Embedded servlet containers
73. Embedded servlet containers
There are two ways to add Servlet, Filter, ServletContextListener and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them, or enable scanning for Servlet components.
To add a Servlet, Filter, or Servlet *Listener provide a @Bean definition for it. This can be very useful when you want to inject configuration or dependencies. However, you must be very careful that they don’t cause eager initialization of too many other beans because they have to be installed in the container very early in the application lifecycle (e.g. it’s not a good idea to have them depend on your DataSource or JPA configuration). You can work around restrictions like that by initializing them lazily when first used instead of on initialization.
In the case of Filters and Servlets you can also add mappings and init parameters by adding a FilterRegistrationBean or ServletRegistrationBeaninstead of or as well as the underlying component.
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If no If you are migrating a filter that has no @Bean public FilterRegistrationBean myFilterRegistration() { FilterRegistrationBean registration = new FilterRegistrationBean(); registration.setDispatcherTypes(DispatcherType.REQUEST); .... return registration; } |
As described above any Servlet or Filter beans will be registered with the servlet container automatically. To disable registration of a particular Filter or Servlet bean create a registration bean for it and mark it as disabled. For example:
@Bean public FilterRegistrationBean registration(MyFilter filter) { FilterRegistrationBean registration = new FilterRegistrationBean(filter); registration.setEnabled(false); return registration; }
@WebServlet, @WebFilter, and @WebListener annotated classes can be automatically registered with an embedded servlet container by annotating a @Configuration class with @ServletComponentScan and specifying the package(s) containing the components that you want to register. By default, @ServletComponentScan will scan from the package of the annotated class.
In a standalone application the main HTTP port defaults to 8080, but can be set with server.port (e.g. in application.properties or as a System property). Thanks to relaxed binding of Environment values you can also use SERVER_PORT (e.g. as an OS environment variable).
To switch off the HTTP endpoints completely, but still create a WebApplicationContext, use server.port=-1 (this is sometimes useful for testing).
For more details look at Section 27.3.4, “Customizing embedded servlet containers” in the ‘Spring Boot features’ section, or the ServerProperties source code.
To scan for a free port (using OS natives to prevent clashes) use server.port=0.
You can access the port the server is running on from log output or from the EmbeddedWebApplicationContext via its EmbeddedServletContainer. The best way to get that and be sure that it has initialized is to add a @Bean of type ApplicationListener<EmbeddedServletContainerInitializedEvent> and pull the container out of the event when it is published.
Tests that use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) can also inject the actual port into a field using the @LocalServerPortannotation. For example:
@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) public class MyWebIntegrationTests { @Autowired EmbeddedWebApplicationContext server; @LocalServerPort int port; // ... }
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SSL can be configured declaratively by setting the various server.ssl.* properties, typically in application.properties or application.yml. For example:
server.port=8443
server.ssl.key-store=classpath:keystore.jks
server.ssl.key-store-password=secret
server.ssl.key-password=another-secret
See Ssl for details of all of the supported properties.
Using configuration like the example above means the application will no longer support plain HTTP connector at port 8080. Spring Boot doesn’t support the configuration of both an HTTP connector and an HTTPS connector via application.properties. If you want to have both then you’ll need to configure one of them programmatically. It’s recommended to use application.properties to configure HTTPS as the HTTP connector is the easier of the two to configure programmatically. See the spring-boot-sample-tomcat-multi-connectors sample project for an example.
Access logs can be configured for Tomcat and Undertow via their respective namespaces.
For instance, the following logs access on Tomcat with a custom pattern.
server.tomcat.basedir=my-tomcat
server.tomcat.accesslog.enabled=true
server.tomcat.accesslog.pattern=%t %a "%r" %s (%D ms)
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The default location for logs is a |
Access logging for undertow can be configured in a similar fashion
server.undertow.accesslog.enabled=true
server.undertow.accesslog.pattern=%t %a "%r" %s (%D ms)
Logs are stored in a logs directory relative to the working directory of the application. This can be customized via server.undertow.accesslog.directory.
Your application might need to send 302 redirects or render content with absolute links back to itself. When running behind a proxy, the caller wants a link to the proxy, and not to the physical address of the machine hosting your app. Typically such situations are handled via a contract with the proxy, which will add headers to tell the back end how to construct links to itself.
If the proxy adds conventional X-Forwarded-For and X-Forwarded-Proto headers (most do this out of the box) the absolute links should be rendered correctly as long as server.use-forward-headers is set to true in your application.properties.
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If your application is running in Cloud Foundry or Heroku the |
If you are using Tomcat you can additionally configure the names of the headers used to carry “forwarded” information:
server.tomcat.remote-ip-header=x-your-remote-ip-header server.tomcat.protocol-header=x-your-protocol-header
Tomcat is also configured with a default regular expression that matches internal proxies that are to be trusted. By default, IP addresses in 10/8, 192.168/16,169.254/16 and 127/8 are trusted. You can customize the valve’s configuration by adding an entry to application.properties, e.g.
server.tomcat.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}
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The double backslashes are only required when you’re using a properties file for configuration. If you are using YAML, single backslashes are sufficient and a value that’s equivalent to the one shown above would be |
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You can trust all proxies by setting the |
You can take complete control of the configuration of Tomcat’s RemoteIpValve by switching the automatic one off (i.e. set server.use-forward-headers=false) and adding a new valve instance in a TomcatEmbeddedServletContainerFactory bean.
Generally you can follow the advice from Section 72.8, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties is the main one here), but also look at EmbeddedServletContainerCustomizer and various Tomcat-specific *Customizers that you can add in one of those. The Tomcat APIs are quite rich so once you have access to the TomcatEmbeddedServletContainerFactory you can modify it in a number of ways. Or the nuclear option is to add your own TomcatEmbeddedServletContainerFactory.
Add a org.apache.catalina.connector.Connector to the TomcatEmbeddedServletContainerFactory which can allow multiple connectors, e.g. HTTP and HTTPS connector:
@Bean public EmbeddedServletContainerFactory servletContainer() { TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory(); tomcat.addAdditionalTomcatConnectors(createSslConnector()); return tomcat; } private Connector createSslConnector() { Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol"); Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler(); try { File keystore = new ClassPathResource("keystore").getFile(); File truststore = new ClassPathResource("keystore").getFile(); connector.setScheme("https"); connector.setSecure(true); connector.setPort(8443); protocol.setSSLEnabled(true); protocol.setKeystoreFile(keystore.getAbsolutePath()); protocol.setKeystorePass("changeit"); protocol.setTruststoreFile(truststore.getAbsolutePath()); protocol.setTruststorePass("changeit"); protocol.setKeyAlias("apitester"); return connector; } catch (IOException ex) { throw new IllegalStateException("can't access keystore: [" + "keystore" + "] or truststore: [" + "keystore" + "]", ex); } }
The embedded Tomcat used by Spring Boot does not support "Version 0" of the Cookie format out of the box, and you may see the following error:
java.lang.IllegalArgumentException: An invalid character [32] was present in the Cookie value
If at all possible, you should consider updating your code to only store values compliant with later Cookie specifications. If, however, you’re unable to change the way that cookies are written, you can instead configure Tomcat to use a LegacyCookieProcessor. To switch to the LegacyCookieProcessor use anEmbeddedServletContainerCustomizer bean that adds a TomcatContextCustomizer:
@Bean public EmbeddedServletContainerCustomizer cookieProcessorCustomizer() { return new EmbeddedServletContainerCustomizer() { @Override public void customize(ConfigurableEmbeddedServletContainer container) { if (container instanceof TomcatEmbeddedServletContainerFactory) { ((TomcatEmbeddedServletContainerFactory) container) .addContextCustomizers(new TomcatContextCustomizer() { @Override public void customize(Context context) { context.setCookieProcessor(new LegacyCookieProcessor()); } }); } } }; }
The Spring Boot starters (spring-boot-starter-web in particular) use Tomcat as an embedded container by default. You need to exclude those dependencies and include the Jetty one instead. Spring Boot provides Tomcat and Jetty dependencies bundled together as separate starters to help make this process as easy as possible.
Example in Maven:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> </dependency>
Example in Gradle:
configurations {
compile.exclude module: "spring-boot-starter-tomcat"
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web:1.5.3.RELEASE")
compile("org.springframework.boot:spring-boot-starter-jetty:1.5.3.RELEASE")
// ...
}
Generally you can follow the advice from Section 72.8, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties is the main one here), but also look at EmbeddedServletContainerCustomizer. The Jetty APIs are quite rich so once you have access to the JettyEmbeddedServletContainerFactory you can modify it in a number of ways. Or the nuclear option is to add your own JettyEmbeddedServletContainerFactory.
Using Undertow instead of Tomcat is very similar to using Jetty instead of Tomcat. You need to exclude the Tomcat dependencies and include the Undertow starter instead.
Example in Maven:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-undertow</artifactId> </dependency>
Example in Gradle:
configurations {
compile.exclude module: "spring-boot-starter-tomcat"
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web:1.5.3.RELEASE")
compile("org.springframework.boot:spring-boot-starter-undertow:1.5.3.RELEASE")
// ...
}
Generally you can follow the advice from Section 72.8, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties and ServerProperties.Undertow are the main ones here), but also look at EmbeddedServletContainerCustomizer. Once you have access to theUndertowEmbeddedServletContainerFactory you can use an UndertowBuilderCustomizer to modify Undertow’s configuration to meet your needs. Or the nuclear option is to add your own UndertowEmbeddedServletContainerFactory.
Add an UndertowBuilderCustomizer to the UndertowEmbeddedServletContainerFactory and add a listener to the Builder:
@Bean public UndertowEmbeddedServletContainerFactory embeddedServletContainerFactory() { UndertowEmbeddedServletContainerFactory factory = new UndertowEmbeddedServletContainerFactory(); factory.addBuilderCustomizers(new UndertowBuilderCustomizer() { @Override public void customize(Builder builder) { builder.addHttpListener(8080, "0.0.0.0"); } }); return factory; }
Tomcat 7 & 8.0 work with Spring Boot, but the default is to use Tomcat 8.5. If you cannot use Tomcat 8.5 (for example, because you are using Java 1.6) you will need to change your classpath to reference a different version.
If you are using the starters and parent you can change the Tomcat version property and additionally import tomcat-juli. E.g. for a simple webapp or service:
<properties> <tomcat.version>7.0.59</tomcat.version> </properties> <dependencies> ... <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.apache.tomcat</groupId> <artifactId>tomcat-juli</artifactId> <version>${tomcat.version}</version> </dependency> ... </dependencies>
With Gradle, you can change the Tomcat version by setting the tomcat.version property and then additionally include tomcat-juli:
ext['tomcat.version'] = '7.0.59'
dependencies {
compile 'org.springframework.boot:spring-boot-starter-web'
compile group:'org.apache.tomcat', name:'tomcat-juli', version:property('tomcat.version')
}
Jetty 9.2 works with Spring Boot, but the default is to use Jetty 9.3. If you cannot use Jetty 9.3 (for example, because you are using Java 7) you will need to change your classpath to reference Jetty 9.2.
If you are using the starters and parent you can just add the Jetty starter and override the jetty.version property:
<properties> <jetty.version>9.2.17.v20160517</jetty.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> </dependency> </dependencies>
You can set the jetty.version property. For example, for a simple webapp or service:
ext['jetty.version'] = '9.2.17.v20160517'
dependencies {
compile ('org.springframework.boot:spring-boot-starter-web') {
exclude group: 'org.springframework.boot', module: 'spring-boot-starter-tomcat'
}
compile ('org.springframework.boot:spring-boot-starter-jetty')
}
Jetty 8 works with Spring Boot, but the default is to use Jetty 9.3. If you cannot use Jetty 9.3 (for example, because you are using Java 1.6) you will need to change your classpath to reference Jetty 8. You will also need to exclude Jetty’s WebSocket-related dependencies.
If you are using the starters and parent you can just add the Jetty starter with the required WebSocket exclusion and change the version properties, e.g. for a simple webapp or service:
<properties> <jetty.version>8.1.15.v20140411</jetty.version> <jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> <exclusions> <exclusion> <groupId>org.eclipse.jetty.websocket</groupId> <artifactId>*</artifactId> </exclusion> </exclusions> </dependency> </dependencies>
You can set the jetty.version property and exclude the WebSocket dependency, e.g. for a simple webapp or service:
ext['jetty.version'] = '8.1.15.v20140411'
dependencies {
compile ('org.springframework.boot:spring-boot-starter-web') {
exclude group: 'org.springframework.boot', module: 'spring-boot-starter-tomcat'
}
compile ('org.springframework.boot:spring-boot-starter-jetty') {
exclude group: 'org.eclipse.jetty.websocket'
}
}
If you want to use @ServerEndpoint in a Spring Boot application that used an embedded container, you must declare a single ServerEndpointExporter @Bean:
@Bean public ServerEndpointExporter serverEndpointExporter() { return new ServerEndpointExporter(); }
This bean will register any @ServerEndpoint annotated beans with the underlying WebSocket container. When deployed to a standalone servlet container this role is performed by a servlet container initializer and the ServerEndpointExporter bean is not required.
HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled via application.properties:
server.compression.enabled=true
By default, responses must be at least 2048 bytes in length for compression to be performed. This can be configured using the server.compression.min-response-size property.
By default, responses will only be compressed if their content type is one of the following:
text/htmltext/xmltext/plaintext/css
This can be configured using the server.compression.mime-types property.
https://docs.spring.io/spring-boot/docs/current/reference/html/howto-embedded-servlet-containers.html#howto-embedded-servlet-containers
