Upgrade to Java 21 (#305)

* upgrade to java 21

* adding a missing jacoco report dependency

* upgrading docker container to use Java 21

* downgrading to gradle 8.8 version to be in line with other places where gradle 8.8 is used

Author: ORybak5

docker/docker-compose.yml

@@ -1,4 +1,3 @@
-version: '3.8'
 services:
   integration-adaptor-111:
     build:

docker/service/Dockerfile

@@ -1,11 +1,11 @@
-FROM gradle:8.8-jdk17 AS build
+FROM gradle:8.8-jdk21-jammy AS build
 COPY --chown=gradle:gradle service /home/gradle/service
 
 WORKDIR /home/gradle/service
 
 RUN ./gradlew --build-cache bootJar
 
-FROM eclipse-temurin:17-jre-jammy
+FROM eclipse-temurin:21-jre-jammy
 
 EXPOSE 8081
 

nhs-england-developer-information.md

@@ -4,7 +4,7 @@
 > The audience of this documentation is designed for NHS England developers.
 
 ## Pre requisites for running the Adaptor:
-1. JDK 17
+1. JDK 21
 2. Docker
 
 ## How to run service:

service/build.gradle

@@ -13,6 +13,11 @@ apply plugin: 'org.springframework.boot'
 apply plugin: 'checkstyle'
 apply plugin: "com.github.spotbugs"
 
+java {
+    sourceCompatibility = JavaVersion.VERSION_21
+    targetCompatibility = JavaVersion.VERSION_21
+}
+
 repositories {
     mavenCentral()
     flatDir {