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Retrieve data from database SQL (MariaDB) and insert that data in jsp file using Servlet Java [duplicate]

I'm implementing MVC using JSP and JDBC. I have imported a database class file to my JSP file and I would like to show the data of a DB table. I don't know how I should return the ResultSet from the Java class to the JSP page and embed it in HTML.
How can I achieve this?

In a well designed MVC approach, the JSP file should not contain any line of Java code and the servlet class should not contain any line of JDBC code.
Assuming that you want to show a list of products in a webshop, the following code needs to be created.
A Product class representing a real world entity of a product, it should be just a Javabean.
public class Product {
private Long id;
private String name;
private String description;
private BigDecimal price;
// Add/generate getters/setters/c'tors/equals/hashcode boilerplate.
}
A DAO class which does all the nasty JDBC work and returns a nice List<Product>.
public class ProductDAO {
private DataSource dataSource;
public ProductDAO(DataSource dataSource) {
this.dataSource = dataSource;
}
public List<Product> list() throws SQLException {
List<Product> products = new ArrayList<Product>();
try (
Connection connection = dataSource.getConnection();
PreparedStatement statement = connection.prepareStatement("SELECT id, name, description, price FROM product");
ResultSet resultSet = statement.executeQuery();
) {
while (resultSet.next()) {
Product product = new Product();
product.setId(resultSet.getLong("id"));
product.setName(resultSet.getString("name"));
product.setDescription(resultSet.getString("description"));
product.setPrice(resultSet.getBigDecimal("price"));
products.add(product);
}
}
return products;
}
}
A servlet class which obtains the list and puts it in the request scope.
#WebServlet("/products")
public class ProductsServlet extends HttpServlet {
#Resource(name="jdbc/YourDB") // For Tomcat, define as <Resource> in context.xml and declare as <resource-ref> in web.xml.
private DataSource dataSource;
private ProductDAO productDAO;
#Override
public void init() {
productDAO = new ProductDAO(dataSource);
}
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<Product> products = productDAO.list();
request.setAttribute("products", products); // Will be available as ${products} in JSP
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
} catch (SQLException e) {
throw new ServletException("Cannot obtain products from DB", e);
}
}
}
Finally a JSP file in /WEB-INF/products.jsp which uses JSTL <c:forEach> to iterate over List<Product> which is made available in EL by ${products}, and uses JSTL <c:out> to escape string properties in order to avoid XSS holes when it concerns user-controlled input.
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%# taglib uri="http://java.sun.com/jsp/jstl/format" prefix="fmt" %>
...
<table>
<c:forEach items="${products}" var="product">
<tr>
<td>${product.id}</td>
<td><c:out value="${product.name}" /></td>
<td><c:out value="${product.description}" /></td>
<td><fmt:formatNumber value="${product.price}" type="currency" currencyCode="USD" /></td>
</tr>
</c:forEach>
</table>
To get it to work, just call the servlet by its URL. Provided that the servlet is annotated #WebServlet("/products") or mapped in web.xml with <url-pattern>/products</url-pattern>, then you can call it by http://example.com/contextname/products
See also:
How to avoid Java code in JSP files?
doGet and doPost in Servlets
How should I connect to JDBC database / datasource in a servlet based application?
Design Patterns web based applications
RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()
How to map a ResultSet with unknown amount of columns to a List and display it in a HTML table?
How do I pass current item to Java method by clicking a hyperlink or button in JSP page?

MVC, in a web application context, doesn't consist in using a class from a JSP. It consists in using the following model :
browser sends a request to a web server
the web server is configured so that the request is handled by a servlet or a filter (the controller : Java code, not JSP code)
The servlet/filter usually dispatches the request to a specific class (called an Action, the specific part of the controller), based on configuration/annotations
The action executes the business logic (i.e. fetch the data from the database in your example : the model)
The action forwards the request to a JSP. The role of the JSP is only to generate HTML code (i.e. display your data : the view)
Since the JSP usually uses JSP tags (the JSTL, for example) and the JSP expression language, and since JSP tags and the EL are designed to get information from JavaBeans, you'd better have your data available in the form of JavaBeans or collections of JavaBeans.
The role of the controller (the action class) is thus to fetch the data, to create JavaBean instances containing the data, in a suitable format for the JSP, to put them in request attributes, and then to dispatch to the JSP. The JSP will then iterate through the JavaBean instances and display what they contain.
You should not implement the MVC framework yourself. Use existing ones (Stripes, Struts, etc.)

I don't know how should I return the ResultSet from the class file to the JSP page
Well, you don't.
The point of MVC is to separate your model ( the M DB info in this case ) from your view ( V a jsp, in this case ) in such a way you can change the view without braking to application.
To do this you might use an intermediate object to represent your data ( usually called DTO - after Data Transfer Object -, don't know how they call it these days ), and other object to fetch it ( usually a DAO ).
So basically you have your JSP file, get the request parameters, and then invoke a method from the DAO. The dao, internally has the means to connect to the db and fetch the data and builds a collections of DTO's which are returned to the JSP for rendering.
Something like this extremely simplified ( and insecure ) code:
Employee.java
class Employee {
String name;
int emplid;
}
EmployeeDAO.java
class EmployeeDAO {
... method to connect
etc.
List<Employee> getAllNamed( String name ) {
String query = "SELECT name, emplid FROM employee where name like ?";
ResultSet rs = preparedStatement.executeQuery etc etc.
List<Employee> results = ....
while( rs.hasNext() ) {
results.add( new Employee( rs.getString("name"), rs.getInt("emplid")));
}
// close resources etc
return results;
}
}
employee.jsp
<%
request.setAttribute("employees", dao.getAllNamed( request.getParameter("name") );
%>
<table>
<c:forEach items="${employees}" var="employee">
<tr><td>${employee.emplid}</td><td>${employee.name}</td></tr>
</c:forEach>
</table>
I hope this give you a better idea.

I have a problem. I don't understand clearly the code. I have a similar problem with my code.
I have created database SQL and filled up. Then I want to implement a MainServlet (code below) that richieve data from database and in a different jsp page, I want to insert that data in section like h1, h2 ecc... I must use the ${} sintax but I don't know how do that.
Briefly, In jsp file (code below, I MUST USE ${} SINTAX) I want to "call" MainServlet and there I want to richieve data from database and view in jsp file.
I hope I have explained correctly, thank you very much!
MainServlet.java
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MainServlet
*/
#WebServlet({ "/MainServlet" })
public class MainServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String PATH_JSP = "/WEB-INF/";
/**
* #see HttpServlet#HttpServlet()
*/
public MainServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
}
/**
* #see Servlet#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String doveAndare = request.getParameter("azione");
if(doveAndare==null)
doveAndare = "index";
try {
String driverString = "com.mysql.cj.jdbc.Driver";
Class.forName(driverString);
String connString = "jdbc:mysql://localhost:3306/ldd_jewels?user=root&password=";
Connection conn = DriverManager.getConnection(connString);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM JEWEL");
while (rs.next() == true) {
System.out.println(rs.getString("Category") + "\t" + rs.getString("Name"));
/* I try that but does not work
request.setAttribute("name", rs.getString("Name"));
javax.servlet.RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/widering_male.jsp");
dispatcher.forward(request, response); */
}
stmt.close();
conn.close();
} catch(Exception e) {
e.printStackTrace();
}
request.getRequestDispatcher(PATH_JSP+doveAndare+".jsp").forward(request, response);
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
doublerow.jsp
<section id="portfolio-details" class="portfolio-details">
<div class="container">
<div class="row gy-4">
<div class="col-lg-8">
<div class="portfolio-details-slider swiper">
<div class="swiper-wrapper align-items-center">
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_1.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_2.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_3.jpg" alt="" />
</div>
</div>
<div class="swiper-pagination"></div>
</div>
</div>
<div class="col-lg-4">
<div class="portfolio-info">
<h3>Product details</h3>
<ul>
<li><strong>Code</strong>: 1S3D5</li>
<li><strong>Category</strong>: Bracelets</li>
<li><strong>Name</strong>: Double Row Hinged Bangle</li>
<li><strong>Gender</strong>: Female</li>
<li><strong>Material</strong>: Yellow gold</li>
<li><strong>Size</strong>: 121mm</li>
<li><strong>Price</strong>: €5500</li>
</ul>
</div>
<div class="portfolio-description">
<h2>Description of product</h2>
<p>
The entwined ends of Tiffany Knot’s signature motif symbolize
the power of connections between people. Balancing strength
and elegance, each Tiffany Knot design is a complex feat of
craftsmanship. This bangle is crafted with yellow gold and
polished by hand for high shine. Wear on its own or partnered
with classic silhouettes for an unexpected pairing.
</p>
</div>
</div>
</div>
</div>
</section>
This is my database:
I want to insert each jewel in different pages (each jewel have a jsp file)

You can use the <c:forEach > tag
you can find a detailed example in the following link example use

I think it will be better for you to contain the data of the table into a collection such as list and return the list from the Java class and reuse this collection in the JSP.

Get user selected item from dynamic list in jsp page and pass to servlet [duplicate]

I have an HTML table with rows fetched from a database displayed in that table. I want the user to be able to delete a row by clicking on a delete hyperlink or button besides each row.
How do I invoke a JSP function on the page, when the user clicks on each of those delete hyperlinks or button, so that I can delete that row's entry from the database? What exactly should the <a> or <button> tag have to call the JSP function?
Note that I need to call a JSP function, not a JavaScript function.

Simplest way: just let the link point to a JSP page and pass row ID as parameter:
delete
And in delete.jsp (I'm leaving obvious request parameter checking/validating aside):
<% dao.delete(Long.valueOf(request.getParameter("id"))); %>
This is however a pretty poor practice (that was still an understatement) and due to two reasons:
HTTP requests which modifies the data on the server side should not be done by GET, but by POST. Links are implicit GET. Imagine what would happen when a web crawler like googlebot tries to follow all delete links. You should use a <form method="post"> and a <button type="submit"> for the delete action. You can however use CSS to style the button to look like a link. Edit links which just preload the item to prefill the edit form can safely be GET.
Putting business logic (functions as you call it) in a JSP using scriptlets (those <% %> things) is discouraged. You should use a Servlet to control, preprocess and postprocess HTTP requests.
Since you didn't tell any word about a servlet in your question, I suspect that you're already using scriptlets to load data from DB and display it in a table. That should also be done by a servlet.
Here's a basic kickoff example how to do it all. I have no idea what the table data represents, so let take Product as an example.
public class Product {
private Long id;
private String name;
private String description;
private BigDecimal price;
// Add/generate public getters and setters.
}
And then the JSP file which uses JSTL (just drop jstl-1.2.jar in /WEB-INF/lib to install it) to display the products in a table with an edit link and a delete button in each row:
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%# taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
...
<form action="products" method="post">
<table>
<c:forEach items="${products}" var="product">
<tr>
<td><c:out value="${fn:escapeXml(product.name)}" /></td>
<td><c:out value="${product.description}" /></td>
<td><fmt:formatNumber value="${product.price}" type="currency" currencyCode="USD" /></td>
<td>edit</td>
<td><button type="submit" name="delete" value="${product.id}">delete</button></td>
</tr>
</c:forEach>
</table>
add
</form>
Note the difference of approach: the edit link fires a GET request with an unique identifier of the item as request parameter. The delete button however fires a POST request instead whereby the unique identifier of the item is passed as value of the button itself.
Save it as products.jsp and put it in /WEB-INF folder so that it's not directly accessible by URL (so that the enduser is forced to call the servlet for that).
Here's how the servlet roughly look like (validation omitted for brevity):
#WebServlet("/products")
public class ProductsServlet extends HttpServlet {
private ProductDAO productDAO; // EJB, plain DAO, etc.
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
List<Product> products = productDAO.list();
request.setAttribute("products", products); // Will be available as ${products} in JSP.
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
}
#Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String delete = request.getParameter("delete");
if (delete != null) { // Is the delete button pressed?
productDAO.delete(Long.valueOf(delete));
}
response.sendRedirect(request.getContextPath() + "/products"); // Refresh page with table.
}
}
Here's how the add/edit form at /WEB-INF/product.jsp can look like:
<%# taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
...
<form action="product" method="post">
<label for="name">Name</label>
<input id="name" name="name" value="${fn:escapeXml(product.name)}" />
<br/>
<label for="description">Description</label>
<input id="description" name="description" value="${fn:escapeXml(product.description)}" />
<br/>
<label for="price">Price</label>
<input id="price" name="price" value="${fn:escapeXml(product.price)}" />
<br/>
<button type="submit" name="save" value="${product.id}">save</button>
</form>
The fn:escapeXml() is just there to prevent XSS attacks when edit data is redisplayed, it does exactly the same as <c:out>, only better suitable for usage in attribtues.
Here's how the product servlet can look like (again, conversion/validation omitted for brevity):
#WebServlet("/product")
public class ProductServlet extends HttpServlet {
private ProductDAO productDAO; // EJB, plain DAO, etc.
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String edit = request.getParameter("edit");
if (edit != null) { // Is the edit link clicked?
Product product = productDAO.find(Long.valueOf(delete));
request.setAttribute("product", product); // Will be available as ${product} in JSP.
}
request.getRequestDispatcher("/WEB-INF/product.jsp").forward(request, response);
}
#Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String save = request.getParameter("save");
if (save != null) { // Is the save button pressed? (note: if empty then no product ID was supplied, which means that it's "add product".
Product product = (save.isEmpty()) ? new Product() : productDAO.find(Long.valueOf(save));
product.setName(request.getParameter("name"));
product.setDescription(request.getParameter("description"));
product.setPrice(new BigDecimal(request.getParameter("price")));
productDAO.save(product);
}
response.sendRedirect(request.getContextPath() + "/products"); // Go to page with table.
}
}
Deploy and run it. You can open the table by http://example.com/contextname/products.
See also:
Our servlets wiki page (also contains an example with validation)
doGet and doPost in Servlets
Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern

How pass arrayList of Servlet to JSP? [duplicate]

I'm implementing MVC using JSP and JDBC. I have imported a database class file to my JSP file and I would like to show the data of a DB table. I don't know how I should return the ResultSet from the Java class to the JSP page and embed it in HTML.
How can I achieve this?

In a well designed MVC approach, the JSP file should not contain any line of Java code and the servlet class should not contain any line of JDBC code.
Assuming that you want to show a list of products in a webshop, the following code needs to be created.
A Product class representing a real world entity of a product, it should be just a Javabean.
public class Product {
private Long id;
private String name;
private String description;
private BigDecimal price;
// Add/generate getters/setters/c'tors/equals/hashcode boilerplate.
}
A DAO class which does all the nasty JDBC work and returns a nice List<Product>.
public class ProductDAO {
private DataSource dataSource;
public ProductDAO(DataSource dataSource) {
this.dataSource = dataSource;
}
public List<Product> list() throws SQLException {
List<Product> products = new ArrayList<Product>();
try (
Connection connection = dataSource.getConnection();
PreparedStatement statement = connection.prepareStatement("SELECT id, name, description, price FROM product");
ResultSet resultSet = statement.executeQuery();
) {
while (resultSet.next()) {
Product product = new Product();
product.setId(resultSet.getLong("id"));
product.setName(resultSet.getString("name"));
product.setDescription(resultSet.getString("description"));
product.setPrice(resultSet.getBigDecimal("price"));
products.add(product);
}
}
return products;
}
}
A servlet class which obtains the list and puts it in the request scope.
#WebServlet("/products")
public class ProductsServlet extends HttpServlet {
#Resource(name="jdbc/YourDB") // For Tomcat, define as <Resource> in context.xml and declare as <resource-ref> in web.xml.
private DataSource dataSource;
private ProductDAO productDAO;
#Override
public void init() {
productDAO = new ProductDAO(dataSource);
}
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<Product> products = productDAO.list();
request.setAttribute("products", products); // Will be available as ${products} in JSP
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
} catch (SQLException e) {
throw new ServletException("Cannot obtain products from DB", e);
}
}
}
Finally a JSP file in /WEB-INF/products.jsp which uses JSTL <c:forEach> to iterate over List<Product> which is made available in EL by ${products}, and uses JSTL <c:out> to escape string properties in order to avoid XSS holes when it concerns user-controlled input.
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%# taglib uri="http://java.sun.com/jsp/jstl/format" prefix="fmt" %>
...
<table>
<c:forEach items="${products}" var="product">
<tr>
<td>${product.id}</td>
<td><c:out value="${product.name}" /></td>
<td><c:out value="${product.description}" /></td>
<td><fmt:formatNumber value="${product.price}" type="currency" currencyCode="USD" /></td>
</tr>
</c:forEach>
</table>
To get it to work, just call the servlet by its URL. Provided that the servlet is annotated #WebServlet("/products") or mapped in web.xml with <url-pattern>/products</url-pattern>, then you can call it by http://example.com/contextname/products
See also:
How to avoid Java code in JSP files?
doGet and doPost in Servlets
How should I connect to JDBC database / datasource in a servlet based application?
Design Patterns web based applications
RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()
How to map a ResultSet with unknown amount of columns to a List and display it in a HTML table?
How do I pass current item to Java method by clicking a hyperlink or button in JSP page?

MVC, in a web application context, doesn't consist in using a class from a JSP. It consists in using the following model :
browser sends a request to a web server
the web server is configured so that the request is handled by a servlet or a filter (the controller : Java code, not JSP code)
The servlet/filter usually dispatches the request to a specific class (called an Action, the specific part of the controller), based on configuration/annotations
The action executes the business logic (i.e. fetch the data from the database in your example : the model)
The action forwards the request to a JSP. The role of the JSP is only to generate HTML code (i.e. display your data : the view)
Since the JSP usually uses JSP tags (the JSTL, for example) and the JSP expression language, and since JSP tags and the EL are designed to get information from JavaBeans, you'd better have your data available in the form of JavaBeans or collections of JavaBeans.
The role of the controller (the action class) is thus to fetch the data, to create JavaBean instances containing the data, in a suitable format for the JSP, to put them in request attributes, and then to dispatch to the JSP. The JSP will then iterate through the JavaBean instances and display what they contain.
You should not implement the MVC framework yourself. Use existing ones (Stripes, Struts, etc.)

I don't know how should I return the ResultSet from the class file to the JSP page
Well, you don't.
The point of MVC is to separate your model ( the M DB info in this case ) from your view ( V a jsp, in this case ) in such a way you can change the view without braking to application.
To do this you might use an intermediate object to represent your data ( usually called DTO - after Data Transfer Object -, don't know how they call it these days ), and other object to fetch it ( usually a DAO ).
So basically you have your JSP file, get the request parameters, and then invoke a method from the DAO. The dao, internally has the means to connect to the db and fetch the data and builds a collections of DTO's which are returned to the JSP for rendering.
Something like this extremely simplified ( and insecure ) code:
Employee.java
class Employee {
String name;
int emplid;
}
EmployeeDAO.java
class EmployeeDAO {
... method to connect
etc.
List<Employee> getAllNamed( String name ) {
String query = "SELECT name, emplid FROM employee where name like ?";
ResultSet rs = preparedStatement.executeQuery etc etc.
List<Employee> results = ....
while( rs.hasNext() ) {
results.add( new Employee( rs.getString("name"), rs.getInt("emplid")));
}
// close resources etc
return results;
}
}
employee.jsp
<%
request.setAttribute("employees", dao.getAllNamed( request.getParameter("name") );
%>
<table>
<c:forEach items="${employees}" var="employee">
<tr><td>${employee.emplid}</td><td>${employee.name}</td></tr>
</c:forEach>
</table>
I hope this give you a better idea.

I have a problem. I don't understand clearly the code. I have a similar problem with my code.
I have created database SQL and filled up. Then I want to implement a MainServlet (code below) that richieve data from database and in a different jsp page, I want to insert that data in section like h1, h2 ecc... I must use the ${} sintax but I don't know how do that.
Briefly, In jsp file (code below, I MUST USE ${} SINTAX) I want to "call" MainServlet and there I want to richieve data from database and view in jsp file.
I hope I have explained correctly, thank you very much!
MainServlet.java
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MainServlet
*/
#WebServlet({ "/MainServlet" })
public class MainServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String PATH_JSP = "/WEB-INF/";
/**
* #see HttpServlet#HttpServlet()
*/
public MainServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
}
/**
* #see Servlet#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String doveAndare = request.getParameter("azione");
if(doveAndare==null)
doveAndare = "index";
try {
String driverString = "com.mysql.cj.jdbc.Driver";
Class.forName(driverString);
String connString = "jdbc:mysql://localhost:3306/ldd_jewels?user=root&password=";
Connection conn = DriverManager.getConnection(connString);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM JEWEL");
while (rs.next() == true) {
System.out.println(rs.getString("Category") + "\t" + rs.getString("Name"));
/* I try that but does not work
request.setAttribute("name", rs.getString("Name"));
javax.servlet.RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/widering_male.jsp");
dispatcher.forward(request, response); */
}
stmt.close();
conn.close();
} catch(Exception e) {
e.printStackTrace();
}
request.getRequestDispatcher(PATH_JSP+doveAndare+".jsp").forward(request, response);
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
doublerow.jsp
<section id="portfolio-details" class="portfolio-details">
<div class="container">
<div class="row gy-4">
<div class="col-lg-8">
<div class="portfolio-details-slider swiper">
<div class="swiper-wrapper align-items-center">
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_1.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_2.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_3.jpg" alt="" />
</div>
</div>
<div class="swiper-pagination"></div>
</div>
</div>
<div class="col-lg-4">
<div class="portfolio-info">
<h3>Product details</h3>
<ul>
<li><strong>Code</strong>: 1S3D5</li>
<li><strong>Category</strong>: Bracelets</li>
<li><strong>Name</strong>: Double Row Hinged Bangle</li>
<li><strong>Gender</strong>: Female</li>
<li><strong>Material</strong>: Yellow gold</li>
<li><strong>Size</strong>: 121mm</li>
<li><strong>Price</strong>: €5500</li>
</ul>
</div>
<div class="portfolio-description">
<h2>Description of product</h2>
<p>
The entwined ends of Tiffany Knot’s signature motif symbolize
the power of connections between people. Balancing strength
and elegance, each Tiffany Knot design is a complex feat of
craftsmanship. This bangle is crafted with yellow gold and
polished by hand for high shine. Wear on its own or partnered
with classic silhouettes for an unexpected pairing.
</p>
</div>
</div>
</div>
</div>
</section>
This is my database:
I want to insert each jewel in different pages (each jewel have a jsp file)

You can use the <c:forEach > tag
you can find a detailed example in the following link example use

I think it will be better for you to contain the data of the table into a collection such as list and return the list from the Java class and reuse this collection in the JSP.

How do i implement a JSTL collection? [duplicate]

I'm implementing MVC using JSP and JDBC. I have imported a database class file to my JSP file and I would like to show the data of a DB table. I don't know how I should return the ResultSet from the Java class to the JSP page and embed it in HTML.
How can I achieve this?

In a well designed MVC approach, the JSP file should not contain any line of Java code and the servlet class should not contain any line of JDBC code.
Assuming that you want to show a list of products in a webshop, the following code needs to be created.
A Product class representing a real world entity of a product, it should be just a Javabean.
public class Product {
private Long id;
private String name;
private String description;
private BigDecimal price;
// Add/generate getters/setters/c'tors/equals/hashcode boilerplate.
}
A DAO class which does all the nasty JDBC work and returns a nice List<Product>.
public class ProductDAO {
private DataSource dataSource;
public ProductDAO(DataSource dataSource) {
this.dataSource = dataSource;
}
public List<Product> list() throws SQLException {
List<Product> products = new ArrayList<Product>();
try (
Connection connection = dataSource.getConnection();
PreparedStatement statement = connection.prepareStatement("SELECT id, name, description, price FROM product");
ResultSet resultSet = statement.executeQuery();
) {
while (resultSet.next()) {
Product product = new Product();
product.setId(resultSet.getLong("id"));
product.setName(resultSet.getString("name"));
product.setDescription(resultSet.getString("description"));
product.setPrice(resultSet.getBigDecimal("price"));
products.add(product);
}
}
return products;
}
}
A servlet class which obtains the list and puts it in the request scope.
#WebServlet("/products")
public class ProductsServlet extends HttpServlet {
#Resource(name="jdbc/YourDB") // For Tomcat, define as <Resource> in context.xml and declare as <resource-ref> in web.xml.
private DataSource dataSource;
private ProductDAO productDAO;
#Override
public void init() {
productDAO = new ProductDAO(dataSource);
}
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<Product> products = productDAO.list();
request.setAttribute("products", products); // Will be available as ${products} in JSP
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
} catch (SQLException e) {
throw new ServletException("Cannot obtain products from DB", e);
}
}
}
Finally a JSP file in /WEB-INF/products.jsp which uses JSTL <c:forEach> to iterate over List<Product> which is made available in EL by ${products}, and uses JSTL <c:out> to escape string properties in order to avoid XSS holes when it concerns user-controlled input.
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%# taglib uri="http://java.sun.com/jsp/jstl/format" prefix="fmt" %>
...
<table>
<c:forEach items="${products}" var="product">
<tr>
<td>${product.id}</td>
<td><c:out value="${product.name}" /></td>
<td><c:out value="${product.description}" /></td>
<td><fmt:formatNumber value="${product.price}" type="currency" currencyCode="USD" /></td>
</tr>
</c:forEach>
</table>
To get it to work, just call the servlet by its URL. Provided that the servlet is annotated #WebServlet("/products") or mapped in web.xml with <url-pattern>/products</url-pattern>, then you can call it by http://example.com/contextname/products
See also:
How to avoid Java code in JSP files?
doGet and doPost in Servlets
How should I connect to JDBC database / datasource in a servlet based application?
Design Patterns web based applications
RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()
How to map a ResultSet with unknown amount of columns to a List and display it in a HTML table?
How do I pass current item to Java method by clicking a hyperlink or button in JSP page?

MVC, in a web application context, doesn't consist in using a class from a JSP. It consists in using the following model :
browser sends a request to a web server
the web server is configured so that the request is handled by a servlet or a filter (the controller : Java code, not JSP code)
The servlet/filter usually dispatches the request to a specific class (called an Action, the specific part of the controller), based on configuration/annotations
The action executes the business logic (i.e. fetch the data from the database in your example : the model)
The action forwards the request to a JSP. The role of the JSP is only to generate HTML code (i.e. display your data : the view)
Since the JSP usually uses JSP tags (the JSTL, for example) and the JSP expression language, and since JSP tags and the EL are designed to get information from JavaBeans, you'd better have your data available in the form of JavaBeans or collections of JavaBeans.
The role of the controller (the action class) is thus to fetch the data, to create JavaBean instances containing the data, in a suitable format for the JSP, to put them in request attributes, and then to dispatch to the JSP. The JSP will then iterate through the JavaBean instances and display what they contain.
You should not implement the MVC framework yourself. Use existing ones (Stripes, Struts, etc.)

I don't know how should I return the ResultSet from the class file to the JSP page
Well, you don't.
The point of MVC is to separate your model ( the M DB info in this case ) from your view ( V a jsp, in this case ) in such a way you can change the view without braking to application.
To do this you might use an intermediate object to represent your data ( usually called DTO - after Data Transfer Object -, don't know how they call it these days ), and other object to fetch it ( usually a DAO ).
So basically you have your JSP file, get the request parameters, and then invoke a method from the DAO. The dao, internally has the means to connect to the db and fetch the data and builds a collections of DTO's which are returned to the JSP for rendering.
Something like this extremely simplified ( and insecure ) code:
Employee.java
class Employee {
String name;
int emplid;
}
EmployeeDAO.java
class EmployeeDAO {
... method to connect
etc.
List<Employee> getAllNamed( String name ) {
String query = "SELECT name, emplid FROM employee where name like ?";
ResultSet rs = preparedStatement.executeQuery etc etc.
List<Employee> results = ....
while( rs.hasNext() ) {
results.add( new Employee( rs.getString("name"), rs.getInt("emplid")));
}
// close resources etc
return results;
}
}
employee.jsp
<%
request.setAttribute("employees", dao.getAllNamed( request.getParameter("name") );
%>
<table>
<c:forEach items="${employees}" var="employee">
<tr><td>${employee.emplid}</td><td>${employee.name}</td></tr>
</c:forEach>
</table>
I hope this give you a better idea.

I have a problem. I don't understand clearly the code. I have a similar problem with my code.
I have created database SQL and filled up. Then I want to implement a MainServlet (code below) that richieve data from database and in a different jsp page, I want to insert that data in section like h1, h2 ecc... I must use the ${} sintax but I don't know how do that.
Briefly, In jsp file (code below, I MUST USE ${} SINTAX) I want to "call" MainServlet and there I want to richieve data from database and view in jsp file.
I hope I have explained correctly, thank you very much!
MainServlet.java
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MainServlet
*/
#WebServlet({ "/MainServlet" })
public class MainServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String PATH_JSP = "/WEB-INF/";
/**
* #see HttpServlet#HttpServlet()
*/
public MainServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
}
/**
* #see Servlet#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String doveAndare = request.getParameter("azione");
if(doveAndare==null)
doveAndare = "index";
try {
String driverString = "com.mysql.cj.jdbc.Driver";
Class.forName(driverString);
String connString = "jdbc:mysql://localhost:3306/ldd_jewels?user=root&password=";
Connection conn = DriverManager.getConnection(connString);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM JEWEL");
while (rs.next() == true) {
System.out.println(rs.getString("Category") + "\t" + rs.getString("Name"));
/* I try that but does not work
request.setAttribute("name", rs.getString("Name"));
javax.servlet.RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/widering_male.jsp");
dispatcher.forward(request, response); */
}
stmt.close();
conn.close();
} catch(Exception e) {
e.printStackTrace();
}
request.getRequestDispatcher(PATH_JSP+doveAndare+".jsp").forward(request, response);
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
doublerow.jsp
<section id="portfolio-details" class="portfolio-details">
<div class="container">
<div class="row gy-4">
<div class="col-lg-8">
<div class="portfolio-details-slider swiper">
<div class="swiper-wrapper align-items-center">
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_1.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_2.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_3.jpg" alt="" />
</div>
</div>
<div class="swiper-pagination"></div>
</div>
</div>
<div class="col-lg-4">
<div class="portfolio-info">
<h3>Product details</h3>
<ul>
<li><strong>Code</strong>: 1S3D5</li>
<li><strong>Category</strong>: Bracelets</li>
<li><strong>Name</strong>: Double Row Hinged Bangle</li>
<li><strong>Gender</strong>: Female</li>
<li><strong>Material</strong>: Yellow gold</li>
<li><strong>Size</strong>: 121mm</li>
<li><strong>Price</strong>: €5500</li>
</ul>
</div>
<div class="portfolio-description">
<h2>Description of product</h2>
<p>
The entwined ends of Tiffany Knot’s signature motif symbolize
the power of connections between people. Balancing strength
and elegance, each Tiffany Knot design is a complex feat of
craftsmanship. This bangle is crafted with yellow gold and
polished by hand for high shine. Wear on its own or partnered
with classic silhouettes for an unexpected pairing.
</p>
</div>
</div>
</div>
</div>
</section>
This is my database:
I want to insert each jewel in different pages (each jewel have a jsp file)

You can use the <c:forEach > tag
you can find a detailed example in the following link example use

I think it will be better for you to contain the data of the table into a collection such as list and return the list from the Java class and reuse this collection in the JSP.

Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern

I'm implementing MVC using JSP and JDBC. I have imported a database class file to my JSP file and I would like to show the data of a DB table. I don't know how I should return the ResultSet from the Java class to the JSP page and embed it in HTML.
How can I achieve this?

In a well designed MVC approach, the JSP file should not contain any line of Java code and the servlet class should not contain any line of JDBC code.
Assuming that you want to show a list of products in a webshop, the following code needs to be created.
A Product class representing a real world entity of a product, it should be just a Javabean.
public class Product {
private Long id;
private String name;
private String description;
private BigDecimal price;
// Add/generate getters/setters/c'tors/equals/hashcode boilerplate.
}
A DAO class which does all the nasty JDBC work and returns a nice List<Product>.
public class ProductDAO {
private DataSource dataSource;
public ProductDAO(DataSource dataSource) {
this.dataSource = dataSource;
}
public List<Product> list() throws SQLException {
List<Product> products = new ArrayList<Product>();
try (
Connection connection = dataSource.getConnection();
PreparedStatement statement = connection.prepareStatement("SELECT id, name, description, price FROM product");
ResultSet resultSet = statement.executeQuery();
) {
while (resultSet.next()) {
Product product = new Product();
product.setId(resultSet.getLong("id"));
product.setName(resultSet.getString("name"));
product.setDescription(resultSet.getString("description"));
product.setPrice(resultSet.getBigDecimal("price"));
products.add(product);
}
}
return products;
}
}
A servlet class which obtains the list and puts it in the request scope.
#WebServlet("/products")
public class ProductsServlet extends HttpServlet {
#Resource(name="jdbc/YourDB") // For Tomcat, define as <Resource> in context.xml and declare as <resource-ref> in web.xml.
private DataSource dataSource;
private ProductDAO productDAO;
#Override
public void init() {
productDAO = new ProductDAO(dataSource);
}
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<Product> products = productDAO.list();
request.setAttribute("products", products); // Will be available as ${products} in JSP
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
} catch (SQLException e) {
throw new ServletException("Cannot obtain products from DB", e);
}
}
}
Finally a JSP file in /WEB-INF/products.jsp which uses JSTL <c:forEach> to iterate over List<Product> which is made available in EL by ${products}, and uses JSTL <c:out> to escape string properties in order to avoid XSS holes when it concerns user-controlled input.
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%# taglib uri="http://java.sun.com/jsp/jstl/format" prefix="fmt" %>
...
<table>
<c:forEach items="${products}" var="product">
<tr>
<td>${product.id}</td>
<td><c:out value="${product.name}" /></td>
<td><c:out value="${product.description}" /></td>
<td><fmt:formatNumber value="${product.price}" type="currency" currencyCode="USD" /></td>
</tr>
</c:forEach>
</table>
To get it to work, just call the servlet by its URL. Provided that the servlet is annotated #WebServlet("/products") or mapped in web.xml with <url-pattern>/products</url-pattern>, then you can call it by http://example.com/contextname/products
See also:
How to avoid Java code in JSP files?
doGet and doPost in Servlets
How should I connect to JDBC database / datasource in a servlet based application?
Design Patterns web based applications
RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()
How to map a ResultSet with unknown amount of columns to a List and display it in a HTML table?
How do I pass current item to Java method by clicking a hyperlink or button in JSP page?

MVC, in a web application context, doesn't consist in using a class from a JSP. It consists in using the following model :
browser sends a request to a web server
the web server is configured so that the request is handled by a servlet or a filter (the controller : Java code, not JSP code)
The servlet/filter usually dispatches the request to a specific class (called an Action, the specific part of the controller), based on configuration/annotations
The action executes the business logic (i.e. fetch the data from the database in your example : the model)
The action forwards the request to a JSP. The role of the JSP is only to generate HTML code (i.e. display your data : the view)
Since the JSP usually uses JSP tags (the JSTL, for example) and the JSP expression language, and since JSP tags and the EL are designed to get information from JavaBeans, you'd better have your data available in the form of JavaBeans or collections of JavaBeans.
The role of the controller (the action class) is thus to fetch the data, to create JavaBean instances containing the data, in a suitable format for the JSP, to put them in request attributes, and then to dispatch to the JSP. The JSP will then iterate through the JavaBean instances and display what they contain.
You should not implement the MVC framework yourself. Use existing ones (Stripes, Struts, etc.)

I don't know how should I return the ResultSet from the class file to the JSP page
Well, you don't.
The point of MVC is to separate your model ( the M DB info in this case ) from your view ( V a jsp, in this case ) in such a way you can change the view without braking to application.
To do this you might use an intermediate object to represent your data ( usually called DTO - after Data Transfer Object -, don't know how they call it these days ), and other object to fetch it ( usually a DAO ).
So basically you have your JSP file, get the request parameters, and then invoke a method from the DAO. The dao, internally has the means to connect to the db and fetch the data and builds a collections of DTO's which are returned to the JSP for rendering.
Something like this extremely simplified ( and insecure ) code:
Employee.java
class Employee {
String name;
int emplid;
}
EmployeeDAO.java
class EmployeeDAO {
... method to connect
etc.
List<Employee> getAllNamed( String name ) {
String query = "SELECT name, emplid FROM employee where name like ?";
ResultSet rs = preparedStatement.executeQuery etc etc.
List<Employee> results = ....
while( rs.hasNext() ) {
results.add( new Employee( rs.getString("name"), rs.getInt("emplid")));
}
// close resources etc
return results;
}
}
employee.jsp
<%
request.setAttribute("employees", dao.getAllNamed( request.getParameter("name") );
%>
<table>
<c:forEach items="${employees}" var="employee">
<tr><td>${employee.emplid}</td><td>${employee.name}</td></tr>
</c:forEach>
</table>
I hope this give you a better idea.

I have a problem. I don't understand clearly the code. I have a similar problem with my code.
I have created database SQL and filled up. Then I want to implement a MainServlet (code below) that richieve data from database and in a different jsp page, I want to insert that data in section like h1, h2 ecc... I must use the ${} sintax but I don't know how do that.
Briefly, In jsp file (code below, I MUST USE ${} SINTAX) I want to "call" MainServlet and there I want to richieve data from database and view in jsp file.
I hope I have explained correctly, thank you very much!
MainServlet.java
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MainServlet
*/
#WebServlet({ "/MainServlet" })
public class MainServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String PATH_JSP = "/WEB-INF/";
/**
* #see HttpServlet#HttpServlet()
*/
public MainServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
}
/**
* #see Servlet#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String doveAndare = request.getParameter("azione");
if(doveAndare==null)
doveAndare = "index";
try {
String driverString = "com.mysql.cj.jdbc.Driver";
Class.forName(driverString);
String connString = "jdbc:mysql://localhost:3306/ldd_jewels?user=root&password=";
Connection conn = DriverManager.getConnection(connString);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM JEWEL");
while (rs.next() == true) {
System.out.println(rs.getString("Category") + "\t" + rs.getString("Name"));
/* I try that but does not work
request.setAttribute("name", rs.getString("Name"));
javax.servlet.RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/widering_male.jsp");
dispatcher.forward(request, response); */
}
stmt.close();
conn.close();
} catch(Exception e) {
e.printStackTrace();
}
request.getRequestDispatcher(PATH_JSP+doveAndare+".jsp").forward(request, response);
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
doublerow.jsp
<section id="portfolio-details" class="portfolio-details">
<div class="container">
<div class="row gy-4">
<div class="col-lg-8">
<div class="portfolio-details-slider swiper">
<div class="swiper-wrapper align-items-center">
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_1.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_2.jpg" alt="" />
</div>
<div class="swiper-slide">
<img src="assets/img/jewels/doublerow_3.jpg" alt="" />
</div>
</div>
<div class="swiper-pagination"></div>
</div>
</div>
<div class="col-lg-4">
<div class="portfolio-info">
<h3>Product details</h3>
<ul>
<li><strong>Code</strong>: 1S3D5</li>
<li><strong>Category</strong>: Bracelets</li>
<li><strong>Name</strong>: Double Row Hinged Bangle</li>
<li><strong>Gender</strong>: Female</li>
<li><strong>Material</strong>: Yellow gold</li>
<li><strong>Size</strong>: 121mm</li>
<li><strong>Price</strong>: €5500</li>
</ul>
</div>
<div class="portfolio-description">
<h2>Description of product</h2>
<p>
The entwined ends of Tiffany Knot’s signature motif symbolize
the power of connections between people. Balancing strength
and elegance, each Tiffany Knot design is a complex feat of
craftsmanship. This bangle is crafted with yellow gold and
polished by hand for high shine. Wear on its own or partnered
with classic silhouettes for an unexpected pairing.
</p>
</div>
</div>
</div>
</div>
</section>
This is my database:
I want to insert each jewel in different pages (each jewel have a jsp file)

You can use the <c:forEach > tag
you can find a detailed example in the following link example use

I think it will be better for you to contain the data of the table into a collection such as list and return the list from the Java class and reuse this collection in the JSP.