The following WebFilter redirects incoming requests for / to a static HTML file, index.html. ToIndexPageRedirection.java package com.hascode.tutorial; import org.springframework.stereotype.Component; import org.springframework.web.server.ServerWebExchange; import org.springframework.web.server.WebFilter; import org.springframework.web.server.WebFilterChain; import reactor.core.publisher.Mono; @Component public class ToIndexPageRedirection implements WebFilter { @Override public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) { if (exchange.getRequest().getURI().getPath().equals("/")) { return chain.filter( exchange.mutate().request( exchange.getRequest().mutate().path("/index.html").build() ).build() ); } return chain.filter(exchange); } } Ressources: JavaDocs WebFilter

Sometimes this is useful for the diagnosis of configuration and network problems of ones Java application. This is our single-class HTTP client example without the need for external dependencies: HttpTest.java import javax.net.ssl.KeyManagerFactory; import javax.net.ssl.SSLContext; import javax.net.ssl.TrustManagerFactory; import java.io.FileInputStream; import java.io.IOException; import java.net.InetSocketAddress; import java.net.ProxySelector; import java.net.URI; import java.net.URISyntaxException; import java.net.http.HttpClient; import java.net.http.HttpRequest; import java.net.http.HttpRequest.BodyPublishers; import java.net.http.HttpResponse; import java.net.http.HttpResponse.BodyHandlers; import java.security.KeyManagementException; import java.security.KeyStore; import java.security.KeyStoreException; import java.security.NoSuchAlgorithmException; import java.security.UnrecoverableKeyException; import java.security.cert.CertificateException; import java.time.Duration; import java.time.temporal.ChronoUnit; public class HttpTest { public static void main(String[] args) throws URISyntaxException, NoSuchAlgorithmException, KeyManagementException, KeyStoreException, UnrecoverableKeyException, IOException, CertificateException { String bodyPayload = """ ourpayload, json, xml, ... """; String keyStorePath = "/opt/keystore.jks"; String keyStorePassword = "ABCDEFG"; String proxyHost = "ourproxy.proxy"; String uriString = "https://some-service/api"; int proxyPort = 8080; int timeoutInSeconds = 60; KeyStore keyStore = KeyStore.getInstance("JKS"); keyStore.load(new FileInputStream(keyStorePath), keyStorePassword.toCharArray()); KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance("PKIX"); keyManagerFactory.init(keyStore, null); TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance("PKIX"); // using same keystore for both trustManagerFactory.init(keyStore); SSLContext sslContext = SSLContext.getInstance("TLS"); sslContext.init(keyManagerFactory.getKeyManagers(), trustManagerFactory.getTrustManagers(), null); HttpClient client = HttpClient.newBuilder() .proxy( ProxySelector.of(new InetSocketAddress(proxyHost, proxyPort))) .sslContext(sslContext) .build(); URI uri = new URI(uriString); HttpRequest request = HttpRequest.newBuilder(uri) .POST(BodyPublishers.ofString(bodyPayload)) .timeout(Duration.of(timeoutInSeconds, ChronoUnit.SECONDS)) .build(); System.out.printf("Sending POST request to %s, timeout: %ds%n", uri, timeoutInSeconds); try { HttpResponse response = client.send(request, BodyHandlers.ofString()); System.out.println("Response received..."); System.out.printf("\tResponse-Status: %d%n", response.statusCode()); System.out.printf("\tResponse-Body: %s%n", response.body()); System.out.println("-------------------------------------%n"); } catch (IOException e) { System.err.printf("IOException caught: %s%n", e.getMessage()); e.printStackTrace(System.err); } catch (InterruptedException e) { System.err.printf("IOException caught: %s%n", e.getMessage()); e.printStackTrace(System.err); } } } ...

Let’s say we would like to increase the limit t 10MB …​ Broker Configuration Apply the new limit either by modifying the server.properties like this…​ max.message.bytes=10485760 or apply it to a specific topic using kafka-configs.sh --bootstrap-server localhost:9092 \ --entity-type topics \ --entity-name thetopic \ --alter \ --add-config max.message.bytes=10485760 Producer Configuration for Spring Boot We simply need to add the following line to our application.properties: spring.kafka.producer.properties.max.request.size=spring.kafka.producer.properties.max.request.size The following proof-of-concept demonstrates that without the property, sending a large message fails, with the property it succeeds: ...

Sometimes it is nice to set up an embedded Kafka broker for testing without the need to have Docker installed (e.g. for using testcontainers-lib). The following snippet shows, how to set up an embedded Kafka instance for testing for a Spring Boot project. Setup Using Maven, this is our Spring Boot project with dependencies needed: pom.xml <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId>(1) <version>2.6.4</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.hascode.tutorial</groupId> <artifactId>kafka-testing</artifactId> <version>1.0.0-SNAPSHOT</version> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>17</java.version> <maven.compiler.source>${java.version}</maven.compiler.source> <maven.compiler.target>${java.version}</maven.compiler.target> <kafka.version>3.1.0</kafka.version>(2) </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.kafka</groupId> <artifactId>spring-kafka</artifactId>(3) </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.kafka</groupId> <artifactId>spring-kafka-test</artifactId>(4) <scope>test</scope> </dependency> <dependency>(5) <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-api</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-engine</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.junit.platform</groupId> <artifactId>junit-platform-launcher</artifactId> <scope>test</scope> </dependency> [..] </project> ...

This Linkchecker claims to be way faster than blc and wummel/linkchecker. Using Docker, we may validate our site’s links in no time and without complex setup. docker run --rm tennox/linkcheck hascode.io Resources https://github.com/filiph/linkcheck

MapStruct is a nice tool to generate mappers for converting one Java bean into another e.g. for projections, data-transfer-objects and so on …​ As long as fields in source and target beans do match, the mapper is able to generate the data setting automatically .. else we may specify which source fields to map into which target fields or to register custom converters with ease. Using Maven, we need to add dependencies and plugin integration to our pom.xml: ...

Sometimes when accessing SOAP APIs, our SOAP client needs to sign the request. How this can be achieved using Spring Boot’s WebserviceTemplate within a few steps is the scope of this short article. This snippet only deals with the client side not with the security configuration on the server side. Also it assumes, that you have already set up your keystore/truststore and that you’re loading these with your Spring Boot application’s startup without errors. ...

Steps Pull image and run with ports exposed: docker run --name "nifi" -p 8443:8443 -d apache/nifi:latest Fetch the generated username and password from the logs: docker logs nifi | grep -A1 "Generated Username" Generated Username [8f6d91f7-733e-40cf-b900-059ea9dccbf2] Generated Password [v7KGiiRYLJL2+HzhKOqz1rbgiPOaWz0B] Now we may enter the https://localhost:8443/nifi/login in our browser, accept the security exemption and login with the credentials from above, voila! Installing additional connectors I have found a nice summary on the following GitHub repository: ...

A simple setup when two Postgres databases prefilled with schema/data needed. docker-compose.yml version: '3.6' services: postgres1: image: postgres restart: always environment: - DATABASE_HOST=127.0.0.1 - POSTGRES_USER=root - POSTGRES_PASSWORD=root - POSTGRES_DB=root ports: - "15432:15432" volumes: - ./postgres1-init.sql:/docker-entrypoint-initdb.d/docker_postgres_init.sql postgres2: image: postgres restart: always environment: - DATABASE_HOST=127.0.0.1 - POSTGRES_USER=root - POSTGRES_PASSWORD=root - POSTGRES_DB=root ports: - "25432:25432" volumes: - ./postgres2-init.sql:/docker-entrypoint-initdb.d/docker_postgres_init.sql And our sample init scripts: CREATE USER tester WITH PASSWORD 'tester' CREATEDB; CREATE DATABASE testdb WITH OWNER = tester ENCODING = 'UTF8' LC_COLLATE = 'en_US.utf8' LC_CTYPE = 'en_US.utf8' TABLESPACE = pg_default CONNECTION LIMIT = -1; ...

Sometimes one needs to derive a Google Protocol Buffers schema from an XML schema .. e.g. from an Enterprise Architect Export. Tool used here: schema2proto (GitLab project) Steps Download schema2proto-lib from the global Maven repository: https://search.maven.org/search?q=schema2proto Run Schema2Proto against a give XSD schema file and with a given output directory: java -jar schema2proto-lib-1.53.jar Schema2Proto --outputDirectory=src/main/protobuf input.xsd A yaml config file may be given instead of cli parameters: java -jar schema2proto-lib-1.53.jar Schema2Proto ----configFile=config.yaml input.xsd ...