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Java REST Web Services, Microservices and fullstack

developmentRony Keren

Internet Team

John-Bryce

1

Topics

• Architecture• Tier model

• RPC

• SPA

• REST based Web Services

• Microservices

• Full-stack Development• AngularJS

• Spring Boot

2

Architecture

3

Architecture

• Classic MVC

Designed to separate client flow and interaction from business model that serves the client request and from the final output.

• Traditional MVC as used in web modules – MVC Model 2

MVC Model 2

Model•Represents underlying data and business logic

View•User interface / UI generator•Presents model data

Controller•Connects the model and the view and used to communicate between them

notify

4

Architecture

• In JEE :

Controller – Servlet (automated in JSF)

View – JSP

Model – EJB

J2EE Presentation Tier patterns

• Service To Work – MVC Model 2

• Dispatcher View– MVC Model 1

MVC Model 2

5

Architecture

• Service To Work - MVC Model 2

• Better since:• View and model communicated through value objects

• Trivial server side code is embedded in views

• But, views are still a mix of server & client code...

controllershow data model

view 1

view 2

view 3

get data

dispatch

client

6

Architecture

• Dispatcher View model

• Here, views are used also for ‘controlling’.

• Tightly coupling between views and model

• Can be considered for very simple modules


view 1

view 2

view 3

set data

dispatch

client

get data

7

Architecture

• Mixing server side code in view causes some serious problems:

Value objects embedded in HTML

It is never just HTML…(CSS, Jscript…)

What if client requires something else than HTML ??

The problem with views

8

Architecture

• List of web frameworks that should help:

• So many… means that:

none is really good enough…

maybe problems can’t be solved with MVC model 2


Echo, Cocoon, Millstone, OXF, Struts, SOFIA, Tapestry, WebWork, RIFE, Spring MVC,

Canyamo, Maverick, Jpublish, JATO, Folium, Jucas, Verge, Niggle, Bishop, Barracuda, Action

Framework, Shocks, TeaServlet, wingS, Expresso, Bento, jStatemachine, jZonic, OpenEmcee,

Turbine, Scope, Warfare, JWAA, Jaffa, Jacquard, Macaw, Smile, MyFaces, Chiba, Jbanana,

Jeenius, Jwarp, Genie, Melati, Dovetail, Cameleon, Jformular, Xoplon, Japple, Helma,

Dinamica, WebOnSwing, Nacho, Cassandra, Baritus, Stripes, Click, GWT, Apache Wicket

9

Architecture

• AJAX – bigger than it seems…

• AJAX technology encourages web modules to ‘talk’ using XML / JSON rather than HTML


10

Architecture

• View of classic architecture

Introduction to AJAX

HTML 2

HTML 1

CGI Engine

Web ServerBrowser

HTTP Request

HTTP Response

11

Architecture

• View of AJAX architecture

Introduction to AJAX

HTML

CGI Engine

Web ServerBrowser

HTTP Request

HTTP Response

12

Architecture

• Using AJAX, web modules can focus on transferring data rather than view

Client receives a single HTML loaded with Jscript functions & callbacks

Jscript caller functions sends request data

Jscript callback processes response and renders it to page

Finally !• web modules input & output can be based on structured, self descriptive text formats

• Future non-HTML clients may use the same modules & data

Moving to single page applications

13

Architecture

• MVC Model 2

Views are generated on server side

• The ‘new’ MVC

Views are handled by the client

Communication between client and server is based on data

Moving to single page applications


view 1

view 2

view 3

get data

dispatch

client

SERVER

controllerrequest model

get dataClient

SERVER

view data

14

Architecture

• Why is it so important to ‘talk’ via XML/JSON and not ‘draw’ HTMLs ?

• Internet is much more than visiting web-sites…

• Future client of the internet are not going to use keyboards and screens… HTML might be irrelevant

Future internet clients

15

Architecture

• Phones & voice over IP networks

• Smart cards

• Chips

• Nanotechnology


16

Architecture

But the new ultimate client is US

• No hardware, no UI – just us

• Ability to share data directly from & to our brains


17

Architecture

• The ‘new’ MVC


controllermodel

get data

SERVER

view

request

data

18

Architecture

What is JSON ?

• Java Script Object Notation

• Also self-descriptive text based protocol

• Used for marshalling and un-marshalling Jscript objects

XML vs. JSON

{

“people”: [

{ “name": “David“, “age": “20“},

{ “name": “Dana“, “age": “25“},

{ “name": “Eve“, age": “30“},

]

}

19

Architecture

Why is it an alternative for XML ?

• Better for small applications (like client side apps)

No parsers are needed

Contracts are less critical

Light integration

• Jscript and Android developers prefers it

Got popular APIs for binding, handling & presenting JSON based data

XML vs. JSON

20

Architecture

JAXB supports JSON as well

• Root class is denoted with @XMLRootElement

• No schema is needed – all adjustments are done with JAXB annotations

JSON has no strong standards as XML (yet..)

XML vs. JSON

21

RPC

• Architecture & terms

• RPC in Java & JEE

• RPC Framework requirements

• XML for RPC – Web services

22

RPC

Remote Procedure Call

• Client invokes method on a Remote Object over a network

• Client obeys a contract which is the Remote Interface

• Remote object is a resource

• Remote method is a service

• In order to communicate both client & server uses sockets

Socket communication is determined according to the remote interface

Stub - Client side socket

Skeleton – server side socket that is used as a proxy to the remote object

Architecture & Terms

23

RPC

Architecture & Terms

skeleton

RemoteObject

get data

SERVERRemoteInterface

CLIENT

stub

public int sum (int x, int y);

public int sum (int x, int y){return x+y;

}

String action=in.readUTF();int x=in.readInt();int y=in.readInt();out.write(ro.invoke(action,x,y));

out.writeUTF(“sum”);out x=out.writeInt(5);out y=out.writeInt(6);int result=in.readInt();

User input is : 5, + , 6

Result is : 11

24

RPC

• RMI – Remote Method Invocation

provides a 2-tier infrastructure for Java clients

rmic – is a compiler that generates stubs & skels

• IDLJ

provides a 2-tier infrastructure for IIOP based clients

idlj – generates Java stubs & skels out of IDL files

• EJB – Enterprise Java Beans

provides a full 3-tier infrastructure

supports all protocols

RPC in JEE

25

RPC

• EJB – Remote Objects

Synchronous• Stateless Beans (pooled)

• Stateful Beans (passivated)

• Supports HTTP, Java IO, IIOP

A-synchronous• Message Driven Beans (JMS)

• Both P2P & Publisher-Subscriber methods are supported

RPC in JEE

26

RPC

• 2-tier vs. 3-tier RPC

• Stateless EJBs are pooled and served on-demand

RPC in JEE

skeleton

RemoteObject

get data

RMI Containerstub

skeletonstub

skeletonstub

skeletonstub

skeleton

EJB Container

stub

skeletonstub

skeletonstub

skeletonstub

Manager

RO Pool

RO

RORO

RO

27

RPC

• For server development

Map services to generate a contract

Expose the contract

Instantiate & publish the resource (or resource pool)

Create skeleton when requested

• For client development

Generate stub according to a given contract

RPC Framework Requirements

28

RPC

• Main goal of XML is for application integration

• If the contract is in XML format it can be:

describing services written in any language

used by any client

• If the stubs & skels will ‘talk’ via XML:

each may be written in a different language

xsd types can be used to describe primitives & objects

XML for RPC – Web Services

29

RPC

XML for RPC – Web Services

skeleton

RemoteObject

get data

SERVERXMLCLIENT

stubXML Request

XML Response

30

REST based Web Services

• Parallel computing

• NoSQL DBs

• Saving bandwidth & faster response

Introduction to REST

HTTP for RPC

JAX-RS - RESTful

• Creating a Java service

• Publishing & testing

• Using Jersey client API for generating clients

• Tokens & session management

• WADL

• JEE support

Big data – the challenge

31


• From single & concurrent to parallel & cloud computing

• Using NoSQL DB in addition to the classic relational DB

• Saving bandwidth & performance

XML is a very inefficient protocol uses tags to wrap data

XML forces the use of parsers

SOAP is an additional protocol on top of HTTP

Big data – the challenge

SOAP Message

SOAP Envelope

SOAP Attachments

SOAP Header

SOAP Body

SOAP Elements

HTTP Message

HTTP headers

HTTP body

32


REST – REpresentational State Transfer

• is an HTTP ‘enrichment’ that provides advanced RPC

passing data in any format including XML, JSON and binary data

REST can be counted as part of HTTP unlike SOAP which is a separate protocol

Introduction to REST

33


Client may use the following HTTP features in order to invoke a service:

• URI – path can determine the endpoint class and even method

• ACCEPT header – used by the client to specify response MIME type

service methods may result in different MIME types

client call can be delegated to method that produces the MIME type it expects

• METHOD – GET, POST, DELETE, PUT, HEAD

each method can be mapped to several HTTP-methods

client call is delegated to the method matches client HTTP request method

HTTP for RPC

34


• Suggested way to implement business according to HTTP method

HTTP for RPC

CollectionSingle elementHTTP Method

Fetch the whole collectionFetch an element from a collection

GET

Override one collection with a new one

Replace or create new element in a collection

PUT

Add new value to a collectionAssign a value to an objectPOST

Delete the entire collectionDelete a specific element from a collection

DELETE

35


• Java API for creating RESTful based web-services

Uses Jersey implementation as RI

• Uses annotations much like JAX-WS

• 4 principles to make it fast and simple:

Identify – tracking endpoints is based on URI

Unified interface – using HTTP methods (GET,POST,DELETE,PUT…)

Self descriptive content – XML , JSON…

Stateful interaction – by attaching session data or using tokens

• JAXB used for XML and JSON

JAX – RS - RESTful

36


• Acts as a REST server

Provides a servlet to proxy REST activity

Provides basic client capabilities for testing

Default scope for services is ‘request’

Jersey Client API is not part of the standard

Java RI is called Jersey

37


• @Path

Class & method level

Sets the URI pattern that points to the underlying resource

May take path parameters to use later

When used in both class & method:

JAX – RS Annotations

@Path("/helloworld/{userName}")

@Path("/helloworld") public class HelloWorldService { …

@Path("/helloworld") public class HelloWorldService {

@Path("/doIt") public void doSomething(){…

38


• @GET/ @POST/ @PUT/ @DELETE

Method level or class level (for all methods)

Define the HTTP request type that the method replies to


@Path("/helloworld") public class HelloWorldService {

@POSTpublic void doSomething(){…

39


• @PathParam

Method level

Maps a @Path parameter to a method parameter


@Path("/helloworld/{userName}")public class HelloWorldService {

@GETpublic String getUser(@PathParam("userName") String user){ …

40


• @Produces / @Consumes

Method level

Specifies the MIME type the operation produces / consumes

• @QueryParam & @DefaultValue

Parameter level

Specifies HTTP request value & default values


@GET@Produces(“text/plain") public String getTextData(){ …

@DefaultValue("2") @QueryParam(“num") int num;…

41


• Step 1 - Create web project with some business logic

Building and publishing RESTful module:

package hello.in.different.formats;@Path("/hello")public class Hello {

@GET@Produces(MediaType.TEXT_PLAIN)public String sayTextHello() { return "Hello JAX-RS !"; }

@GET@Produces(MediaType.TEXT_XML)public String sayXMLHello() {

return "<?xml version=\"1.0\"?>" + "<hello> Hello JAX-RS" + "</hello>"; }

@GET@Produces(MediaType.TEXT_HTML)public String sayHtmlHello() {

return "<html> " + "<title>" + "Hello JAX-RS" + "</title>" + "<body><h1>" + "Hello JAX-RS " + "</body></h1>" + "</html> "; }

}

This format can be shown in browsers

42


• Step 2 – Configure Jersey servlet and register “hello” WS


<?xml version="1.0" encoding="UTF-8"?> WEB-INF\web.xml<web-app …>

<display-name>Hello In Different Formats</display-name> <servlet>

<servlet-name>Jersey REST Service</servlet-name> <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class> <init-param>

<param-name>com.sun.jersey.config.property.packages</param-name> <param-value>hello.in.different.formats</param-value>

</init-param> </servlet><servlet-mapping>

<servlet-name>Jersey REST Service</servlet-name><url-pattern>/rest/*</url-pattern>

</servlet-mapping> </web-app>

43


• Client may choose format byspecifyingmedia-type:

Combining with JAXBpackage hello.in.different.formats.jaxb;@Path("/phoneBook")public class Hello {

@GET@Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})public Entry getEntry(String client name) {

Entry e = new Entry(); //load data into entry by the given namereturn e;

}

}

These format involves application format pre-processing - JAXB

package hello.in.different.formats.jaxb;

@XMLRootElementpublic class Entry{

private String name;private String phone;private String cellPhone;

//public getters and setters…}

System.out.println(service.path("rest").path(“phoneBook").accept(MediaType.APPLICATION_JSON).get(String.class));

JAXB annotationto enable

marshalling & un-marshalling Entry

44


• When assigning structured data (XML/JSON)

Make sure your class has default constructor

JAXB uses set() methods when un-marshaling

Clients may assign JSON/XML

Combining with JAXB

package hello.in.different.formats.jaxb;@Path("/phoneBook")public class Hello {

@GET@Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})public Entry editEntry(Entry toEdit) {

// edit entry…return e;

}

}

package hello.in.different.formats.jaxb;

@XMLRootElementpublic class Entry{

private String name;private String phone;private String cellPhone;

public Entry(){}…

}

45


• Step 3 – Deploy, run and test the service

Use this URL to invoke the service:

Note that the Jersey client is seeking for HTML formats


http://ip:port/root-context/rest/hello

Root Context, usually your project name

The URL pattern to call Jersey servlet

The name of the resource (service)

46


• Jersey offers simple client API

Creating RESTful client

public class Test { public static void main(String[] args) {

ClientConfig config = new DefaultClientConfig(); Client client = Client.create(config); URI baseUri = UriBuilder.fromUri("http://ip:port/hello.in.different.formats").build();WebResource service = client.resource(baseUri ); // Get plain textSystem.out.println(service.path("rest").path("hello").accept(MediaType.TEXT_PLAIN).get(String.class)); // Get XMLSystem.out.println(service.path("rest").path("hello").accept(MediaType.TEXT_XML).get(String.class)); // The HTMLSystem.out.println(service.path("rest").path("hello").accept(MediaType.TEXT_HTML).get(String.class));

}

get(..) / post(..) / put(..) / delete(..)

47


• It is very easy to use Servlets API in your services

• Why would we do it?

Scope management request, session, application

Do some custom request / response processing

• How do we use it?

Simply inject anything needed from Servlets API• Request, response, context…

• Use @Context

Working with CGI

@Path("/phoneBook") public class Hello {

@Context private HttpServletRequest req;@Context private ServletContext ctx;…

}

48


• On server side – simply inject HttpServletRequest

Use req.getSession(..) in order to• obtain HttpSession instance

• embed a session cookie

• Use session’s attributes to hold user session state

• On client side – you need to plant the session cookie on each request

To do that we obtain all response cookies

Then we place all cookies (including session cookie) on your request via builders

Builder is held in a WebResource object

Since WebResource are immutable – the only way to load cookies on it is via builder

Session management

49


• Server side

• Client side

Session management

@Path("/shop") public class StoreCart {

@Context private HttpServletRequest req;…public void startSession(){

HttpSession session = req.getSession(true); }

ClientResponse resp = service.path(“somePath").accept(…).get(ClientResponse.class);

WebResource wr=service.path(“someOtherPath");WebResource.Builder builder=wr.getRequestBuilder();for(Cookie c:resp.getCookies()){

builder.cookie(c);}…builder.accept(…);

• get response with session cookie• build a request (WebResource)• obtain Builder in order to update request• load all cookies from response onto builder• submit request via builder

50


• In web.xml:

1-Define roles

2- Set authentication method (also in web.xml)

Applying declarative security

<security-role><role-name>admin</role-name>

</security-role>

<login-config><auth-method>BASIC</auth-method>

</login-config >

51


• In web.xml:

3-Map roles to url patterns of your RESTful servlet


<security-constraint><web-resource-collection>

<url-pattern>/rest/*</url-pattern><http-method>POST</http-method>

</web-resource-collection><auth-constraint>

<role-name>admin</role-name></auth-constraint>

</security-constraint>

52


• 4- Use security annotations to declare roles access on your service


package hello.in.different.formats;@Path("/hello")@RolesAllowed({“admin”,”guest”})public class Hello {

@RolesAllowed(“admin”)@GET@Produces(MediaType.TEXT_XML)public String sayXMLHello() {

return "<?xml version=\"1.0\"?>" + "<hello> Hello JAX-RS" + "</hello>"; }

@PermitAll@GET@Produces(MediaType.TEXT_HTML)public String sayHtmlHello() {

return "<html> " + "<title>" + "Hello JAX-RS" + "</title>" + "<body><h1>" + "Hello JAX-RS " + "</body></h1>" + "</html> "; }

}

Security annotations: • @RolesAllowed – lists permitted roles• @DenyAll – allows non-logged users• @PermitAll – permits all declared roles• None – available to anyone

53


• Add ‘HTTP Basic Authentication’ header to the HTTP

• May use Jersey HttpBasicAuthFilter to do that

Adds the header only if doesn’t exist

Accepts username and password

Username and password are for creating user Principal

Principals are then mapped to application roles

Performing BASIC authentication

54


• Performing BASIC authentication – example: public class Test { public static void main(String[] args) {

ClientConfig config = new DefaultClientConfig(); Client client = Client.create(config); client.addFilter(new HTTPBasicAuthFilter("username", "password“ ));URI baseUri = UriBuilder.fromUri("http://ip:port/hello.in.different.formats").build();WebResource service = client.resource(baseUri ); …

}

55


• XML format

• Describes how to use a web resource

Path

Request method

Request parameters

Response format

• Target – REST client stub auto-generation

• Status

WADL was promoted by SUN to become a W3C standard - not yet

Java support for WADL • By open source tools (like AXIS for XML based WS)

• Wadl2java utility…

• Not included in JAX-RS & JEE6

Web Application Description Language - WADL

56


Main elements

• <application> - the root element

• <grammars> - includes *.xsd which may describe response content (if it

is XML based) – optional

• <resources> - contains all the resources described in the document

• <resource> - describe the resource itself, holds the path to it

<method> - describes a method for the invocation (GET/POST….)• <request> - describes the request and response structure

• <param> <option> - describe a parameter name, type (xsd:) and optional values

• <representation> - specifies request body MIME-TYPE

• <response> - describes the response status code and its MIME type

• <representation> - specifies response body MIME-TYPE

WADL

57


• WADL – simple example

<application xmlns="http://wadl.dev.java.net/2009/02"> <resources base="http://example.co.il/rest">

<resource path="employees"> <method name="GET"/> <method name="POST"/>

</resource></resources>

</application> Calling to http://example.co.il/rest/employeesis available via POST & GETPOST – probably add a new employeeGET – fetch employee list

58


WADL - placeholder for path-param


<resource path="employees"> <resource path="{empId}">

<param required="true" name="empID"/> <method name="GET"/>

</resource></resource>

</resources></application>

Calling to http://example.co.il/rest/employees/1234is available via GETempId will get the value 1234 and delegates it to the empID method parameter

59


WADL - placeholder for query-param


<resource path="employees"> <method name="GET">

<request> <param required="false" default="1" name="empID"/>

</request></method></resource>

</resources></application>

Calling to http://example.co.il/rest/employees?1234is available via GETempId will get the value 1234 and delegates it to the empID method parameter

60

Microservices

61

Introduction

• Microservices – Architectural style of composing application out of loosely coupled services.

• Services are mostly fine-grained

• Protocols are common and lightweight

• “Microservices is a variant of the service-oriented architecture (SOA) architectural style that structures an application as a collection of loosely

coupled services” (wiki)

62

• History

• Web-Services (XML based)

• EAI – Enterprise Application Integration

• Web-Services (REST based)

• SOA – Service Oriented Architecture (both XML & REST)

• Microservices (mainly REST)

Introduction

63

Introduction

• Monolithic Architecture pattern

• Classic pattern

• In use for most applications

• Structure: Single application with multiple modules & tiers All modules are part of the application

All modules are somehow depends on others

Deployed as one unit to a domain

Domain

DB

Server(s)

Application

web services logic DAO

64

Introduction

• Microservice Architecture pattern

• New approach

• Structure: Application is actually a flow between services

All modules are broken down to fine-grained standalone services

Services may interact with others and use different types of storages

Each service is separately : maintained, deployed, monitored

Domain

DB

Server(s)

service

Server(s)

service

Server(s)

service

Server(s)

serviceServer(s)

service

Server(s)

service

65

Hotel Domain

members

customers

roomAv.warRoomAvailabilityService

members.warMembershipService

payment.warPaymentService

Hotel System & Storage

Introduction

66

Introduction

• Each services may have:• its contract (interface)

• its own deployment settings

• Its own container / server instance(s)

For new developments - design for service

For existing application - decompose

67

Introduction

• Pros• Improved modularity • Easier to maintain • Easier to replace• Strong version control – rollbacks can be non-issue • Better unit testing • Parallel development • Continuous refactoring • Continuous deployment• Service may count on multiple alternative services for failover • Easily automated • Focused & independent administration

68

Introduction

• Cons• Intensive HTTP communication (still text based…)

• Going stateless? Not always… and then what?

• 2-phase commit is not supported in any Microservice – so can’t be used…

• Higher costs – each Microservice comes with its infrastructure….

• When Microservices span over different systems or divisions few challenges emerges: Team communication

Need in good documentation

Testing is hard when more than single service is involved

• Not exactly the rapid way to develop smart tiny engines or prototypes for Startups

69

Introduction

• Some additional points:

• Being standalone doesn’t mean you can’t use shared memory & resources

• HTTP is mostly used but other protocols can perform intra-service-

communication

• Independent deployment is very important for automation

70

Introduction

• Some additional points:

• Pack services according to roles:

Web integration (Front-end, REST WS)

Services – business facades & logic (billing, learning, reporting, notifications,

logistics…)

Repositories – DAOs, DBs & 3rd parties

• Different Microservices of the same ‘application’ can

• be written in different languages

• use different DB implementations

• run on different platforms and require a different deployment configuration

71

Introduction

• Scale cube & Microservices• Y – scale by running different parts of the application

• X – scale by running copies of the application

• Z – scale by splitting storage

• Microservices corresponds to the Y axis of the cube

Y axisfunction

decomposition

X axisfunction cloning

Z axisdata partitioning

72

Relevance

• Microservices are relevant for 3 trendy fields:

1. Fullstack development

2. BigData

3. DevOps

73

Relevance

• Fullstack development

• Fullstack developers have the following skills:

• Create some business logic

• Create API

• Provide SPA

• Deploy to a server

• Configure DB & other 3’rd parties

• Fullstack is very important as software development

• becomes more services-oriented

• requires intensive updates and new feature releases

74

Relevance

• BigData

• BigData forces:

• Parallel computing

• Dynamic domains (auto-scale)

• Effective resource management (especially for when using public clouds)

• In order to gain such capabilities it is better for application to

• use simple deployment schemes with minimal dependencies

• split pieces of software for optimal resource usage

75

Relevance

•DevOps

• Project development phases automation• One again…intensive releases & new features• Things must get automated, and when comes to

software in means: Test automation Version control Continuous deployment Continuous integration Automated monitoring and feedback system

• Automating all these aspects with monolithic architecture is mostly impossible

• When things a fine-grained they can be automated in most easy and sophisticated ways

76

Relevance

• DevOps – Microservices• Every Docker host is an active Image

• Kubernetes orchestrates Docker images

Ku

ber

net

es A

PI

DockerHost

DockerHost

Hardware

Hosting OS

Docker Engine

server

service

Hardware

Hosting OS

Docker Engine

server

service

DockerHost

Hardware

Hosting OS

Docker Engine

server

service

Kubernetes

ControllerHost

Network

77

Microservices Patterns

We may understand the meaning of implementing Microservices just scanning Microservices Patterns

78

Decomposing Patterns

• Relevant for existing monolithic systems

• Related patterns:

• 1 - Decompose by business capability

• 2 - Decompose by subdomains

79

Deployment Patterns

• How Microservices are deployed?

• Related patterns:

• 1 - Multiple service instances per host

• 2 - Service instance per host

• 3 - Service instance per VM

• 4 - Service instance per Container

• 5 - Server-less deployment

• 6- Service deployment platform

80

Application Infra Patterns

• Configuration is a major concern when decomposing into multiple services

• Assumes each service requires different configuration

• Related patterns

• 1 – Microservices Chassis (logs, health-checks, performance metrics.. )

• 2 – Externalized Configuration

81

Communication Patterns

• How does services communicate with each other?

• How does remote clients communicate with services?


• 1 – RPC

• 2 – Messaging

• 3 – Domain Specific Protocol

• 4 – Local Communication / Referencing

82

External API Patterns

• How should Microservices façade be implemented?


• 1 – API Gateway – single facade

• 2 – Backend for Frontend – multiple facades

83

Service Discovery Patterns


• 1 – Service Registry

• 2 – Client-Side Discovery

• 3 – Server-Side Discovery

• 4 – Self Registration

• 5 – 3rd Party Registration

84

Intra Invocation Patterns

• Related patterns• 1 – Circuit Breaker – track invocations, respond to failures

85

Data Related Patterns


• 1 – Database per Service

• 2 – Shared Database

• 3 – Saga Transactions

• 4 – Data Composition

• 5 – Command Query Separation

• 6 – Event Sourcing

86

Application Security Patterns


• 1 – Access Tokens

• 2 – Token-Role Map

87

Monitoring Patterns

• These patterns relates to logging, exception handling and monitoring aspects and they should be applied to Microservice based systems


• 1 – Log aggregation

• 2 – Application Metrics

• 3 – Audit Login

• 4 – Exception Tracking

• 5 – Health Check API

• 6 – Deployments & Changes Logging

88

Microservices Testing

• Microservice testing

• Like unit-tests Isolated

Simple

Cheep

Fast

• Will not provide application level QA

• Service Integration Contract testing

• Gateway test suites

• Each suite tests specific façade operation

• All involved underlying services must pass the test

89

Microservices Versioning

• Create new services every-time there is a significant change

• When meaningful upgrade is made or major logic fix is applied

Do not perform fix / upgrade on existing services

Create new one instead (!)

Keeping old versions allows you to

• Rollback back fixes & releases

• Provide multi-version support

• Each gateway proxies to its relevant versioned services

90

The Big Picture

91

SpringBoot

92

Topics

• Introduction to SpringBoot

• Relevance

• Maven projects - overview

• Downloading SpringBoot configuration with SpringMVC

• Configuring Eclipse Maven project

• Creating REST Microservice

• Running as stand-alone configuration with Tomcat instance

• Exporting as executable jar & launching

• Microservices communication with Spring restTemplate

93

Introduction to SpringBoot

• SpringBoot is a spring based repository which provides:

• Ready-to-use stand alone Spring application configurations

• Embedded Tomcat & Jetty as hosting containers

• Support for dependency customizations (WEB, JPA, JMS….)

• Configuration code or XMLs elimination

94

Introduction to SpringBoot

• SpringBoot uses @Conditional behind the scene • @Conditional allow different configuration to be applied

• The decision making is implemented in conditional factory classes

• @SpringBootApplication extends @EnableAutoConfiguration• @CompoonentScan is used to automatically scan @Beans

• Scan is done on current and sub directories

SpringSpringBoot

user

95

Relevance

• DevOps & Automation

• Project become more & more agile

• Development moves into service-oriented integration

• Automated configurations and instances is easy when services are stand-alone units

• Microservices are fine-grained services with embedded web servers

• SpringBoot

• provides rapid mechanism to create stand-alone configurations

• great solution for Java based Microservice – just add WEB dependency

96

Relevance

• Full-stack Java Development

• Full-stack developer must be able to create and configure web services and Microservices

• Full-stack developers must have easy configuration and administration tools in order to focus on business logic, but mostly- ClientMVC

• SpringBoot

• Encapsulated complex configurations

• Supports rapid development with SpringMVC and other extensions

97

Projects

• Maven build automation tool• Uses pon.xml to define package and dependencies

• Code is downloaded from Maven Central Repository

• The code is stored in C:\Users\{your_user_name}\.m2

• Maven with IDEs• Maven projects are bounded to the .m2 directory

• Projects can be updated at any time, usually after editing pom.xml

• Project can be exported with all Maven dependencies as stand-alone jar

98

Maven Projects

• SpringBoot configuration pom.xml example: <?xml version="1.0" encoding="UTF-8"?>…

<groupId>com.example</groupId><artifactId>boot</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging>

<name>boot</name><description>Demo project for Spring Boot</description>

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.4.RELEASE</version><relativePath/> </parent>…

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>…

99

Maven Projects

• Eclipse Maven Projects

• Base Structure• src\package.name – where you add packages and classes

• src directory – where java source copies are automatically stored

• target directory – where classes automatically generated from source copies

• pom.xml

• When editing pom.xml• right click your project and choose Maven->Update Project

• Notice that Eclipse is downloading libraries and update builds

100

Maven Projects

• Eclipse Maven Projects

• Exporting Maven projects as stand-alone jars• right click your project and choose ->Run As>Maven Install

• jar file is default location is: workspace\{your_project}\target

• If exported as executable jar – use java –jar {your_jar_name}.jar to launch

101

Maven Projects

• Maven build automation tool• Uses pom.xml to define package and dependencies

• Code is downloaded from Maven Central Repository

• The code is stored in C:\Users\{your_user_name}\.m2

• Maven with IDEs• Maven projects are bounded to the .m2 directory

• Projects can be updated at any time, usually after editing pom.xml

• Project can be exported with all Maven dependencies as stand-alone jar

102

Downloading SpringBoot configuration

• Visit: https://start.spring.io

• Spring Initialzr builds SpringBoot configurations with• Maven / Gradle• Java / Kotlin / Groovy• Various SpringBoot versions

• Default is Maven / Java / SpringBoot 1.5.*

• Dependencies can be added

• The only requirement for stand-alone Microservice is WEB dependency• Adds SpringMVC & Embedded default web server (Tomcat)

• Press ‘Generate Project’ to download a complete Maven project plus basic code example & test packed in ZIP format

103


104


• Basically, any spring extension can be added later by editing pom.xml but,

• Here’s a list of keywords to search for getting a ready to use pom.xml

• Main dependencies• DB

• JDBC • MySQL• PostrgeSQL• SQL Server• AWS JDBC• JPA

• NoSQL & In memory• REDIS• MongoDB & Embedded MongoDB• Cassandra

105


• More dependencies

• Web• SpringMVC• Jersey JAX-RS• Web Services JAX-WS• Vaadin (Java web framework)• ApacheCXF• WebSocket

• Others• Security – Spring Security• Elasticsearch• Mobile – Spring Mobile for Mobile web apps• Messaging

• KAFKA• JMS – Active MQ

• Spring Cloud

106

Configuring Eclipse Maven project

• Importing Maven project to Eclipse workspace• Simplest way is to generate a new Maven Project

• When generating new project make sure the following fields:

• groupID

• artifactId

• Version

has the same values as in pom.xml (located at your downloaded project ZIP file)

• Now, simply override your eclipse project pom.xml with the project ZIP pom.xml

• Update project from Maven menu in order to download all dependencies

• You may import the examples included in the ZIP file as well by placing it under:

your project -> src/main/java & src/test/java

107

Configuring Eclipse Maven project

• Changing to Jetty• Edit pom.xml

• Update project

…<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> …

108

Creating REST Microservice

• Create new class under srv/main/java• Make sure to use package(s) declaration

• You may edit sample controller which was auto generated

• Spring Boot • @SpringBootApplication

• General class level annotations• @Controller

• @EnableAutoConfiguration

• When using Dependency Injections make sure to:• Put @ComponentScan on class level

• Make sure all DI classes are at the same or sub packages

109


• Main Spring & Spring MVC annotations• @Autowired

• @Component

• @Scope("singleton") / “request” / “session”

• Main SpringMVC REST annotations• @RequestMapping value="" method=""

• @PathVariable

• @QueryParam

• @ResponseBody

110


• Main method• In order for the service to be executable – a main method is implemented

• Main() will launch all configurations including Tomcat

…@Controller@SpringBootApplicationpublic class SampleController{…

public static void main(String[] args) throws Exception {SpringApplication.run(SampleController.class, args);

{{

111


• Adding clients

• After launching service, there 2 common client options:• Java REST API used to test or invoke other Microservices

• Client API – static pages based on HTML & JavaScript

• Later we’ll discuss using Spring restTemplate as Java REST client API

112


• Adding static content• Using static web content (SPA, Client MVC frameworks)

• SpringBoot automatically scans and deploy static web content from:• /META-INF/resources/

• /resources/

• /static/

• /public/

• None is included in the plain web template - so create one• Place all HTMLs, CSSs & JS in directories inside

Calling: http://localhost:8080/hello.html

113

Running as stand-alone with Tomcat instance

• Launching from Eclipse is easy• Simply run your controller as a Java Application

• Controller is automatically deployed and available by default at:

http://localhost:8080/

114

Running as stand-alone with Tomcat instance

• Change default port• Port can be set with system properties

• Spring loads system properties from src/main/resources/application.properties file

• Since default configuration comes with no configuration files – you need to create it

src/main/resource/application.properties

server.port = 8090

115

Exporting as executable jar & launching

• SpringBoot comes with a Maven plugin

• Maven is capable if downloading and including dependencies when exporting projects – repackaging

• In order to generate a stand-alone jar with all Maven dependencies:• Right click your project and choose ->Run As ->Maven Install

• jar file is default location is: workspace\{your_project}\target

• To launch jar use the following command:

java –jar { jar_name }.jar

116

Microservices communication with RestTemplate

• We can use SpringBoot to create, export and launch Microservices

• Since Microservices are stand-alone units• In many cases one Microservice invokes another

• We need REST client API in our SpringBoot configuration

• Configuring Spring restTemplate client • Add this to pom.xml

• Update project

…<dependency>

<groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope>

</dependency>

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId>

</dependency></dependencies>…

117


• Example: Getting Quote from StockMicroservice

• StockMicroservice getQuote() :

• Quote Bean:

…@RequestMapping("/quote/{symbol}")@ResponseBodypublic Quote getQuote( @PathVariable(“symbol”) String symbol

){Quote q=new Quote();q.setSymbol(symbol);q.setValue(db.loadCurrValue(symbol));return q;

}…

@JsonIgnoreProperties(ignoreUnknown = true) public class Quote{

private String symbol;private double value;

getXXX()/setXXX() {

Calling: http://localhost:8080/quote/ABC

Output example: {“symbol":“ABC",“value":333.33}

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• Example: Getting Quote from StockMicroservice

• Another Microservice that uses restTemplate to get Quote:

…public void callStockMicroservice(){

RestTemplate restTemplate = new RestTemplate();Quote quote = restTemplate.getForObject("http://localhost:8080/quote/ABC",

Quote.class);System.out.println(quote.getSymbol()+”-”+quote.getValue());

{

…

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