Stack

Simple REST backend service.

• Spring Boot
• Unit Test 4/5
• Mockito
• HSQL -> MYSQL

Task

• Client can apply for loan asking for amount and term
• Loan application evaluation: Application is risky if:
  • Loan application is done for max amount and loan application is created between 0:00–6:00
  • Client Applied 3 times using the same IP address
• Loan is granted if loan application goes through risk evaluation without errors.
• Once within loan term client can apply for term to be prolonged up to 14 days.

Planned

1. Add Swagger to recognize this service  https://swagger.io/resources/articles/best-practices-in-api-design/
2. Add docker and deploy service to AWS from GitHub
3. Add stemming libs from IoT .

Analyse

I assume that the risky loan request will be rejected.

Loan entity

static MAX_LOAN = 1000 – overrun

• loanId Int artifical id.
• Amount Long
• LoanName String
• Ip String
• TermAt Date
• historyLog String – info about allowed operations.
• CreatedAt Date
• UpdatedAT Date

example:

riskEvaluation

• amount > MAX_LOAN.
• createdAt <0:00 – 6:00>.
• ip same for 3 last apply in the same loanName.

UnitTest

• Take Loan < MAX_LOAN out of <00:00 – 06:00> – accepted.
• Take loan > MAX_LOAN – declined.
• Take loan from different IP.
• Take loan in different time <00:00 – 06:00>.
• TrolongTerm – check changes.
• Prolong two times loan – declined.

Impementation

• spring-boot-rest
• sample init data HSQL in import.sql
• junit test

Setting environment (InteliJ)

• http://start.spring.io/ – pom.xml
• -add-opens and dependency for jaxb-api for suppres warning Illegal reflective access by org.springframework.cglib.core.ReflectUtils$1 StackOverflow
• GROOVY_TURN_OFF_JAVA_WARNINGS=true temp fix WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1
• sample init data HSQL in import.sql.

REST APIs & logic

The app defines following simple CRU APIs. Without delete.

MAX_LOAN = 1000 define loan overrun defined in entity model as column.

@Column 
@NotNull(message = "Please enter correct amount of loan") 
@Min(0) 
@Max(MAX_LOAN) private long Amount;

Important case for variable entity ie nameLoan, cratedAt.

• GET http://localhost:8080 – show this rendered README.md about API.
• GET http://localhost/api/loans – get all lonas list (sample init data in import.sql)
• POST http://localhost/api/loans – create new loan example JSON:

Resposne

• GET http://localhost/api/loans/ – get id's loan. Example http://localhost:8080/api/loans/1

• PUT http://localhost/api/loans/ – not supported
• PUT http://localhost/api/loans/prolong/ – prolong loan 14d
• DELETE http://localhost/api/loans/

You can test them using postman (or any other rest client). Postman test collection: https://www.getpostman.com/collections/f4f319431e96e245d5a8

HSQL at mem

spring.datasource.url: jdbc:hsqldb:mem:restdb

Database Initialization

In a JPA-based applications, we can either choose to let Hibernate create the schema using entity classes or use schema.sql, but we cannot do both. Make sure to disable spring.jpa.hibernate.ddl-auto if using schema.sql in application.properties

application.properties

spring.jpa.hibernate.ddl-auto=on

Sample init data HSQL in import.sql.

drop table if exists loans CASCADE create table loans ( Id bigint generated by default as identity (start with 1), Amount varbinary(255) not null, CreatedAt timestamp not null, Ip varchar(255), LoanName varchar(20), ProlongedTerm boolean, TermAt timestamp, UpdatedAt timestamp, primary key (Id) )

Code Github

[simple_icon name="github"] https://github.com/karol-preiskorn/LoanREST

Help for Spring Boot REST

This module contains articles about Spring Boot RESTful APIs.

Relevant Articles

• HATEOAS for a Spring REST Service
• Versioning a REST API
• ETags for REST with Spring
• Testing REST with multiple MIME types
• Testing Web APIs with Postman Collections
• Spring Boot Consuming and Producing JSON

E-book

These articles are part of the Spring REST E-book:

1. Bootstrap a Web Application with Spring 5
2. Build a REST API with Spring and Java Config
3. Http Message Converters with the Spring Framework
4. Spring's RequestBody and ResponseBody Annotations
5. Entity To DTO Conversion for a Spring REST API
6. Error Handling for REST with Spring
7. REST API Discoverability and HATEOAS
8. An Intro to Spring HATEOAS
9. REST Pagination in Spring
10. Test a REST API with Java