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プロジェクトのコネクタに問題があります。 TomcatのlibにMySQLコネクタを追加し、IntellijIDEAでプロジェクトのパスに追加しましたが、まだ問題があります。 stackoverlowの古いバージョンからの回答はここでは機能しませんでした。 ここにあるプロジェクトのクラス：JavaEE/Tomcat 9.0.0/IntellijIdea 2016.2：java.sql.SQLException：接続URL 'null'のクラス ''のJDBCドライバを作成できません
web.xmlのindex.jspを
<?xml version="1.0" encoding="UTF-8"?>
<web-app 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_3_1.xsd"
version="3.1">
<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/library</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
<context-param>
<param-name>javax.faces.CONFIG_FILES</param-name>
<param-value>/WEB-INF/context.xml</param-value>
</context-param>
<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>*.xhtml</url-pattern>
</servlet-mapping>
</web-app>
のcontext.xml
<?xml version="1.0" encoding="UTF-8"?>
<Context path="/myApp" docBase="myApp"
crossContext="true" reloadable="true" debug="1">
<Resource name="jdbc/library"
global="jbc/library"
auth="Container"
type="javax.sql.DataSource"
initialSize="10"
maxTotal="100"
maxIdle="30"
maxWaitMillis="10000"
username="root"
password="admin"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/library" />
</Context>
error.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Upss</title>
</head>
<body>
<h1>Something is wrong</h1>
<a href="index.jsp">Try again</a>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Library Viewer</title>
</head>
<body>
<h1>Biblioteka viewer</h1>
<form action="BookServlet" method="post">
<input placeHolder="ISBN" type="text" name="isbn">
<br>
<input placeHolder="Tytuł" type="text" name="title">
<br>
<input placeHolder="Opis" type="text" name="description">
<br>
Szukaj: <input type="radio" name="option" value="search"> Dodaj: <input type="radio" name="option" value="add">
Modyfikuj: <input type="radio" name="option" value="update"> Usuń: <input type="radio" name="option" value="delete">
<br>
<input type="submit" value="Wyślij">
</form>
</body>
</html>
はresult.jsp
<%@page import="pl.javastart.model.Book"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<% Book book = (Book)request.getAttribute("book"); %>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>Wynik zapytania <%= request.getAttribute("option") %></h1>
<p>W wyniku Twojego zapytania otrzymano następujacy wynik:</p>
<p>Title: <%= book.getTitle() %><br>
ISBN: <%= book.getIsbn() %><br>
Descrition: <%= book.getDescription() %></p>
</body>
</html>
Book.java
package pl.javastart.model;
public class Book {
private String isbn;
private String title;
private String description;
public String getIsbn() {
return isbn;
}
public void setIsbn(String isbn) {
this.isbn = isbn;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Book(){}
public Book(String isbn, String title, String desc){
this.isbn = isbn;
this.title = title;
description = desc;
}
}
BookServlet.java
package pl.javastart.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import pl.javastart.dao.BookDAO;
import pl.javastart.model.Book;
@WebServlet("/BookServlet")
public class BookServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
String isbn = request.getParameter("isbn");
String title = request.getParameter("title");
String description = request.getParameter("description");
String option = request.getParameter("option");
BookDAO dao = new BookDAO();
Book book = null;
String operation = null;
boolean result = false;
if("search".equals(option)) {
book = dao.read(isbn);
result = book!=null? true:false;
operation = "search";
} else if("add".equals(option)) {
book = new Book(isbn, title, description);
result = dao.create(book);
operation = "add";
} else if("update".equals(option)) {
book = new Book(isbn, title, description);
result = dao.update(book);
operation = "update";
} else if("delete".equals(option)) {
book = new Book(isbn, title, description);
result = dao.delete(book);
operation = "delete";
}
if(book != null && result) {
request.setAttribute("option", operation);
request.setAttribute("book", book);
request.getRequestDispatcher("result.jsp").forward(request, response);
} else {
request.getRequestDispatcher("error.jsp").forward(request, response);
}
}
}
BookDAO.java
package pl.javastart.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import pl.javastart.model.Book;
import pl.javastart.util.ConnectionProvider;
public class BookDAO {
private final static String CREATE = "INSERT INTO book(isbn, title, description) VALUES(?, ?, ?);";
private final static String READ = "SELECT isbn, title, description FROM book WHERE isbn = ?;";
private final static String UPDATE = "UPDATE book SET isbn=?, title=?, description=? WHERE isbn = ?;";
private final static String DELETE = "DELETE FROM book WHERE isbn=?;";
public boolean create(Book book) {
Connection conn = null;
PreparedStatement prepStmt = null;
boolean result = false;
try {
conn = ConnectionProvider.getConnection();
prepStmt = conn.prepareStatement(CREATE);
prepStmt.setString(1, book.getIsbn());
prepStmt.setString(2, book.getTitle());
prepStmt.setString(3, book.getDescription());
int rowsAffected = prepStmt.executeUpdate();
if (rowsAffected > 0) {
result = true;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
releaseResources(prepStmt, null, conn);
}
return result;
}
public Book read(String isbn) {
Connection conn = null;
PreparedStatement prepStmt = null;
ResultSet resultSet = null;
Book resultBook = null;
try {
conn = ConnectionProvider.getConnection();
prepStmt = conn.prepareStatement(READ);
prepStmt.setString(1, isbn);
resultSet = prepStmt.executeQuery();
if(resultSet.next()) {
resultBook = new Book();
resultBook.setIsbn(resultSet.getString("isbn"));
resultBook.setTitle(resultSet.getString("title"));
resultBook.setDescription(resultSet.getString("description"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
releaseResources(prepStmt, resultSet, conn);
}
return resultBook;
}
public boolean update(Book book) {
Connection conn = null;
PreparedStatement prepStmt = null;
boolean result = false;
try {
conn = ConnectionProvider.getConnection();
prepStmt = conn.prepareStatement(UPDATE);
prepStmt.setString(1, book.getIsbn());
prepStmt.setString(2, book.getTitle());
prepStmt.setString(3, book.getDescription());
prepStmt.setString(4, book.getIsbn());
int rowsAffected = prepStmt.executeUpdate();
if (rowsAffected > 0) {
result = true;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
releaseResources(prepStmt, null, conn);
}
return result;
}
public boolean delete(Book book) {
Connection conn = null;
PreparedStatement prepStmt = null;
boolean result = false;
try {
conn = ConnectionProvider.getConnection();
prepStmt = conn.prepareStatement(DELETE);
prepStmt.setString(1, book.getIsbn());
int rowsAffected = prepStmt.executeUpdate();
if (rowsAffected > 0) {
result = true;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
releaseResources(prepStmt, null, conn);
}
return result;
}
private void releaseResources(PreparedStatement prepStmt, ResultSet res,
Connection conn) {
try {
if (prepStmt != null && !prepStmt.isClosed()) {
prepStmt.close();
}
if (res != null && !res.isClosed()) {
res.close();
}
if (conn != null && !conn.isClosed()) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
接続Provider.java
package pl.javastart.util;
import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;
public class ConnectionProvider {
private static DataSource dataSource;
public static Connection getConnection() throws SQLException {
return getDSInstance().getConnection();
}
private static DataSource getDSInstance() {
if(dataSource == null) {
try {
Context initContext = new InitialContext();
Context envContext = (Context) initContext.lookup("java:comp/env");
dataSource = (DataSource) envContext.lookup("jdbc/library");
} catch (NamingException e) {
e.printStackTrace();
}
}
return dataSource;
}
}
Dao.iml
<?xml version="1.0" encoding="UTF-8"?>
<module type="JAVA_MODULE" version="4">
<component name="FacetManager">
<facet type="web" name="Web">
<configuration>
<descriptors>
<deploymentDescriptor name="web.xml" url="file://$MODULE_DIR$/web/WEB-INF/web.xml" />
</descriptors>
<webroots>
<root url="file://$MODULE_DIR$/web" relative="/" />
</webroots>
</configuration>
</facet>
</component>
<component name="NewModuleRootManager" inherit-compiler-output="true">
<exclude-output />
<content url="file://$MODULE_DIR$">
<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
</content>
<orderEntry type="inheritedJdk" />
<orderEntry type="sourceFolder" forTests="false" />
<orderEntry type="library" scope="PROVIDED" name="Tomcat 9.0.0.M9" level="application_server_libraries" />
<orderEntry type="library" name="mysql-connector-java-5.1.39-bin" level="project" />
</component>
</module>
ここでは、プロジェクト構造と画面です：
とコンソール：のcontext.xmlで
'DataSource'には、接続を取得するために必要なすべての情報が含まれています。 'String'パラメータは必要ありません。 –