The new Technology Radar is here!

25 01 2015

The new Technology Radar is realeased: My impressions are:

Languages an Frameworks

– ‘Adopt’ Java 8,

AngularJS in its ‘trial’, encouraging you to use it

– Spring Boot after a year of official release in the ‘assess’ phase – its maturity still waiting to be confirmed

– on the contrary – JSF in a hold phase


Microservices assessment (HOLD) is very interesting:

“We remain convinced that microservices can offer significant advantages to organizations, in terms of improving team autonomy and faster frequency of change. The additional complexity that comes from distributed systems requires an additional level of maturity and investment. We are concerned that some teams are rushing in to adopting microservices without understanding the changes to development, test, and operations that are required to do them well. Our general advice remains simple. Avoidmicroservice envy and start with one or two services before rushing headlong into developing more, to allow your teams time to adjust and understand the right level of granularity.”

I tend to agree with all statements, regarding my experience with microservices, but ‘hold’ phase is a little bit to stringent.

HTML 5 Offline Web Application with Spring Boot

30 11 2014

Think of users using your web application from mobile phones when their internet connection breaks down. Native mobile app would still work and cache all user actions, synchronizing them afterwards. HTML5 web apps can also work offline.

Basically it is done by listing the resource files (html, js, images) that browser should cache immadietly and use the cached version when user redirects to it. If internet connection is working, the browser will return the online server version, else, if user is offline the cached version will be used.

Resources to cache can be defined in html headers or in .manifest file. These two locations are interpreted by all modern browsers.

1. Download the code base

This tutorial is based on the source code from SpringBoot MVC Hello World tutorial. All instructions are performed on this code.

2. Create offline.manifest file

In this file you can select the files and resources that will be cached by the browser and used if user requests to connect with server while being disconnected from the Internet. I will create new html file: offline.html and redirect to it if user is offline. My offline.manifest looks as follows:




/ /offline.html

And is located under the /src/main/resources/static/offline.manifest.

3. Manifest file explained

The manifest file must begin with CACHE MANIFEST. The CACHE: section lists the files that we need for offline use. The NETWORK: section lists any resources that should not be cached. The FALLBACK: section uses the / character to define a URL pattern. It basically asks “is this page in the cache?” If it finds the page there, it displays it. If not, it shows the user the file specified – offline.html.

4. Create the offline.html page

This page will be displayed when user requests any page while being offline. This is static page – not the Spring template, so i simply put it in the /src/main/resources/static folder, next to the offfline.manifest file. The offline.html page content is basic one:

<!DOCTYPE html>
<html xmlns="" 
  xmlns:th="" >
        <title>Offline Web Application</title>
        <h1>You are offline</h1>

5. Request to cache resources

To make use of offline.manifest file I point it in my hello.html and greeting.html page head:

<html xmlns="" 

This way the browser will download the manifest and cache specified resources. Moreover it will add the hello.html and greeting.html to the cache as well

6. Test it

Run spring boot app, and open the url in the browser. When you are on hello page, the browser will cache files for offline use. In Chrome console this is indicated as:

hello:1 Creating Application Cache with manifest http://localhost:8080/offline.manifest
hello:1 Application Cache Checking event
hello:1 Application Cache Downloading event
hello:1 Application Cache Progress event (0 of 1) http://localhost:8080/offline.html
hello:1 Application Cache Progress event (1 of 1) 
hello:1 Application Cache Cached event

Now stop the Spring Boot app and click the url on th page. Since the server is offline, you will be redirected to cached offline.html page (or the greeting.html if it was previously cached). If you try tu go to any other url, for example: http://localhost:8080/someInvalidUrl – then the offline html page will be displayed.

Note: best to be tested in private / incognito browser mode to prevent unwanted cache.

Get the source Code

Full source code for this tutorial you can get at my GitHub under the SpringBootOfflineWebApp tag:

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Spring Boot: SSL/HTTPS for embedded Tomcat

22 11 2014

If your Spring Boot app is running on embedded Tomcat, you need to use the TomcatConnectionCustomizer class to set up the HTTPS in Tomcat.

Get the source code

Source Code for this tutorial is available on my github under the SpringBootHttps tag:

1. Prepare keystore and certificate

First you need to have your certificate. If you already have it, go to point 2., else, follow the step 1 and 2 from this tutorial:

2. Put your keystore in defined location

You need to locate your keystore file in path on your machine. On my machine this is:


This path I will use in my app configuration.

3. Customize Tomcat Connection

Create class implementing the TomcatConnectorCustomizer, and override its customize(Connection) method. As you can see, in customize() I set exactly the same properties as in stantalone Tomcat xml configuration (see this post). Note that in class constructor I convert the alias string to lowercase – in keystore only these are allowed.

public class MyTomcatConnectionCustomizer implements TomcatConnectorCustomizer {

  private String absoluteKeystoreFile;
  private String keystorePassword;
  private String keystoreType;
  private String keystoreAlias;

  public MyTomcatConnectionCustomizer(String absoluteKeystoreFile,
      String keystorePassword, String keystoreType, String keystoreAlias) {
    this.absoluteKeystoreFile = absoluteKeystoreFile;
    this.keystorePassword = keystorePassword;
    this.keystoreType = keystoreType;
    this.keystoreAlias = keystoreAlias.toLowerCase();


  public void customize(Connector connector) {
    connector.setAttribute("SSLEnabled", true);
        connector.setAttribute("sslProtocol", "TLS");
        connector.setAttribute("protocol", "org.apache.coyote.http11.Http11Protocol");
        connector.setAttribute("clientAuth", false);
        connector.setAttribute("keystoreFile", absoluteKeystoreFile);
        connector.setAttribute("keystoreType", keystoreType);
        connector.setAttribute("keystorePass", keystorePassword);
        connector.setAttribute("keystoreAlias", keystoreAlias);
        connector.setAttribute("keyPass", keystorePassword);

4. Create containerCustomizer Bean

Now to use the TomcatConnectionCustomizer, create the bean as follows:

public EmbeddedServletContainerCustomizer containerCustomizer() throws FileNotFoundException {

  final String absoluteKeystoreFile = ResourceUtils.getFile("D:\\keystore\\server.p12").getAbsolutePath();

  final TomcatConnectorCustomizer customizer = new MyTomcatConnectionCustomizer(
      absoluteKeystoreFile, "keyPwd", "PKCS12", "keyalias"); 

  return new EmbeddedServletContainerCustomizer() {

    public void customize(ConfigurableEmbeddedServletContainer container) {
      if(container instanceof TomcatEmbeddedServletContainerFactory) {
        TomcatEmbeddedServletContainerFactory containerFactory = (TomcatEmbeddedServletContainerFactory) container;

5. Test it

Start Spring Boot App and go to the:


Your browser will propably warn you about the untrusted certificate:


Note: Don’t use Self_signed certificates in production! Use it only in test / dev environment

Get the source code

Source Code for this tutorial is available on my github under the SpringBootHttps tag:

Did I help you?
I manage this blog and share my knowledge for free, sacrificing my time. If you appreciate it and find this information helpful, please consider making a donation in order to keep this page alive and improve quality

Donate Button with Credit Cards

Thank You!

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