Introduction to Spring Boot.pdf

Why Spring Boot?
✦It’s popular & modern
✦It’s easy to use - practically like building a
command line app
✦Trivial to install
✦Provides integration to web services & Database
✦It’s still Java
✦It has integration to all major IDE’s

IDE Support
✦NetBeans - http://plugins.netbeans.org/plugin/
67888/nb-springboot
✦IntelliJ - https://www.jetbrains.com/help/idea/
2016.3/creating-spring-boot-projects.html
✦Eclipse - https://spring.io/tools/sts/all

So what is it?
Spring Boot makes it easy to create stand-alone,
production-grade Spring based Applications that
you can "just run". We take an opinionated view of
the Spring platform and third-party libraries so you
can get started with minimum fuss. Most Spring
Boot applications need very little Spring
configuration.
“

So what is it?
✦A set of tools that generate a single jar web app
✦Tomcat is bundled right in your fat jar
✦Literally just write a simple single class code
✦Deploy one jar to your server

MySQL
✦We will go with MySQL for storage
✦It’s easy to map it to JPA objects in Spring Boot
✦I chose it mostly for convenience as it had better
installers than MariaDB for Mac
✦You can use MariaDB as it should be compatible
✦MySQL is familiar, simple, performant & powerful

Why not NoSQL?
✦NoSQL is easier and more scalable on some
fronts but harder on others
✦Data migration to/from NoSQL is really diﬃcult
✦Reporting and query 3rd party tools aren’t as easy
✦Moving to NoSQL is easier than moving out of
NoSQL architecture
✦E.g. when Google needed performance for
search they used NoSQL when they needed
reliability for adsense they used SQL

Mini
Mission
© Codename One 2017 all rights reserved

Setup MySQL
✦Setup and configure MySQL create a database
✦Once installed launch the database daemon
process
✦Login to MySQL using a command similar to this:
/usr/local/mysql/bin/mysql -h localhost -u root -p

Configure Database
✦We’ll do the initial work in the test database
✦To create it we will need to issue:
CREATE DATABASE test;
✦Notice the db might require you to set your
password the first time around
UPDATE mysql.user SET
Password=PASSWORD('your_new_password') WHERE User='root';

Spring Boot

Spring Boot
✦Once the IDE plugin is installed getting started
with Spring Boot is really easy
✦In netbeans it looks roughly like this…

New Project
Initializr Project
Notice the specific project
type selection. This will allow
us to pick features for
inclusion later

New Project
Names
Most of these don’t matter
much for the test app except
for the package name & app
name which you will need to
use afterwards

New Project
Selections
Make sure to pick the
following: Web, Websocket,
Jersey, JPA & MySQL.
There are many other
interesting options but I want
to keep things simple

New Project
Important
After creation you might need
to resolve project issues so
maven can fetch
dependencies

Configure Database
✦Open application.properties
✦Configure mysql:
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=root
spring.datasource.password=*****
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update
spring.jpa.generate-ddl=true
spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect

The Main App
✦The main app of bootstrap doesn’t do much:
package com.codename1.testapp;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class TestAppApplication {
public static void main(String[] args) {
SpringApplication.run(TestAppApplication.class, args);
}
}

Something
Useful

JPA Storage
✦Lets store some elements into MySQL
✦We’ll use JPA (Hibernate)
✦JPA allows us to map objects to database tables
and mostly hides SQL
✦I won’t go into the working/philosophy behind it
and use it in a relatively simplistic way

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Item {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String name;
private boolean marked;
private boolean deleted;
private String owner;
public Item() {}
public Item(Long id, String name, boolean marked, boolean deleted, String owner) {
…
}
}
Item

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Item {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String name;
private boolean marked;
private boolean deleted;
private String owner;
public Item() {}
public Item(Long id, String name, boolean marked, boolean deleted, String owner) {
…
}
}
Item
Trimmed Code
I trimmed a lot of boilerplate
code, the method body,
getters/setters to all the
elements

import java.util.List;
import org.springframework.data.repository.CrudRepository;
public interface ItemRepository extends CrudRepository<Item, Long> {
List<Item> findByOwner(String owner);
}
ItemRepository

import java.util.List;
import org.springframework.data.repository.CrudRepository;
public interface ItemRepository extends CrudRepository<Item, Long> {
List<Item> findByOwner(String owner);
}
ItemRepository
CRUD
Spring injects the
implementation of this interface.
It includes API’s for Create,
Read, Update & Delete for the
entity.

@Controller
@RequestMapping("/item")
public class ItemService {
@Autowired
private ItemRepository repo;
@RequestMapping(method=RequestMethod.GET)
public @ResponseBody Item[] go(@RequestParam(value="id", required=false) Long id,
@RequestParam(value="owner", required=false) String owner) {
if(id != null) {
Item c = repo.findOne(id);
return new Item[] {c};
}
if(owner != null) {
List<Item> c = repo.findByOwner(owner);
Item[] i = new Item[c.size()];
return c.toArray(i);
}
return new Item[0];
}
@RequestMapping(method=RequestMethod.PUT)
public @ResponseBody Item add(@RequestBody(required=true) Item i) {
i = repo.save(i);
return i;
}
}
ItemService

@Controller
@Autowired
if(id != null) {
}
if(owner != null) {
}
return new Item[0];
}
i = repo.save(i);
return i;
}
}
ItemService
Injection
This value is injected implicitly
by Spring

@Controller
@Autowired
if(id != null) {
}
if(owner != null) {
}
return new Item[0];
}
i = repo.save(i);
return i;
}
}
ItemService
Bad Design
I’m returning the Item object
which is an Entity & an internal
representation of the database.
This is bad design as I might
expose internal state!  
I’m doing it here as a shortcut

Add an Item
✦We can add an item using this curl request:
curl -H "Content-Type: application/json" -X PUT
-d '{"name":"Item Name", "marked":false, "deleted":false, "owner":"Shai"}'
http://localhost:8080/item
✦The output is:
{"id":1,"name":"Item Name","marked":false,"deleted":false,"owner":"Shai"}

Fetch My Items
✦We can fetch my items using:
curl http://localhost:8080/item?owner=Shai
✦The output is:
[{"id":1,"name":"Item Name","marked":false,"deleted":false,"owner":"Shai"},
{"id":2,"name":"Item Name","marked":false,"deleted":false,"owner":"Shai"},
{"id":3,"name":"Item Name","marked":false,"deleted":false,"owner":"Shai"}]

What did we learn?
✦Why we chose Spring Boot and why it’s cool
✦How to set it up with MySQL
✦Implementing a restful service that’s moderately
useful with almost no code…

Introduction to Spring Boot.pdf

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