Spring 4 advanced final_xtr_presentation

By : Sourabh Aggarwal
Date : 08 OCT 2015
SPRING 4 ++
(ADVANCED)

Cache Improvements in 4.1
● Spring’s caching abstraction is available as from Spring 3.1.
Now we have JCache (JSR-107) annotations support.
● The following table describes the mapping between the Spring
annotations and the JSR-107 counterpart.
SPRING JSR-107
@Cacheable @CacheResult
@CachePut @CachePut
@CacheEvict @CacheRemove
@CacheEvict(allEntries=true) @CacheRemoveAll

@CacheResult
● @CacheResult is fairly similar to @Cacheable, the following rewrites the original example using
the @CacheResult annotation.
● Code rewrite:
@CacheResult(cacheName = "books")
public Employee findEmployee(String employeeID) {...}
● Keys generation can be customized using the CacheKeyGenerator interface. If no specific
implementation is specified, the default implementation, per spec, takes all parameters unless
one or more parameters are annotated with the @CacheKey annotation, in which case only
those are used. Assuming that the method above needs now an extra attribute that should not
be part of the key, this is how we would write it with Jcache.
● Code rewrite:
@CacheResult(cacheName = "book")
public Employee findEmployee(@CacheKey String employeeID, boolean stillThere) { ... }

Caching Exception
● @CacheResult brings the concept of exception cache: whenever a method execution
failed, it is possible to cache the exception that was raised to prevent calling the
method again. Let’s assume that InvalidIsbnNotFoundException is thrown if the
structure of the employeeID is invalid. This is a permanent failure, no book could ever
be retrieved with such parameter. The following caches the exception so that further
calls with the same, invalid employeeID, throws the cached exception directly instead
of invoking the method again..
● Code rewrite:
@CacheResult(cacheName = "Employees", exceptionCacheName = "failures"
cachedExceptions = InvalidIdNotFoundException.class)
public Employee findEmployee(@CacheKey String employeeID) { ... }

CacheResolverFactory
● JCache has this cool notion of CacheResolver that permits to resolve the cache to use at
runtime. Because JCache supports regular caches and exception caches, the CacheResolver
instances to use are determined by a CacheResolverFactory. The obvious default is to resolve
the cache to use based on the cacheName and exceptionCacheName attributes, respectively.
However, it is also possible to customize the factory to use per operation.
● Code rewrite:
@CacheResult(cacheName = "Employees", cacheResolverFactory = MyFactory.class)
public Employee findEmployee(@CacheKey String employeeID) { ... }
● Finally, @CacheResult has a skipGet attribute that can be enabled to always invoke the method
regardless of the status of the cache. This is actually quite similar to our own use of @CachePut.

@CachePut
●
While the annotations have the same name, the semantic in JCache is fairly different. A simple update
for our employee would be written like this.
● Code rewrite:
@CachePut(value = "Employees", key = "#p0")
public Employee update(String employeeId, Employee updatedEmployee) { ... }
● While JCache would require you to write it like this.
●
Code rewrite:
@CachePut(cacheName = "Employees")
public void update(String employeeId, @CacheValue Employee updatedEmployee) { ... }
●
Note that even though updatedEmployee should not be part of the key, we didn’t have to add a
@CacheKey to the first argument. This is because the parameter annotated with @CacheValue is
automatically excluded from the key generation.
●
As for @CacheResult, @CachePut allows to manage any exception that is thrown while executing the
method, preventing the put operation to happen if the thrown exception matches the filter specified on
the annotation.

@CacheRemove and
@CacheRemoveAll
● These are really similar to @CacheEvict and
@CacheEvict(allEntries = true) respectively. @CacheRemove
has a special exception handling to prevent the eviction if the
annotated method throws an exception that matches the filter
specified on the annotation.

@CacheDefaults
● @CacheDefaults is a class-level annotation that allows you to share common
settings on any caching operation defined on the class. These are:
– The name of the cache
– The custom CacheResolverFactory
– The custom CacheKeyGenerator
● Code rewrite:
@CacheDefaults(cacheName = "Employees")
public class EmployeeRepositoryImpl implements EmployeeRepository {
@CacheResult
public Employee findEmployee(@CacheKey String employeeId) { ... }
}

Enabling JSR-107 support
– The implementation of the JCache support uses our own Cache and CacheManager
abstraction which means that you can use your existing CacheManager infrastructure,
and yet use standard annotations!
– To enable the support of Spring caching annotations, you are used to either
@EnableCaching or the <cache:annotation-driven/> xml element, for instance something
like:
@Configuration
@EnableCaching
public class AppConfig {
@Bean
public CacheManager cacheManager() { ...}
}
– So, what does it take to bring the support of standard annotations into the mix? Well, not
much. Just add the JCache API and the spring-context-support module in your classpath
if you haven’t already and you’ll be set.

– @Cachable is used to so that the Employees are cached within the Employees cache.
@Component
public class SimpleEmployeeRepository implements EmployeeRepository {
long time = 5000L;
private void simulateSlowService() {
try {
Thread.sleep(time);
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
}
@Cacheable("Employees")
public Employee getByEmployeeId(String employeeId) {
simulateSlowService();
return new Employee("ABCD", "XI265");
}
public Employee getByEmployeeIdWithoutCaching(String employeeId) {
simulateSlowService();
return new Employee("FGHJ", "XI789");
}
}

– Output cachable object :
2015-10-07 15:56:47:::::::::::: XI265 -->Employee{name='ABCD',
employeeId='XI265'}
employeeId='XI265'}
employeeId='XI265'}
– Output non cachable object :
2015-10-07 15:57:24:::::::::::: XI789 -->Employee{name='FGHJ',
employeeId='XI789'}
employeeId='XI789'}
employeeId='XI789'}

Caching support
l
Hands on!!!!

New modules added
– Spring-websocket :
● Helps the two way communication between client and server.
● WebSocket-style messaging in web applications including use of STOMP as an
application level WebSocket sub-protocol.
● SockJS Fallback Options” explains the SockJS protocol and shows how to configure and
use it.
● Module is added in Spring 4.0 not present in previous versions.
– Spring-messaging :
● The module includes a set of annotations for mapping messages to methods, similar to
the Spring MVC annotation based programming model.
● Spring Framework 4 includes a new spring-messaging module with key abstractions from
the Spring Integration project such as Message, MessageChannel, MessageHandler, and
others that can serve as a foundation for such a messaging architecture.
● Module is added in Spring 4.0 not present in previous versions.

Web-Socket Module
– WebSocket is a very thin, lightweight layer above TCP.
– It makes it very suitable to use "subprotocols" to embed messages.
– In example we’ll dive in and use STOMP(Simple or Streaming Text
Oriented Message Protocol) messaging with Spring to create an
interactive web application.
– STOMP, formerly known as TTMP, is a simple text-based protocol,
designed for working with message-oriented middleware (MOM).
– Example that sends messages back and forth, between a browser and
the server.

STOMP(Streaming Text Oriented
Message Protocol)
The protocol is broadly similar to HTTP, and works over TCP using the following commands:
•
CONNECT
•
SEND
•
SUBSCRIBE
•
UNSUBSCRIBE
•
BEGIN
• COMMIT
•
ABORT
•
ACK
•
NACK
•
DISCONNECT
Communication between client and server is through a "frame" consisting of a number of lines.
The first line contains the command, followed by headers in the form <key>: <value> (one per
line), followed by a blank line and then the body content, ending in a null character.
Communication between server and client is through a MESSAGE, RECEIPT or ERROR frame
with a similar format of headers and body content.

Example.......
●
We’ll build a server that will accept a message carrying a user’s name. In
response, it will push a greeting into a queue that the client is subscribed to.
●
STOMP message for name sourabh
{"name": "sourabh"}.
●
Message carrying the name, you can create a plain old Java object with a
name property and a corresponding getName() method.
public class HelloMessage {
private String name;
public String getName() {
return name;
}
}

Example.......
● Upon receiving the message and extracting the name, the service will process it by creating a
greeting and publishing that greeting on a separate queue that the client is subscribed to. The
greeting will also be a JSON object, which might look something like this
{ "content": "Hello, Fred!"}
● To model the greeting representation, you add another plain old Java object with a content
property and corresponding getContent() method.
public class Greeting {
private String content;
public Greeting(String content) {
this.content = content;
}
public String getContent() {
return content;
}
}

Example.......
● GreetingController is mapped to handle messages to destination "/hello". STOMP messages can
be routed to controller.
● The @MessageMapping annotation ensures that if a message is sent to destination "/hello", then
the greeting() method is called.
● After the 3 second delay, the greeting() method creates a Greeting object and returns it. The return
value is broadcast to all subscribers to "/topic/greetings" as specified in the @SendTo annotation.
@Controller
public class GreetingController {
@MessageMapping("/hello")
@SendTo("/topic/greetings")
public Greeting greeting(HelloMessage message) throws Exception {
Thread.sleep(3000); // simulated delay
return new Greeting("Hello, " + message.getName() + "!");
}
}

Example.......
●
@Configuration indicate that it is a Spring configuration class.@EnableWebSocketMessageBroker enables WebSocket message
handling, backed by a message broker.
●
enableSimpleBroker() to enable a simple memory-based message broker to carry the greeting messages back to the client on
destinations prefixed with "/topic". It also designates the "/app" prefix for messages that are bound for @MessageMapping-
annotated methods.
● The registerStompEndpoints() method registers the "/hello" endpoint, enabling SockJS fallback options so that alternative
messaging options may be used if WebSocket is not available. This endpoint, when prefixed with "/app", is the endpoint that the
GreetingController.greeting() method is mapped to handle.
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {
@Override
public void configureMessageBroker(MessageBrokerRegistry config) {
config.enableSimpleBroker("/topic");
config.setApplicationDestinationPrefixes("/app");
}
@Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry.addEndpoint("/hello").withSockJS();
}
}

Web-Socket support
l
Hands on!!!!

Messaging Module
– By contrast a WebSocket application may use a single URL only for
the initial HTTP handshake. All messages thereafter share and flow
on the same TCP connection. This points to an entirely different,
asynchronous, event-driven, messaging architecture. One that is
much closer to traditional messaging applications (e.g. JMS,
AMQP).
– We uses Messaging with JMS(Java Message Service) to create,
send and read messages.
– This example walks you through the process of publishing and
subscribing to messages using a JMS broker.
– We’ll build an application that uses Spring’s JmsTemplate to post a
single message and subscribes to it with a @JmsListener annotated
method of a managed bean.

JMS Introduction
There are two types of messaging domains in JMS.
● Point-to-Point Messaging Domain.
– In PTP model, one message is delivered to one receiver only. Here, Queue is used as
a message oriented middleware (MOM).
– In PTP model, there is no timing dependency between sender and receiver.
● Publisher/Subscriber Messaging Domain.
– In Pub/Sub model, one message is delivered to all the subscribers. It is like
broadcasting. Here, Topic is used as a message oriented middleware that is
responsible to hold and deliver messages.
– In PTP model, there is timing dependency between publisher and subscribe.

Point-to-Point Messaging Domain

Example.......
●
The JmsListener annotation defines the name of the Destination that this method should listen to
and the reference to the JmsListenerContainerFactory to use to create the underlying message
listener container.
@Component
public class Receiver {
@Autowired
ConfigurableApplicationContext context;
@JmsListener(destination = "mailbox-destination", containerFactory =
"myJmsContainerFactory")
public void receiveMessage(String message) {
System.out.println("Received <" + message + ">");
context.close();
FileSystemUtils.deleteRecursively(new File("activemq-data"));
}
}

Example.......
@SpringBootApplication is a convenience annotation that adds all of the following:
●
@Configuration tags the class as a source of bean definitions for the application context.
● @EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and
various property settings.
● @ComponentScan tells Spring to look for other components, configurations, and services in the the hello package,
allowing it to find the Receiver.
@EnableJms triggers the discovery of methods annotated with @JmsListener, creating the message listener container
under the covers.
For clarity, we have also defined a myJmsContainerFactory bean that is referenced in the JmsListener annotation of the
receiver. This creates a SimpleMessageListenerContainer, an asynchronous message receiver that is fired up when the
application context starts.
Spring provides a convenient template class called JmsTemplate. JmsTemplate makes it very simple to send messages to
a JMS message queue. In the main runner method, after starting things up, you create a MessageCreator and use it from
jmsTemplate to send a message.
Two beans that you don’t see defined are JmsTemplate and ActiveMQConnectionFactory. These are created automatically
by Spring Boot. In this case, the ActiveMQ broker runs embedded.
By default, Spring Boot creates a JmsTemplate configured to transmit to queues by having pubSubDomain set to false. The
SimpleMessageListenerContainer is also configured the same. To override, set spring.jms.isPubSubDomain=true via
Boot’s property settings (either inside application.properties or by environment variable). Then make sure the receiving
container has the same setting.

Example.......
●
The JmsListener annotation defines the name of the Destination that this method should listen to and the reference to the
JmsListenerContainerFactory to use to create the underlying message listener container.
@Bean
JmsListenerContainerFactory<?> myJmsContainerFactory(ConnectionFactory connectionFactory) {
SimpleJmsListenerContainerFactory factory = new SimpleJmsListenerContainerFactory();
factory.setConnectionFactory(connectionFactory);
return factory;
}
public void sendMessage(ConfigurableApplicationContext context){
// Clean out any ActiveMQ data from a previous run
FileSystemUtils.deleteRecursively(new File("activemq-data"));
// Send a message
MessageCreator messageCreator = new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
return session.createTextMessage("ping!");
} };
JmsTemplate jmsTemplate = context.getBean(JmsTemplate.class);
System.out.println("Sending a new message.");
jmsTemplate.send("mailbox-destination", messageCreator);
}

Messaging support
l
Hands on!!!!
http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html

Unit Testing
Integration Testing
Testing

Spring in Junit testing
Why Spring in testing?
●
Many things reamins untested e.g. request mapping,
data binding, type conversions and validation.
●
Controller methods such as @InitBinder,
@ModelAttribute, and @ExceptionHandler also get
called as part of processing the request.

●
In Spring 3.0, @Configuration was introduced for
Java based configuration. However the
TestContext framework did not provide support
fro this.
●
In 3.1 AnnotationConfigContextLoader was used
and @ContextConfiguration annotation is
updated to support @Configuration.

Creating a Unit Test Class
To load ApplicationContext two annotations are used:
●
@RunWith(SpringJUnit4ClassRunner.class)
●
@ContextConfiguration(locations = {...}): Indicates which XML
files contain the ApplicationContext.

How it works?
Spring 3.0:
@ContextConfiguration
public class OrderServiceTest {
@Autowired
private OrderService orderService;
}

How it works?
Spring 3.1 (Java Configuration Support):
@ContextConfiguration(loader=AnnotationConfigContextLoad
er.class)
@Configuration
static class ContextConfiguration {
@Bean
public OrderService orderService() {
OrderService orderService = new OrderServiceImpl();

How it works?
Spring 3.1:
// set properties, etc.
return orderService;
}
}
@Autowired
}

How it works?
Spring 3.1 (When we want to use bean defination from
other java class):
@Configuration
public class OrderServiceConfig {
@Bean
public OrderService orderService() {
OrderService orderService = new OrderServiceImpl();
// set properties, etc.
return orderService;
}

How it works?
Spring 3.1 (When we want to use bean defination from
other java class):
@ContextConfiguration(classes=OrderServiceConfig.class,
loader=AnnotationConfigContextLoader.class)
@Autowired
}

Spring in Integration testing
Why use Spring for Integration testing?
Spring IoC container caching.
Dependency Injection of test fixture instances.
Transaction management.
Spring-specific base classes.

Spring 4 testing
improvements
Groovy scripts can now be used to locad context for
integration testing.
How?
@ContextConfiguration({"/AppConfig.groovy",
"/TestConfig.Groovy"})
Context loading with annotated classes.
How?
@ContextConfiguration(classes =
{AppConfig.class, TestConfig.class})
public class MyTest {

Spring 4 testing
improvements
Annotated class can be one of the following:
@Configuration
A component @Component, @Service, @Repository
@Bean
If no class is defined then as per the default behaviour
search the static class in the test taht meets the
requirement of configuration.
●
@Configuration
●
static class Config {
// this bean will be injected into the
OrderServiceTest class
@Bean

Spring 4 testing
improvements
Test-managed transactions can be triggered and rolled
back per testcase bases.
TestTrduced with static methods like start(), end() and
isActive().
TransactionalTestExecutionListener supports the
@BeforeTransaction and @AfterTransaction
annotations to execute certain code before or after a
transactional test.
@Before and @After are executed as part of
transaction in each testcase but @BeforeTransaction
and @AfterTransaction are excluded from the
transactional scope.

Spring 4 testing
improvements
SQL scripts execution with @sql before or after the
integration test case. This annotation can be used at
class as well as method level.
How to declare?
@Test
@Sql({"/test-schema.sql", "/test-user-data.sql"})
public void userTest {
// execute code that uses the test schema and
test data
}

Spring 4 testing
improvements
SQL scripts execution can be restricted at transactional
level or at the execution phase level.
How to declare?
@Sql(
scripts = "delete-test-data.sql",
config = @SqlConfig(transactionMode =
ISOLATED),
executionPhase = AFTER_TEST_METHOD
)
public void userTest {
}

Spring 4 testing
improvements
Test property sources override application property
sources using the annotation @TestPropertySource.
How to declare?
Option 1:
@TestPropertySource("/test.properties")
public class MyIntegrationTests {
// class body...
}

Spring 4 testing
improvements
Test property sources can have inligned properties in the
form of key value pair using the properties attribute.
How to declare?
Option 2:
@TestPropertySource(properties = {"timezone =
GMT", "port: 4242"})
public class MyIntegrationTests {
// class body...
}

Testing Improvement
l
Hands on!!!!

Spring 4 advanced final_xtr_presentation

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