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davidmartinezbaruadavidmartinezbarua
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Merge pull request #18818 from martin-blazevic/article/BAEL-9099
[BAEL-9099] Different Ways to Get Servlet Context
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‎web-modules/jakarta-servlets-2/pom.xml‎

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</exclusion>
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</exclusions>
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</dependency>
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<dependency>
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<groupId>org.eclipse.jetty</groupId>
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<artifactId>jetty-server</artifactId>
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<version>${jetty.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.eclipse.jetty</groupId>
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<artifactId>jetty-servlet</artifactId>
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<version>${jetty.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.eclipse.jetty</groupId>
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<artifactId>jetty-client</artifactId>
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<version>${jetty.version}</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<jakarta.servlet-api.version>6.1.0</jakarta.servlet-api.version>
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<jakarta.servlet.jsp-api.version>4.0.0</jakarta.servlet.jsp-api.version>
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<jakarta.servlet.jsp.jstl-api.version>3.0.0</jakarta.servlet.jsp.jstl-api.version>
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<jetty.version>11.0.24</jetty.version>
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<gson.version>2.11.0</gson.version>
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<commons-fileupload2-jakarta-servlet6.version>2.0.0-M2</commons-fileupload2-jakarta-servlet6.version>
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</properties>

‎web-modules/jakarta-servlets-2/src/main/java/com/baeldung/context/ContextServlet.java‎

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package com.baeldung.context;
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import jakarta.servlet.ServletConfig;
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import jakarta.servlet.ServletContext;
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import jakarta.servlet.ServletException;
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import jakarta.servlet.annotation.WebServlet;
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import jakarta.servlet.http.HttpServlet;
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import jakarta.servlet.http.HttpServletRequest;
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import jakarta.servlet.http.HttpServletResponse;
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import java.io.IOException;
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@WebServlet(ContextServlet.PATH)
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public class ContextServlet extends HttpServlet {
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protected static final String PATH = "/context";
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protected static final String LABEL_FROM_HTTP_SERVLET = "1) From HttpServlet: ";
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protected static final String LABEL_FROM_SERVLET_CONFIG = "2) From ServletConfig: ";
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protected static final String LABEL_FROM_HTTP_SERVLET_REQUEST = "3) From HttpServletRequest: ";
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protected static final String LABEL_FROM_HTTP_SESSION = "4) From HttpSession: ";
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@Override
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protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
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resp.setContentType("text/plain");
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// 1. Direct Access From the Servlet
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ServletContext contextFromServlet = this.getServletContext();
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resp.getWriter()
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.println(LABEL_FROM_HTTP_SERVLET + contextFromServlet);
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resp.getWriter()
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.println();
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// 2. Accessing Through the ServletConfig
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ServletConfig config = this.getServletConfig();
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ServletContext contextFromConfig = config.getServletContext();
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resp.getWriter()
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.println(LABEL_FROM_SERVLET_CONFIG + contextFromConfig);
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resp.getWriter()
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.println();
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// 3. Getting the Context From the HttpServletRequest (Servlet 3.0+)
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ServletContext contextFromRequest = req.getServletContext();
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resp.getWriter()
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.println(LABEL_FROM_HTTP_SERVLET_REQUEST + contextFromRequest);
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resp.getWriter()
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.println();
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// 4. Retrieving Through the Session Object
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ServletContext contextFromSession = req.getSession()
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.getServletContext();
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resp.getWriter()
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.println(LABEL_FROM_HTTP_SESSION + contextFromSession);
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}
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}

‎web-modules/jakarta-servlets-2/src/test/java/com/baeldung/context/BaseServletTest.java‎

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package com.baeldung.context;
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import org.eclipse.jetty.client.HttpClient;
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import org.eclipse.jetty.server.Server;
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import org.eclipse.jetty.servlet.ServletContextHandler;
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import org.junit.jupiter.api.*;
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import java.net.InetSocketAddress;
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@TestInstance(TestInstance.Lifecycle.PER_CLASS)
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public abstract class BaseServletTest {
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protected HttpClient httpClient;
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protected Server server;
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protected int port() {
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return 0; // (random) available port
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}
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protected String host() {
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return "localhost";
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}
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protected String contextPath() {
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return "/";
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}
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@BeforeAll
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void startup() throws Exception {
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httpClient = new HttpClient();
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httpClient.start();
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ServletContextHandler context = prepareContextHandler();
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server = new Server(new InetSocketAddress(host(), port()));
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server.setHandler(context);
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server.start();
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}
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private ServletContextHandler prepareContextHandler() {
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ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
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context.setContextPath(contextPath());
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configure(context);
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return context;
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}
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protected abstract void configure(ServletContextHandler context);
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@AfterAll
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void shutdown() throws Exception {
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if (server != null) {
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server.stop();
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}
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if (httpClient != null) {
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httpClient.stop();
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}
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}
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protected String baseUri() {
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String uri = server.getURI()
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.toString();
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return uri.endsWith("/") ? uri.substring(0, uri.length() - 1) : uri;
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}
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}

‎web-modules/jakarta-servlets-2/src/test/java/com/baeldung/context/ContextServletUnitTest.java‎

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package com.baeldung.context;
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import org.apache.http.HttpStatus;
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import org.eclipse.jetty.client.api.ContentResponse;
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import org.eclipse.jetty.servlet.ServletContextHandler;
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import org.junit.jupiter.api.Test;
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import java.net.URI;
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import java.util.List;
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import java.util.Set;
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import java.util.stream.Collectors;
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import static org.junit.jupiter.api.Assertions.*;
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class ContextServletUnitTest extends BaseServletTest {
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private static final List<String> CONTEXT_LABELS = List.of(ContextServlet.LABEL_FROM_HTTP_SERVLET, ContextServlet.LABEL_FROM_SERVLET_CONFIG,
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ContextServlet.LABEL_FROM_HTTP_SERVLET_REQUEST, ContextServlet.LABEL_FROM_HTTP_SESSION);
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@Override
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protected void configure(ServletContextHandler ctx) {
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ctx.addServlet(ContextServlet.class, ContextServlet.PATH);
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}
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@Test
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void givenContextServlet_whenGetRequest_thenResponseContainsSameContextInstance() throws Exception {
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ContentResponse response = httpClient.GET(URI.create(baseUri() + ContextServlet.PATH));
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assertEquals(HttpStatus.SC_OK, response.getStatus());
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String body = response.getContentAsString();
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assertContextLinesIn(body);
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List<String> tokens = parseServletContextTokens(body);
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assertAllEqual(tokens);
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}
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private static void assertContextLinesIn(String body) {
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for (String label : CONTEXT_LABELS) {
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assertTrue(body.contains(label));
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}
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}
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private static List<String> parseServletContextTokens(String body) {
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List<String> targetLines = body.lines()
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.filter(line -> CONTEXT_LABELS.stream()
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.anyMatch(line::startsWith))
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.collect(Collectors.toList());
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assertEquals(CONTEXT_LABELS.size(), targetLines.size());
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return targetLines.stream()
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.map(line -> {
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int indexOf = line.indexOf(':');
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assertTrue(indexOf >= 0);
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return line.substring(indexOf + 1)
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.trim();
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})
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.collect(Collectors.toList());
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}
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private static void assertAllEqual(List<String> tokens) {
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Set<String> distinct = Set.copyOf(tokens);
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assertEquals(1, distinct.size());
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}
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}

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