Spring Boot in the Web Tier

This presentation shows you how to understand and harness those features for maximum benefit. We will cover the basics of opinionated application configuration, showing what Spring Boot has to offer the web developer out of the box: content negotiation, internationalization, view templates, security, messaging with websockets, etc. We will look at the embedded servlet container abstractions in Spring Boot, showing how to customize the containers, and how to extract the most from the containers at runtime. We will also show how Spring Boot can embed some other interesting and popular web technologies, like Jersey and Ratpack, giving developers instant access to a wide range of useful features, and zero-effort integration with the Spring for middleware integration.

Transcript

1. Spring Boot for the Web Tier
   Phillip Webb
   twiiter: @phillip_webb
   email: pwebb@pivotal.io
   Dave Syer
   twitter: @david_syer
   email: dsyer@pivotal.io
   http://localhost:4000/decks/spring-boot-for-the-web-tier.html
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2. Presentation Overview
   Part 1 - Static Content
   Part 2 - Dynamic Content
   Part 3 - Embedded Server
   Part 4 - Other Stacks
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3. Static Content - Serving Files
   Can't use /src/main/webapp for jar deployments
   Put static files from src/main/resources/static
   or .../public or .../resources or .../META-
   INF/resources
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4. Static Content - Conventions
   src/main/resources/static/index.html is mapped to
   /index.html & /
   Add a src/main/resources/favicon.ico to replace the Spring
   Leaf
   Imported "webjars" are automatically mapped
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5. Demo - Static Content
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6. Static Content: Grunt
   Toolchain
   For serious front end developers the best choice is a Javascript toolchain.
   Good community, lots of tools
   Package static assets into a jar
   And/or build them as part of a very thin back end
   Spring Boot CLI makes a great lightweight back end in production or
   for Java devs
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7. Static Content - wro4j
   Great for Java developers
   Often good enough
   JsHint
   CssLint
   JsMin
   Google Closure compressor
   UglifyJs
   Less
   Sass
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8. Static Content - Wro4j with
   Maven
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9. 
   ro.isdc.wro4j
   wro4j-maven-plugin
   ${wro4j.version}
   
   generate-resources
   run
   
   
   ro.isdc.wro.maven.plugin.manager.factory.Configu
   rableWroManagerFactory
   ${basedir}/target/generated-resources
   /static/
   ${basedir}/src/main/wro/wro.xml
   ${basedir}/src/main/wro
   /wro.properties
   
   
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10. Static Content - Wro4j with
    Maven
    src/main/wro/wro.xml
    
    
    file:./src/main/wro/main.less
    
    
    src/main/wro/wro.properties
    postProcessors=less4j
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11. Dynamic Content - Templating
    Support
    Thymeleaf
    Groovy Template Language
    Freemarker
    Velocity
    JSP (not recommended)
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12. Dynamic Content - Template
    Conventions
    Templates live in src/main/resources/templates
    and are accessed via classpath:/templates/
    Default Extensions are:
    *.html - Thymeleaf
    *.tpl - Groovy
    *.ftl - Freemarker
    *.vm - Velocity
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13. Dynamic Content - Template
    Customization
    User spring.xxx.prefix and spring.xxx.suffix
    eg. spring.freemarker.suffix=fm
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14. Demo - Templatinghttp://localhost:4000/decks/spring-boot-for-the-web-tier.html
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15. Dynamic Content - Custom
    Support
    Add a ViewResolver
    Optionally add a TemplateAvailabilityProvider
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16. public class GroovyTemplateAvailabilityProvider implements
    TemplateAvailabilityProvider {
    @Override
    public boolean isTemplateAvailable(String view, Environment
    environment,
    ClassLoader classLoader, ResourceLoader resourceLoader) {
    if (ClassUtils.isPresent("groovy.text.TemplateEngine",
    classLoader)) {
    String prefix =
    environment.getProperty("spring.groovy.template.prefix",
    GroovyTemplateProperties.DEFAULT_PREFIX);
    String suffix =
    environment.getProperty("spring.groovy.template.suffix",
    GroovyTemplateProperties.DEFAULT_SUFFIX);
    return resourceLoader.getResource(prefix + view +
    suffix).exists();
    }
    return false;
    }
    }
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17. Dynamic Content -
    Internationalization
    A MessageSource bean is added when src/main/resources
    /messages.properties exists
    Use messages_LOCALE.properties to add additional locales
    e.g. messages_FR.properties
    Choose a specific locale using the spring.mvc.locale property
    Choose a specific date format using the spring.mvc.date-
    format property
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18. Dynamic Content -
    HttpMessageConverter
    Add HttpMessageConverter beans and Spring Boot will try to do
    the right thing
    It tries to be intelligent about the order
    Add a HttpMessageConverters bean if you need more control
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19. Dynamic Content - Rest
    Use the @RestContoller annotation
    Use ResponseEntity builder methods with Spring Framework 4.1
    ResponseEntity.
    accepted().
    contentLength(3).
    contentType(MediaType.TEXT_PLAIN).
    body("Yo!");
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20. Demo - HttpMessageConverter
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21. Dynamic Content - Hidden
    Gems
    You can get the RequestContext from RequestContextHolder
    anywhere
    The request has some useful things in it (from Spring), e.g.
    HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE
    All Converter, Formatter, GenericConverter beans are
    automatically added
    Use spring.mvc.message-codes-resolver-format to add a
    MessageCodesResolver
    prefix_error_code or postfix_error_code
    # prefix_error_code
    empty.customer.name=Customer name is required
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22. # postfix_error_code
    customer.name.empty=Customer name is required
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23. Embedded Server
    When using WARs a ServletContainerInitializer creates
    the Spring ApplicationContext
    When running embedded the ApplicationContext creates the
    Server
    Expects a single EmbeddedServletContainerFactory bean
    Odd dance for
    WebApplicationContext.getServletContext() and
    ServletConfigAware
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24. Embedded Server -
    Initialization
    The following beans are used to configure the server:
    Servlet
    Filter
    ServletRequestListener
    ServletRequestAttributeListener
    HttpSessionAttributeListener
    HttpSessionListener
    ServletContextListener
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25. Embedded Server -
    Initialization
    For more control use
    ServletRegistrationBean
    FilterRegistrationBean
    ServletListenerRegistrationBean
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26. @Bean
    public ServletRegistrationBean myServlet() {
    ServletRegistrationBean bean =
    new ServletRegistrationBean(new MyServlet(), "/mine");
    bean.setAsyncSupported(false);
    bean.setInitParameters(Collections.singletonMap("debug",
    "true"));
    return bean;
    }
    @Bean
    public FilterRegistrationBean myFilter() {
    return new FilterRegistrationBean(new MyFilter(), myServlet());
    }
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27. Embedded Server -
    Initialization
    By design the following are not called with embedded servers:
    javax.servlet.ServletContainerInitializer
    org.springframework.web.WebApplicationInitializer
    Use
    o.s.boot.context.embedded.ServletContextInitializer
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28. /**
    * Configure the given {@link ServletContext} with any servlets,
    filters, listeners
    * context-params and attributes necessary for initialization.
    * @param servletContext the {@code ServletContext} to initialize
    * @throws ServletException if any call against the given {@code
    ServletContext}
    * throws a {@code ServletException}
    */
    void onStartup(ServletContext servletContext) throws
    ServletException;
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29. Embedded Server -
    Customization
    Use ServerProperties (e.g. server.port=8080)
    EmbeddedServletContainerCustomizer
    Customize common things (e.g. the port, error-pages,
    context-path)
    Tomcat Specific
    TomcatConnectorCustomizer
    TomcatContextCustomizer
    Jetty Specific
    JettyServerCustomizer
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30. Embedded Server -
    Customization
    If all else fails subclass EmbeddedServletContainerFactory
    Lots of protected methods to override
    TomcatEmbeddedServletContainerFactory
    JettyEmbeddedServletContainerFactory
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31. @Bean
    public TomcatEmbeddedServletContainerFactory tomcatFactory() {
    return new TomcatEmbeddedServletContainerFactory(7070) {
    @Override
    protected void customizeConnector(Connector connector) {
    // Something with the connector
    }
    @Override
    protected void configureSsl(AbstractHttp11JsseProtocol>
    protocol, Ssl ssl) {
    // Something with ssl
    }
    };
    }
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32. Embedded Server - Tomcat
    Behind HTTPD
    Running behind Apache HTTPD is a common option
    Especially useful with SSL termination
    Real IP and SSL information is passed in headers
    server.tomcat.protocol-header=x-forwarded-proto
    server.tomcat.remote-ip-header=x-forwarded-for
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33. Embedded Server - Tomcat
    Behind HTTPD
    
    ServerName example.spring.io
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
    ProxyPass / http://${TOMCAT_IP}:8080/
    ProxyPassReverse / http://${TOMCAT_IP}:8080/
    
    
    SSLEngine on
    SSLCertificateFile /etc/apache2/ssl/apache.crt
    SSLCertificateKeyFile /etc/apache2/ssl/apache.key
    ProxyPass / http://${TOMCAT_IP}:8080/
    ProxyPassReverse / http://${TOMCAT_IP}:8080/
    RequestHeader set X-Forwarded-Proto "https"
    RequestHeader set X-Forwarded-Port "443"
    
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34. Demo - Running Behind
    HTTPS
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35. Other Stacks
    JAX-RS: Jersey 1.x, Jersey 2.x dsyer/spring-boot-jersey, CXF
    (allegedly works)
    Netty and NIO: Ratpack dsyer/spring-boot-ratpack
    Servlet 2.5 scratches/spring-boot-legacy
    Vaadin peholmst/vaadin4spring
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36. Jersey 1.x
    Easy to integrate with Spring Boot using Filter (or Servlet), e.g.
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37. @Configuration
    @EnableAutoConfiguration
    @Path("/")
    public class Application {
    @GET
    @Produces("text/plain")
    public String hello() {
    return "Hello World";
    }
    @Bean
    public FilterRegistrationBean jersey() {
    FilterRegistrationBean bean = new FilterRegistrationBean();
    bean.setFilter(new ServletContainer());
    bean.addInitParameter("com.sun.jersey.config.property.packages",
    "com.mycompany.myapp");
    return bean;
    }
    }
    (N.B. with fat jar you need to explicitly list the nested jars that have
    JAX-RS resources in them.)
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38. Jersey 2.x
    Spring integration is provided out of the box, but a little bit tricky to use
    with Spring Boot, so some autoconfiguration is useful. Example app:
    @Configuration
    @Path("/")
    public class Application extends ResourceConfig {
    @GET
    public String message() {
    return "Hello";
    }
    public Application() {
    register(Application.class);
    }
    }
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39. Ratpack
    Originally inspired by Sinatra, but now pretty much diverged. Provides a
    nice programming model on top of Netty (potentially taking advantage of
    non-blocking IO).
    2 approaches:
    Ratpack embeds Spring (and uses it as a Registry), supported
    natively in Ratpack 0.9.9
    Spring embeds Ratpack (and uses it as an HTTP listener) = spring-
    boot-ratpack
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40. Spring Boot embedding
    Ratpack
    Trivial example (single Handler):
    @Bean
    public Handler handler() {
    return (context) -> {
    context.render("Hello World");
    };
    }
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41. Spring Boot embedding
    Ratpack
    More interesting example (Action registers Handlers):
    @Bean
    public Handler hello() {
    return (context) -> {
    context.render("Hello World");
    };
    }
    @Bean
    public Action handlers() {
    return (chain) -> {
    chain.get(hello());
    };
    }
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42. Spring Boot Ratpack DSL
    A valid Ratpack Groovy application:
    ratpack {
    handlers {
    get {
    render "Hello World"
    }
    }
    }
    launched with Spring Boot:
    $ spring run app.groovy
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43. Questions?
    http://projects.spring.io/spring-boot/
    https://github.com/SpringOne2GX-2014/spring-boot-for-the-web-tier
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