Skip to content

Category: Spring Boot

JPA native queries with eager fetch and @SqlResultMapping

Published on March 27, 2024

JPA supports eager and lazy fetch of child entities. If you’re not careful with the lazy fetch strategy it can result in excessive queries as it needs to execute a query for the parent entity and then an additional one for each child. This is the so-called n+1 problem. You’ll often want to use eager fetching so that you can pull the parent and all children with a single query.

If you use HQL/JPQL, the JPA Criteria API or queries derived from Spring Data Repository method names, JPA will convert your SQL query result set to entity objects. That’s what an Object Relational Mapping (ORM) system is for. However if you use JPA native queries (SQL), you’ll need to map the results yourself.

In this post, I’ll look at how to run eager fetches for JPQL and native queries and how to manage the results.

Continue readingJPA native queries with eager fetch and @SqlResultMapping

Spring4Shell

Published on April 4, 2022

The Spring4Shell (CVE-2022-22965) critical severity vulnerability in Spring Framework allows remote code execution (RCE). At time of writing, it can be exploited only in very specific scenarios. However, Spring have made a patch available (Spring Framework version 5.3.18 and 5.2.20) and I strongly advise you to take them, even if you’re not running the exploitable setup.

Continue readingSpring4Shell

Spring Security delegating password encoder

Published on March 14, 2022

The Spring Security PasswordEncoder interface exists to make it easy to safely encode passwords for storage in a database. Hashing the password using a secure algorithm with a heavy work factor will slow down an attacker even if they compromise the password database.

Since the interface was introduced, security recommendations have changed as CPUs / GPUs become more powerful and as vulnerabilities are discovered in legacy algorithms. The original StandardPasswordEncoder is now deprecated as the SHA-256 algorithm is considered insecure. Spring offers more secure implementations based on bcrypt, PBKDF2 and Argon2.

However, Spring no longer ties you to a single algorithm. The new DelegatingPasswordEncoder provides support for multiple PasswordEncoder implementations, many of which are available in Spring Boot applications with default configuration. This makes it possible to select an algorithm at run time and to have a database containing password hashes with different algorithms.

Continue readingSpring Security delegating password encoder

Deploying to Google Kubernetes Engine

Published on March 15, 2020

Previously we looked at building a Spring Cloud Data Flow on Kubernetes. As a follow up, we’re now looking at deploying to Google Kubernetes Engine. The great thing about Kubernetes you use exactly the same commands to manage a cluster on your laptop as on a server or cloud compute platform. Google has first class support for Kubernetes on the Google Kubernetes Engine so deploying the Primer application was very straightforward.

Continue readingDeploying to Google Kubernetes Engine

Spring Cloud Data Flow on Kubernetes

Published on February 29, 2020

Spring Cloud Data Flow is a powerful tool for composing and deploying message driven data pipelines. It allows us to compose simple Spring Cloud Stream applications into complex processing pipelines. It also takes care of deploying these pipelines into Kubernetes or into Cloud Foundry.

It’s powerful but has a lot of moving parts. It can be daunting to get a simple pipeline running. This article introduces the Primer demo for SCDF and describes how to deploy it into Kubernetes on a local development machine.

Continue readingSpring Cloud Data Flow on Kubernetes

Thymeleaf and Spring Security

Published on June 29, 2017

Thymeleaf is a popular templating engine, particularly with Spring projects. Spring Boot has chosen Thymeleaf as the view technology of choice, largely replacing the need for JSP. With old JSPs, custom tag libraries provided integration with various technologies, including Spring Security. A similar library exists to integrate Thymeleaf and Spring Security – the Thymeleaf Spring Security Integration module.

Continue readingThymeleaf and Spring Security

Spring Boot Actuator Trace: Logging HTTP requests

Published on April 14, 2017

Spring Boot Actuator provides assistance for application monitoring. Out of the box it provides information on application health, configuration and logging. It’s trivial to enable: simply add the spring-boot-starter-actuator dependency to a Spring Boot project in Maven or Gradle and it just works! The monitoring information is provided as JSON from HTTP endpoints or via JMX.

The Spring Boot Actuator trace endpoint is particularly handy. By default it shows the last 100 HTTP requests made to the application. This article walks through an Actuator demo and shows some of the configuration options to get the best from this feature.

Continue readingSpring Boot Actuator Trace: Logging HTTP requests

Spring Boot as a Windows Service

Published on January 1, 2017

The documentation provided by Spring on deploying a Spring Boot application as a Windows Service is a little sparse. Indeed, here it is in full:

Spring Boot application can be started as Windows service using winsw.

A sample maintained separately to the core of Spring Boot describes step-by-step how you can create a Windows service for your Spring Boot application.

— From Spring Boot Reference Guide (version 1.4.3), section 56.2: Microsoft Windows Services

As the official reference guide is lacking detail, here is a step by step guide to building and deploying a Spring Boot application as a Windows Service.

Continue readingSpring Boot as a Windows Service

Microservice discovery with Spring Boot and Eureka

Published on September 12, 2016

One of the standard problems with Microservices Architecture is the issue of service discovery. Once we’ve decomposed our application into more than a handful of distinct microservices, it becomes difficult for every service to know the address of every other service it depends on. Configuring dependencies from inside a microservice is impractical – it distributes configuration among all the microservices. It also violates the DRY principle – multiple microservice instances will need access to the same configuration settings. What’s more, it goes against the Dependency Injection design that’s supposed to be one of the benefits of the Microservices Architecture.

The standard solution is to delegate location of microservices to a new microservice. In keeping with the Single Responsibility Principle, this ‘discovery’ microservice is responsible for tracking the locations of all the other microservices and nothing else.

Netflix’s Eureka is an implementation of a discovery server and integration is provided by Spring Boot. Using Spring Boot, we can build a Eureka discovery server and have our microservices register with it.

Continue readingMicroservice discovery with Spring Boot and Eureka