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Session Handling with Firestore tutorial. (#1746)
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‎session-handling/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Copyright 2019 Google LLC
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<project>
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<modelVersion>4.0.0</modelVersion>
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<packaging>war</packaging>
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<groupId>com.example.getstarted</groupId>
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<artifactId>session-handling</artifactId>
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<version>1.0-SNAPSHOT</version>
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<parent>
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<groupId>com.google.cloud.samples</groupId>
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<artifactId>shared-configuration</artifactId>
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<version>1.0.11</version>
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</parent>
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<properties>
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<gcloud.appId>MY_PROJECT</gcloud.appId>
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<failOnMissingWebXml>false</failOnMissingWebXml>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>11</maven.compiler.source>
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<maven.compiler.target>11</maven.compiler.target>
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<maven.compiler.showDeprecation>true</maven.compiler.showDeprecation>
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<maven.compiler.showWarnings>true</maven.compiler.showWarnings>
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<maven.compiler.failOnWarning>false</maven.compiler.failOnWarning>
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<maven.war.filteringDeploymentDescriptors>false</maven.war.filteringDeploymentDescriptors>
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<jetty.version>9.4.21.v20190926</jetty.version>
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</properties>
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<dependencies>
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<!-- https://mvnrepository.com/artifact/com.google.cloud/google-cloud-firestore -->
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<dependency>
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<groupId>com.google.cloud</groupId>
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<artifactId>google-cloud-firestore</artifactId>
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<version>0.52.0-beta</version>
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</dependency>
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<dependency>
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<groupId>javax.servlet</groupId>
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<artifactId>javax.servlet-api</artifactId>
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<version>4.0.0</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>23.0</version>
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<scope>compile</scope>
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</dependency>
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<dependency>
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<groupId>io.opencensus</groupId>
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<artifactId>opencensus-contrib-http-util</artifactId>
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<version>0.11.1</version>
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</dependency>
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<!-- Test dependencies -->
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.12</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.seleniumhq.selenium</groupId>
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<artifactId>selenium-server</artifactId>
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<version>3.3.1</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.seleniumhq.selenium</groupId>
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<artifactId>selenium-chrome-driver</artifactId>
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<version>3.3.1</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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<finalName>bookshelf-session-handling</finalName>
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<!-- Optional - for hot reload of the web application when using an IDE Eclipse / IDEA -->
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<outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes
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</outputDirectory>
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<plugins>
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<plugin>
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<groupId>org.eclipse.jetty</groupId>
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<artifactId>jetty-maven-plugin</artifactId>
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<version>${jetty.version}</version>
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</plugin>
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<plugin>
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<groupId>com.google.cloud.tools</groupId>
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<artifactId>jib-maven-plugin</artifactId>
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<version>1.7.0</version>
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<configuration>
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<to>
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<image>gcr.io/${gcloud.appId}/session-handling</image>
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</to>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

‎session-handling/src/main/java/com/example/gettingstarted/actions/HelloWorldServlet.java

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/* Copyright 2019 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.gettingstarted.actions;
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// [START session_handling_servlet]
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import java.io.IOException;
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import java.util.Random;
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import java.util.logging.Logger;
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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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@WebServlet(
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name = "helloworld",
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urlPatterns = {"/"})
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public class HelloWorldServlet extends HttpServlet {
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private static String[] greetings = {
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"Hello World", "Hallo Welt", "Ciao Mondo", "Salut le Monde", "Hola Mundo",
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};
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private static final Logger logger = Logger.getLogger(HelloWorldServlet.class.getName());
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@Override
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public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
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if (!req.getServletPath().equals("/")) {
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return;
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}
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// Get current values for the session.
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// If any attribute doesn't exist, add it to the session.
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Integer views = (Integer) req.getSession().getAttribute("views");
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if (views == null) {
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views = 0;
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}
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views++;
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req.getSession().setAttribute("views", views);
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String greeting = (String) req.getSession().getAttribute("greeting");
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if (greeting == null) {
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greeting = greetings[new Random().nextInt(greetings.length)];
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req.getSession().setAttribute("greeting", greeting);
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}
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logger.info("Writing response " + req.toString());
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resp.getWriter().write(String.format("%d views for %s", views, greeting));
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}
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}
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// [END session_handling_servlet]

‎session-handling/src/main/java/com/example/gettingstarted/util/FirestoreSessionFilter.java

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/* Copyright 2019 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.gettingstarted.util;
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import com.example.gettingstarted.actions.HelloWorldServlet;
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import com.google.cloud.firestore.CollectionReference;
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import com.google.cloud.firestore.DocumentSnapshot;
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import com.google.cloud.firestore.Firestore;
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import com.google.cloud.firestore.FirestoreOptions;
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import com.google.cloud.firestore.QueryDocumentSnapshot;
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import com.google.cloud.firestore.QuerySnapshot;
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import com.google.common.collect.Maps;
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import java.io.IOException;
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import java.math.BigInteger;
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import java.security.SecureRandom;
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import java.text.SimpleDateFormat;
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import java.util.Calendar;
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import java.util.Date;
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import java.util.Enumeration;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.concurrent.ExecutionException;
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import java.util.logging.Logger;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.annotation.WebFilter;
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import javax.servlet.http.Cookie;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import javax.servlet.http.HttpSession;
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@WebFilter(
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filterName = "FirestoreSessionFilter ",
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urlPatterns = {""})
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public class FirestoreSessionFilter implements Filter {
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private static final SimpleDateFormat dtf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
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private static final Logger logger = Logger.getLogger(HelloWorldServlet.class.getName());
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private static Firestore firestore;
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private static CollectionReference sessions;
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// [START sessions_handling_init]
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@Override
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public void init(FilterConfig config) throws ServletException {
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// Initialize local copy of datastore session variables.
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firestore = FirestoreOptions.getDefaultInstance().getService();
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sessions = firestore.collection("sessions");
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try {
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// Delete all sessions unmodified for over two days.
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Calendar cal = Calendar.getInstance();
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cal.setTime(new Date());
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cal.add(Calendar.HOUR, -48);
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Date twoDaysAgo = Calendar.getInstance().getTime();
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QuerySnapshot sessionDocs =
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sessions.whereLessThan("lastModified", dtf.format(twoDaysAgo)).get().get();
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for (QueryDocumentSnapshot snapshot : sessionDocs.getDocuments()) {
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snapshot.getReference().delete();
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}
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} catch (InterruptedException | ExecutionException e) {
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throw new ServletException("Exception initializing FirestoreSessionFilter.", e);
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}
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}
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// [END sessions_handling_init]
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// [START sessions_handling_filter]
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@Override
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public void doFilter(ServletRequest servletReq, ServletResponse servletResp, FilterChain chain)
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throws IOException, ServletException {
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HttpServletRequest req = (HttpServletRequest) servletReq;
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HttpServletResponse resp = (HttpServletResponse) servletResp;
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// For this app only call Firestore for requests to base path `/`.
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if (!req.getServletPath().equals("/")) {
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chain.doFilter(servletReq, servletResp);
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return;
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}
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// Check if the session cookie is there, if not there, make a session cookie using a unique
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// identifier.
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String sessionId = getCookieValue(req, "bookshelfSessionId");
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if (sessionId.equals("")) {
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String sessionNum = new BigInteger(130, new SecureRandom()).toString(32);
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Cookie session = new Cookie("bookshelfSessionId", sessionNum);
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session.setPath("/");
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resp.addCookie(session);
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}
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// session variables for request
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Map<String, Object> firestoreMap = null;
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try {
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firestoreMap = loadSessionVariables(req);
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} catch (ExecutionException | InterruptedException e) {
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throw new ServletException("Exception loading session variables.", e);
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}
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for (Map.Entry<String, Object> entry : firestoreMap.entrySet()) {
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servletReq.setAttribute(entry.getKey(), entry.getValue());
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}
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// Allow the servlet to process request and response
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chain.doFilter(servletReq, servletResp);
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// Create session map
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HttpSession session = req.getSession();
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Map<String, Object> sessionMap = new HashMap<>();
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Enumeration<String> attrNames = session.getAttributeNames();
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while (attrNames.hasMoreElements()) {
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String attrName = attrNames.nextElement();
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sessionMap.put(attrName, session.getAttribute(attrName));
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}
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logger.info(
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"Saving data to " + sessionId + " with views: " + session.getAttribute("views"));
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firestore.runTransaction((ob) -> sessions.document(sessionId).set(sessionMap));
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}
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// [END sessions_handling_filter]
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private String getCookieValue(HttpServletRequest req, String cookieName) {
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Cookie[] cookies = req.getCookies();
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if (cookies != null) {
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for (Cookie cookie : cookies) {
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if (cookie.getName().equals(cookieName)) {
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return cookie.getValue();
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}
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}
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}
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return "";
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}
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// [START sessions_load_session_variables]
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/**
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* Take an HttpServletRequest, and copy all of the current session variables over to it
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*
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* @param req Request from which to extract session.
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* @return a map of strings containing all the session variables loaded or an empty map.
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*/
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private Map<String, Object> loadSessionVariables(HttpServletRequest req)
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throws ExecutionException, InterruptedException {
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Map<String, Object> datastoreMap = new HashMap<>();
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String sessionId = getCookieValue(req, "bookshelfSessionId");
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if (sessionId.equals("")) {
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return datastoreMap;
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}
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return firestore
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.runTransaction(
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(ob) -> {
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DocumentSnapshot session = sessions.document(sessionId).get().get();
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Map<String, Object> data = session.getData();
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if (data == null) {
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data = Maps.newHashMap();
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}
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return data;
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})
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.get();
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}
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// [END sessions_load_session_variables]
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}

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