vicly

Avoid duplicate form submission using PRG (Post/Redirect/Get)

If a user submits a form (POST), and then refresh, it may cause undesired result, e.g. duplicate web purchase.

While if a web user refreshes before the initial submission has completed because of server lag, resulting in a duplicate HTTP POST request in certain user agents.

Problem

Fix

vicly

@Entity
@Table(name = "product")
public class Product 
{
  @Id
  private String id;
  
  @Column(name = "visible")
  private boolean visible;

vicly

ID Token

• a JWT contains user profile information, e.g. user’s name, email, etc, represented in claims.

Access Token

• a credential used by an application to access a protected resource, e.g. API
• sent from client to server, server use information in the token to decide whether the client is authorised or not
• token has expired time
• must also be kept secret, but due to its shorter life, security considerations are less critical

vicly

1. Lambda stack exports lambda ARN
2. App stack defines log group
3. App stack defines subscription to the log group for lambda

So, by design, many app stacks share the same lambda stack to handle log events.

Stack

App Stack LogGroup

vicly

Create client

  private static AmazonKinesis setupKinesisClient()
  {
    AWSCredentialsProvider provider = new DefaultAWSCredentialsProviderChain();

    ClientConfiguration kinesisConfig = new ClientConfiguration();
    kinesisConfig.setMaxConnections(1);
 kinesisConfig.setProtocol(Protocol.HTTPS);

vicly

//  testCompile "junit:junit:4.12"
//  testCompile "org.assertj:assertj-core:3.5.2"
//  testCompile "com.github.tomakehurst:wiremock-standalone:2.7.1"

import static com.github.tomakehurst.wiremock.client.WireMock.aResponse;
import static com.github.tomakehurst.wiremock.client.WireMock.delete;
import static com.github.tomakehurst.wiremock.client.WireMock.equalTo;
import static com.github.tomakehurst.wiremock.client.WireMock.post;
import static com.github.tomakehurst.wiremock.client.WireMock.put;
import static com.github.tomakehurst.wiremock.client.WireMock.stubFor;

vicly

# OPS_PASSWORD are environment variables, need to export before running this command
# $ENV.json is a template, and OPS_PASSWORD as ${OPS_PASSWORD}
# parameters.json is the command output
envsubst '${OPS_PASSWORD},${DCS_PASSWORD},${SSM_PASSWORD},${SVOF_PASSWORD}' < $ENV.json > parameters.json 

vicly

public class Product {
  @Id
  private String id;

  @Column(name = "name", nullable = false)
  private String name;

 @ElementCollection(fetch = FetchType.LAZY) // 

vicly

Basic Concept

127.0.0.1 vs 0.0.0.0

127.0.0.1 is the loopback Internet protocol (IP) address also referred to as the localhost. The address is used to establish an IP connection to the same machine or computer being used by the end-user.

0.0.0.0 is a special IP which is "no particular address" (invalid/unknown/not-applicable).

0.0.0.0/0 : all IPs

vicly

save()

• can be called outside a trasnaction (not good), but should AVOID this, otherwise mapped entities will not be saved which causes data inconsistency.(only the primary entity gets saved unless we flush the session)
• primary object is saved ASAP, the mapped object will be saved when committing transaction or flush the session
• if object is in persist state, when calling save(), trigger SQL UPDATE, otherwise SQL INSERT
• e.g. start a tran; read a obj, modify obj, save(obj), commit tran;
• load object to persistent context, further change will be tracked and saved when transaction is committed

persist()

• similar to save()