```Java
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package todo.controller;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.sql.Connection;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.Map;
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import javax.servlet.RequestDispatcher;
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import javax.servlet.ServletException;
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import javax.servlet.annotation.WebServlet;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import org.apache.jasper.tagplugins.jstl.core.Out;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.fasterxml.jackson.core.JsonProcessingException;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import todo.controller.db;
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/**
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* Servlet implementation class HelloServlet
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*/
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@WebServlet("/Test")
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public class Test extends HttpServlet {
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static Connection connection = null;
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static PreparedStatement preparedStatement = null;
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static ResultSet resultSet = null;
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ArrayList<Object> AllSearch_JSON = new ArrayList<Object>();
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private static final long serialVersionUID = 1L;
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String all_json = null;
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/**
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* @see HttpServlet#HttpServlet()
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*/
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public Test() {
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super();
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}
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/**
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* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
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*/
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public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
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doPost(request, response);
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}
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/**
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* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
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*/
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protected void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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try {
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ObjectMapper mapper = new ObjectMapper();
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String json = mapper.writeValueAsString(emp.EmployeeList());
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response.setContentType("application/json;charset=UTF-8");
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PrintWriter pw = response.getWriter();
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pw.print("{"+"\"emp_list\":"+json+"}");
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} catch (Exception e) {
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}
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}
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}
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```
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```json
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//作成したJSONデータ
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{
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"emp_list": [{
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"emp_id": 4,
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"emp_name": "田中太郎"
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}, {
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"emp_id": 5,
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"emp_name": "田中次郎"
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}, {
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"emp_id": 7,
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"emp_name": "田中三郎"
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}]
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}
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```
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2
classが同じだったため変更
test
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test
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@@ -158,7 +158,7 @@
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//Ajaxと連携するServlet
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public class HelloServlet extends HttpServlet {
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public class HelloServlet2 extends HttpServlet {
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1
加筆しました
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CHANGED
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test
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### 前提・実現したいこと
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-
AjaxでServletに通信を行いsetAttributeの内容を
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AjaxでServletに通信を行いsetAttributeの内容を描画したいのですがエラーが出て困っています。
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エラー理由は、最初に読み込むjspの中にクリック時に読み込むsetAttributeが入っているためだと推測されます。どのように改修すれば良いのか教えていただけませんか?
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```
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org.apache.jasper.JasperException: An exception occurred processing JSP page [/WEB-INF/view/index.jsp] at line [81]
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-
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Caused by: java.lang.NullPointerException
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```
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```java
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package todo.controller;
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/**
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* 最初に呼び出される
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*/
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@WebServlet("/HelloServlet")
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public class HelloServlet extends HttpServlet {
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```jsp
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//DBのAの値を描画
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<td id=abcd><%request.getAttribute("1")%><td>
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$(function() {
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$("#
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$("#Search").click(function() {
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// Ajax通信を開始する
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$.ajax({
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type : "POST",
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url : "Test",
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success : function() {
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console.log("成功");
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//DBのAの値を消してBの値に置き換える*NullPointerExceptionエラーが出る
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$("#abcd").empty().append(<%request.getAttribute("2")%>)
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},
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error : function() {
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console.log("失敗");}
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})
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});
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});
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```
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```Java
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//Ajaxと連携するServlet
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public class HelloServlet extends HttpServlet {
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private static final long serialVersionUID = 1L;
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/**
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* @see HttpServlet#HttpServlet()
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*/
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public HelloServlet() {
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176
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super();
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}
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/**
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* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
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186
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*/
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public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
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190
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doPost(request, response);
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}
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/**
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* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
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200
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*/
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protected void doPost(HttpServletRequest request, HttpServletResponse response)
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204
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throws ServletException, IOException {
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206
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try {
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//DBに接続する BはDBの値
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request.setAttribute("2","B")
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} catch (Exception e) {
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216
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e.printStackTrace();
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}
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}
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}
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197
227
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```
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198
228
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@@ -202,14 +232,8 @@
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202
232
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233
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### 試したこと
|
204
234
|
|
205
|
-
|
206
|
-
|
207
|
-
|
235
|
+
Ajaxと通信するServletのsetAttribute内変数を最初に読み込むServletと同じにしてエラーを表示しないようにしましたが結局nullが出ており読み込めませんでした。
|
208
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-
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209
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-
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-
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236
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+
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237
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+
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238
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+
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211
|
-
|
239
|
+
AjaxでServletと連携する場合setAttributeはしない方がよろしいのでしょうか?
|
212
|
-
|
213
|
-
|
214
|
-
|
215
|
-
ここにより詳細な情報を記載してください。
|