Spring 5.0 Cookbook: Recipes to build, test, and run Spring applications efficiently

All Java JDK installers are downloaded from Oracle's site at http://www.oracle.com/technetwork/java/javase/downloads/index.html.

To download JDK 1.8, perform the following steps:

The installed JDK will be the core language interpreter of Spring 5.0 projects, whether or not they are deployed to a Tomcat 9.x application server through Maven or Gradle. To read more about JDK 1.8, the reference http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html will provide you with some information about its highlights and will explain why it is popular nowadays in functional and reactive programming. More detailed concepts on functional programming will be discussed in Chapter 6, Functional Programming.

Visit the download page of Apache Tomcat application server https://tomcat.apache.org/download-native.cgi and click the Tomcat 9 link that will lead you to the download page.

The book will utilize Tomcat 9, which is the only Tomcat distribution that fully supports HTTP/2 without installing lots of third-party tools and modules. The following are the step-by-step details in setting up HTTP/2 in Tomcat 9:

Country name (two-letter code) [AU]:PH 
State or province name (full name) [Some-State]: Metro Manila 
Locality name (for example, city):Makati City 
Organization name (for example, company) [Internet Widgits  
Pty Ltd]:Packt Publishing 
Organizational unit name (for example, section): Spring 5.0 Cookbook 
Common name (for example, server FQDN or your name): 
Alibata Business Solutions and Training Services 
E-mail address: [email protected]

keytool -import -alias spring5server -file spring5packt.crt -keystore spring5server.keystore

keytool -import -alias spring5server -file spring5packt.crt -keystore "<Java1.8_folder>\Java1.8.112\jre\lib\security\cacerts" -storepass changeit

<Connector port="8443" 
protocol="org.apache.coyote.http11.Http11AprProtocol" 
maxThreads="150" SSLEnabled="true"> 
    <UpgradeProtocol 
    className="org.apache.coyote.http2.Http2Protocol"/> 
    <SSLHostConfig honorCipherOrder="false"> 
        <Certificate certificateKeyFile="conf/spring5packt.key" 
        certificateFile="conf/spring5packt.crt" 
        keyAlias="spring5server" type="RSA" /> 
    </SSLHostConfig> 
</Connector> 

 127.0.0.1 spring5server

Java 1.8 and Java 1.9 together with Spring 5.0 support HTTP/2 for the advancement of the JEE servlet container. This improvement is part of their JSR 369 specification which highlights the Servlet 4.0 specification. This Spring version is after Java 1.8's advance concurrency and stream support to run its functional and reactive modules. And since the core platform of Spring 5 is reactive, non-blocking and asynchronous, it needs NIO 2.0 threads of Tomcat 9.x's HTTP/2 for its project execution.

Since enabling HTTP/2 requires configuring TLS, browsers such as Firefox and Chrome will be restricted a bit by this TLS when it comes to running applications. These client browsers do not support clear text TCP; thus there is a need for secured HTTP (or HTTPS) which is the only way these browsers can utilize HTTP/2. And since TLS is enabled, there is a need for a keystore certificate that must be recognized by the application servers and accepted by the browsers in order to execute the request URLs.

OpenSSL for Windows is chosen as our certificate generator in creating TLS certificates. The book will use a self-signed certificate only, which is the easiest and most appropriate method so far in order to secure Apache Tomcat 9. This method no longer needs the certificate to be signed by a Certificate Authority (CA).

After generating the certificate, the certificate must be registered to both the keystore of the JRE and the custom keystore (for example, spring5keystore.keystore) of the application server. Keystores are used in the context of setting up the SSL connection in Java applications between client and server. They provide credentials, store private keys and certificates corresponding to the public keys of the applications and browsers. They are also required to access the secured server which usually triggers client authentication. The installed Java has its own keystore, which is <installation_folder>\Java1.8.112\jre\lib\security\cacerts. Always provide the official passwords in adding your certificates to these keystores. JRE has a default changeit password for its keystore.

The advantage of the TLS-enabled Tomcat 9 server is its support to JSR-369, which is the implementation of the Servlet 4.0 container. Moreover, the virtual hosting and multiple certificates are supported for a single connector, with each virtual host able to support multiple certificates. When the request-response transaction happens with HTTP/2, a session with multiple streams or threads of connections is created, as shown in the following code:

MetaData.Request metaData = new MetaData.Request("GET", HttpScheme.HTTP, new HostPortHttpField("spring5server: 8443" + server.getLocalport()), "/", HttpVersion.HTTP_2, new HttpFields()); 
HeadersFrame headersFrame = new HeadersFrame(1, metaData, null, 
true); 
session.newStream(headersFrame, new Promise.Adapter<Stream>(), new PrintingFramesHandler()); 
session.newStream(headersFrame, new Promise.Adapter<Stream>(), new PrintingFramesHandler()); 
session.newStream(headersFrame, new Promise.Adapter<Stream>(), new PrintingFramesHandler()); 

The whole concept of HTTP/2 transporting requests from client to server and responding back to its clients is depicted with the conceptual model as follows:

Visit the site https://spring.io/tools/sts/all and download the STS 3.8 release for Windows, Linux, or macOS. In our case, we will be opting for the Windows version. It is also available in 32-bit or 64-bit operating systems.

To get STS Eclipse 3.8, perform the following steps:

-Xms512m 
-Xmx1024m

STS Eclipse 3.8 is a customized all-in-one Eclipse-based distribution that provides support for Spring technologies such as Pivotal Cloud Foundry, Gradle, and Pivotal Server. Moreover, it is plugin-ready and contains language support, framework support, and runtime support for Java JDK 1.8 and Java EE 7.

The IDE has the following parts: views, perspectives, and the option menus. The view is the IDE's way of projecting its metadata or components graphically. Some views are console, debug, and task list, and data management views. The styling and the presence of the needed views depend on the type of perspective required for a particular project. A perspective is the logical arrangement of all these views. In our case, we have to choose a JEE perspective from the Window|Perspective | Open Perspective menu option to proceed with our programming.

But before we create our first project, always set the Java Runtime Environment to JDK's JRE. The JRE setting is located at Windows | Preferences and you need to Add... and choose the JDK's JRE as shown as follows:

You are now ready to create your Maven and Gradle project for our recipes in the next chapters.

Before creating the first Maven project, check first the JRE workspace configuration of your IDE. As noted in the previous recipe, the JRE of your Eclipse must be set to the JDK's JRE. Moreover, check the embedded version of Maven installed in STS Eclipse 3.8 through the Windows | Preferences panel. STS 3.8 will be using its embedded Maven 3.0 for the deployment operations. The list of Maven versions is available at https://maven.apache.org/.

Follow the steps to create Maven Projects for our succeeding code snippets as follows:

<build> 
  <finalName>ch01-spring5-cookbook</finalName> 
  <plugins> 
    <plugin> 
      <artifactId>maven-war-plugin</artifactId> 
      <version>2.3</version> 
      <configuration> 
        <failOnMissingWebXml>false</failOnMissingWebXml> 
      </configuration> 
    </plugin> 
  </plugins> 
</build> 

Apache Maven is already a built-in plugin in Eclipse and helps developers manage projects and use some build tools to clean, install, and deploy Eclipse projects. It has the main configuration file which is called the Project Object Model (POM) file.

POM is the fundamental unit of work in Maven that contains information and configuration details about the project. Some core information in POM is <modelVersion>, which currently must be set to 4.0.0, <groupId>, that identifies the project uniquely together with <projectId> and <versionId> across all projects in the Maven repository, <artifactId>, which is the name of the WAR file without the version, and <packaging>, which is WAR.

Later in this book, we will be adding <properties> and <dependencies> and <plugins> for our Spring 5.0 code recipes in our pom.xml file.

Install the Gradle module extension in our STS Eclipse 3.8 in order to clean, build, and deploy projects in Gradle. Perform the following steps:

After installing the Gradle STS extension, perform the following steps to install the Spring Gradle project:

apply plugin: 'eclipse'
apply plugin: "war"

sourceCompatibility = 1.8 
version = '1.0' 

war { 
    baseName = 'ch02-gradle' 
    version = '1.0' 
} 

sourceCompatibility = 1.8 

repositories { 
    mavenCentral() 
    jcenter() 
}

The most important configuration file in a Gradle project is the build.gradle. First, we have to add apply plugin: 'java' to tell Gradle that Java is the core language in building the scripts, testing the codes, executing compiled objects, creating Javadoc, and deploying JAR or WAR files. Since all project management and tooling depends on STS Eclipse, there is a need to add apply plugin: 'eclipse' in order to tell Gradle that all descriptors are Eclipse-specific and can be integrated and executed with Eclipse core and extension plugins. A by-product of its project installation and execution are the Eclipse folders such as .project, and .classpath. And since this is a web development project, we need to apply plugin: 'war' to indicate that the deployment is at WAR mode. Later on we will be adding some plugins needed in the development of our recipes.

In the properties section, the configuration must tell Gradle the version of the JDK through the sourceCompatibility property. Another property is the version of the WAR or project deployment, which is at first set to 1.0. Since the mode of deployment is the web, Java must know the name and the version of the WAR file to be generated.

On the repositories section, the configuration must define where to find the dependencies, which are at JCenter and MavenCentral.

At this point, the Tomcat 9 server must be running at https://localhost:8843/ in all browsers. Using OpenSSL, certificates are already installed in JRE's keystore and our server's keystore. Moreover, you have already successfully created your STS Maven project in order for us to configure your POM file.

Open the POM file of your Maven project and add the following details:

<plugin> 
  <groupId>org.apache.tomcat.maven</groupId> 
  <artifactId>tomcat7-maven-plugin</artifactId> 
  <version>2.2</version> 
  <configuration> 
    <url>https://spring5server:8443/manager/text</url> 
    <path>/ch01</path> 
    <keystoreFile>C:MyFilesDevelopmentServersTomcat9.0 
    confspring5server.keystore</keystoreFile> 
    <keystorePass>packt@@</keystorePass> 
    <update>true</update> 
    <username>packt</username> 
    <password>packt</password> 
  </configuration> 
</plugin>

The configuration detail starts with the <url> that sets Tomcat's plain-text-based administration interface used by Maven to invoke commands of the server. Maven needs to access the administration panel to allow the copy of the WAR file to the webapps. Since we will be using the TLS-enabled connector, we will be using the secured-HTTP together with the registered hostname in the keystore which is spring5server.

The tag <path> sets the context root of the project and must have a forward slash while the <username> and <password> refer to the credentials of the administrator having the roles manager-gui and manager-script.

The most important configuration details are <keystoreFile> and <keystorePass>. <keystoreFile> makes reference to the keystore of Tomcat that contains the TLS certificate. <keystorePass> provides the password used by <keystoreFile> in registering certificates. Together with these credentials, we have to be sure that the certificate has been added to the JRE's keystore which is <installation_folder>\Java1.8.112\jre\lib\security\cacerts.

<update> is required to undeploy all existing WAR files that already exist in the webapps. Sometimes the deployment does not work without this forced update.

Validate that your Tomcat with TLS-enabled connection is working by running https://localhost:8080/ on any browser. Also, check if your STS Gradle project is clean and updated.

buildscript { 
    repositories { 
        jcenter() 
    } 
    dependencies { 
        classpath 'com.bmuschko:gradle-tomcat-plugin:2.0' 
    } 
} 

apply plugin: 'com.bmuschko.tomcat' 
apply plugin: 'com.bmuschko.tomcat-base' 

dependencies { 
    def tomcatVersion = '9.0.0.M9' 
    tomcat "org.apache.tomcat.embed:tomcat-embed 
    core:${tomcatVersion}", 
    "org.apache.tomcat.embed:tomcat-embed-logging- 
    juli:${tomcatVersion}" 
    tomcat("org.apache.tomcat.embed:tomcat-embed- 
    jasper:${tomcatVersion}") { 
        exclude group: 'org.eclipse.jdt.core.compiler', 
             module: 'ecj' 
    } 
} 

tomcat { 
    httpsPort = 8443 
    enableSSL = true 
    users { 
        user { 
            username = 'packt' 
            password = 'packt' 
            roles = ['manager-gui', 'manager-script'] 
        } 
    } 
} 

task deploy (dependsOn: war){ 
    copy { 
        from "build/libs" 
        into 
        "C:\MyFiles\Development\Servers\Tomcat9.0\webapps" 
        include "*.war" 
    } 
} 

When it comes to building projects with conflicting versions of libraries, Gradle is one of those build tools that can satisfy any structure and state of project deployment and management. Since it is not written in XML, Gradle can provide logic in building classpath and project dependencies.

Gradle is efficient when it comes to incremental builds where the current and previous changes in deployment files are monitored. And when it comes to different repositories, Gradle can monitor changes of artifacts through effective repository-aware caches. In general, Gradle is advanced when it comes to repository management and project deployment than Maven.

Gradle is written in Groovy; thus, the build scripts are declarative, readable, and straightforward and can provide developers with easier conventions and philosophy of deployment.

First, Gradle must build the needed classpath libraries that are the main dependencies to the deployment, which happen to be com.bmuschko:gradle-tomcat-plugin:2.0. After building the external library, import the following plugins: com.bmuschko.tomcat and com.bmuschko.tomcat-base. Inject a closure to the tomcat() function that details all the needed configuration before the deployment. The custom Gradle task deploy takes all the configuration loaded by the tomcat() and war() functions. Running deploy in Gradle (STS) | Gradle Task Launcher will copy the WAR file found in build/libs to the Tomcat instance.

Visit the site http://dev.mysql.com/downloads/mysql/ to download the preferred community server for your projects. MySQL server is available in any operating system platform.

To deal with SQL transactions, we can us the CLI of MySQL or the given GUI-based MySQL Workbench:

Visit the site https://www.mongodb.com/download-center#community to download MongoDB under different operating system platforms. It also comes with SSL and no-SSL support.

The MongoDB server will be running with the default port 27017. In order to run the server, we type the mongod command using the command-line terminal:

And then we open another terminal to open the server for the no-SQL transactions through the mongo command: