In JavaScript, we can use forEach(function) to loop an Array. The provided function in forEach() will run once for each array element. var total = 0; var num = [1, 2, 3, 4, 5]; num.forEach(anyFunction) function anyFunction(data){ total += data; } console.log(total); //15 var words = ""; var num = ["a", "b", "c", "d", "e"]; […]
Some log4j2.xml examples, just for self-reference P.S Tested with Log4j 2.11.2 1. ConsoleAppender Logs to console. log4j2.xml <?xml version="1.0" encoding="UTF-8"?> <Configuration status="DEBUG"> <Appenders> <Console name="LogToConsole" target="SYSTEM_OUT"> <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} – %msg%n"/> </Console> </Appenders> <Loggers> <!– avoid duplicated logs with additivity=false –> <Logger name="com.mkyong" level="debug" additivity="false"> <AppenderRef ref="LogToConsole"/> </Logger> <Root level="error"> <AppenderRef ref="LogToConsole"/> </Root> […]
In JavaScript, we can combine indexOf() and splice() to remove a certain element from an Array. var array = [1, 2, 3, 4, 5]; console.log(array) // I want remove num 4, find the index first, -1 if it is not present. var index = array.indexOf(4); if (index > -1) { // found array.splice(index, 1); } […]
Enable the log4j 2 loggers to asynchronous, but hits the following order : $ mvn -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -jar app.jar java.lang.NoClassDefFoundError: com/lmax/disruptor/EventTranslatorVararg at java.lang.ClassLoader.defineClass1 (Native Method) at java.lang.ClassLoader.defineClass (ClassLoader.java:1009) at java.security.SecureClassLoader.defineClass (SecureClassLoader.java:174) at java.net.URLClassLoader.defineClass (URLClassLoader.java:545) at java.net.URLClassLoader.access$100 (URLClassLoader.java:83) at java.net.URLClassLoader$1.run (URLClassLoader.java:453) Solution To fix it, add disruptor pom.xml <dependency> <groupId>com.lmax</groupId> <artifactId>disruptor</artifactId> <version>3.4.2</version> </dependency> Note Read this Making […]
In JavaScript, we can use either location.replace() or location.href to redirect a page. Normally, we use location.replace() to simulate an HTTP redirect. <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> </head> <body> <h1>JavaScript – How to redirect a page</h1> <h3>1. location.replace</h3> <button onclick="httpRedirect()">location.replace</button> <h3>2. location.href</h3> <button onclick="mouseClick()">location.href</button> <script> // Simulate an HTTP redirect function httpRedirect() { location.replace("https://www.mkyong.com") […]
A simple log4j 2 hello world example. Tested with Log4j 2.11.2 Maven 3 Java 8 Note Apache Log4j 2, the fastest Java logging framework, provides significant improvements over its predecessor, Log4j 1.x. 1. Project Directory 2. Maven <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-api</artifactId> <version>2.11.2</version> </dependency> <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-core</artifactId> <version>2.11.2</version> </dependency> 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 […]
This article shows how to use Spring Web MVC to create REST endpoints for CRUD database operations using the Spring Data JPA and PostgreSQL. At the end of the tutorial, we will use Docker to start a PostgreSQL container to test the Spring Boot REST endpoints using curl commands. We will use Spring Test and […]
Spring Boot + Spring Data JPA + MySQL, and hits the following error message when the application starts : Tested with : Spring Boot 2.1.2.RELEASE mysql-connector-java 8.0.13 Hibernate 5.3.7 java.sql.SQLSyntaxErrorException: Table ‘DB_NAME.hibernate_sequence’ doesn’t exist at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:974) at com.mysql.cj.jdbc.ClientPreparedStatement.executeQuery(ClientPreparedStatement.java:1024) at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeQuery(ProxyPreparedStatement.java:52) at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeQuery(HikariProxyPreparedStatement.java) at org.hibernate.id.enhanced.TableStructure.executeQuery(TableStructure.java:216) at org.hibernate.id.enhanced.TableStructure.access$300(TableStructure.java:46) application.properties spring.datasource.url=jdbc:mysql://localhost:3306/test spring.datasource.username=mkyong […]
In JavaScript, we can use the classic indexOf() or the new ES6 includes to check if a String contains a substring. // old school, classic way var str = "mkyong"; if (str.indexOf(‘yo’) > -1) { // returns `-1` if it is not present. console.log(‘match’) // display this } else { console.log(‘not found’) } // ES6 […]
This article shows how to use Spring Web MVC to create REST endpoints to perform CRUD database operations using the Spring Data JPA and MySQL. At the end of the tutorial, we will use Docker to start a MySQL container to test the Spring Boot REST endpoints using curl commands. We will use Spring Test […]
This article shows how to use Spring Data JPA to perform CRUD operation into a H2 in-memory database. Technologies used: Spring Boot 3.1.2 Spring Data JPA (Hibernate 6 is the default JPA implementation) H2 in-memory database Maven Java 17 Table of contents: 1. Project Directory 2. Project Dependencies 3. Spring Data JPA – Entity 4. […]
Java JDBC PreparedStatement example to create a SQL IN condition. 1. PreparedStatement + Array In JDBC, we can use createArrayOf to create a PreparedStatement IN query. @Override public List<Integer> getPostIdByTagId(List<Integer> tagIds) { List<Integer> result = new ArrayList<>(); String sql = "SELECT tr.object_id as post_id FROM wp_term_relationships tr " + " JOIN wp_term_taxonomy tt JOIN wp_terms […]
In Java 8, we can use .toArray() to convert a Stream into an Array. 1. Stream -> String[] StreamString.java package com.mkyong; import java.util.Arrays; public class StreamString { public static void main(String[] args) { String lines = "I Love Java 8 Stream!"; // split by space, uppercase, and convert to Array String[] result = Arrays.stream(lines.split("\\s+")) .map(String::toUpperCase) […]
After some SQL queries, the system is unable to get any connection from the HikariPool and prompts the following error message HikariPool-1 – Connection is not available, request timed out after 30002ms. Tested with HikariCP 3.3.1 mysql-connector-java 5.1.47 Java 8 1. Solution 1.1 Enable the debug logs for com.zaxxer.hikari, it will print out many useful […]
The key is boxed() the IntStream into a Stream<Integer>, then only convert to an Array. StreamExample.java package com.mkyong; import java.util.Arrays; import java.util.stream.IntStream; import java.util.stream.Stream; public class StreamExample { public static void main(String[] args) { //int[] -> IntStream -> Stream<Integer> -> Integer[] int[] num = {3, 4, 5}; //1. int[] -> IntStream IntStream stream = Arrays.stream(num); […]
Few Java examples to declare, initialize and manipulate Array in Java 1. Declares Array 1.1 For primitive types. ArrayExample1.java package com.mkyong; import java.util.Arrays; public class ArrayExample1 { public static void main(String[] args) { //declares an array of integers int[] num1 = new int[5]; int[] num2 = {1, 2, 3, 4, 5}; int[] num3 = new […]
In this article, we will show you how to use YAML instead of properties file in Spring Boot. Tested with : Spring Boot 2.1.2.RELEASE Maven 3 Snakeyaml:jar:1.23 In short, create a application.yml in the src/resources folder, Spring Boot will load and parse .yml file automatically and bind the values into the classes which annotated with […]
In Spring Boot, we can create a CommandLineRunner bean to run code when the application is fully started. StartBookApplication.java package com.mkyong; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.Bean; import java.util.Arrays; import java.util.Comparator; import java.util.List; import java.util.stream.Collectors; @SpringBootApplication public class StartBookApplication { public static void main(String[] args) { SpringApplication.run(StartBookApplication.class, args); } // Injects […]
Few examples to show you how to sort a List with stream.sorted() 1. List 1.1 Sort a List with Comparator.naturalOrder() package com.mkyong.sorted; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamApplication { public static void main(String[] args) { List<String> list = Arrays.asList("9", "A", "Z", "1", "B", "Y", "4", "a", "c"); /* List<String> sortedList = list.stream() […]
This article shows a shell script to backup or export a MySQL / MariaDB database, gzip the exported file, and upload the gzipped backup file to Amazon S3. Table of contents 1. Install AWS CLI 2. Backup MySQL/MariaDB database to S3 (Shell Script) 3. How to run the backup script? 4. Run the backup script […]
In this article, we will show you how to test the Spring Boot REST application. Normally, we use the MockMvc or TestRestTemplate for the integration test. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Maven 3 Java 8 pom.xml <!– spring integration test –> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!– spring integration test for security–> […]
In Spring, we can use Hamcrest APIs like hasItem and hasSize to test a JSON Array. Review the following example : package com.mkyong; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.boot.test.mock.mockito.MockBean; import org.springframework.http.HttpHeaders; import org.springframework.http.MediaType; import org.springframework.test.context.ActiveProfiles; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.servlet.MockMvc; import static org.hamcrest.Matchers.*; import static org.mockito.ArgumentMatchers.any; import static org.mockito.Mockito.times; import […]
Try to mock a repository save() method, but it is always returning null? P.S Tested with Spring Boot 2 + Spring Data JPA @Test public void save_book_OK() throws Exception { Book newBook = new Book(1L, "Mockito Guide", "mkyong"); when(mockRepository.save(newBook)).thenReturn(newBook); mockMvc.perform(post("/books") .content("{json}") .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON)) .andExpect(status().isCreated()); } Solution 1. Mockito uses the equals for argument matching, try […]
In Java, you can use String.valueOf() to convert an Integer to String. 1. String.valueOf 1.1 Example to convert an Integer or int 10 to a String. Integer num = 10; //int num = 10; String numInString = String.valueOf(num); System.out.println(numInString); Output 10 2. toString() It works on Integer object only. Integer num = 10; String numInString […]
In Spring Boot, we can create a @TestConfiguration class to initialize some beans for testing class only. P.S Tested with Spring Boot 2 1. @TestConfiguration + @Import This @TestConfiguration class will not pick up by the component scanning, we need to import it manually. TestConfig.java package com.mkyong; import org.springframework.boot.test.context.TestConfiguration; import org.springframework.boot.web.client.RestTemplateBuilder; import org.springframework.context.annotation.Bean; import java.time.Duration; […]
In Java, we use equals() to compare string value. String str1 = "apple"; // compare strings case-sensitive if (str1.equals("apple")) { System.out.println("I have an apple."); } String str2 = "apple"; // compare strings case-insensitive if (str2.equalsIgnoreCase("APPLE")) { System.out.println("I have an APPLE."); } Output Terminal I have an apple. I have an APPLE. In this article, we […]
Try to mock a repository findById method, but no idea use thenReturn() to return an object, as it accepts an Optional? P.S Tested in Spring Boot 2 environment import static org.mockito.Mockito.*; import org.springframework.boot.test.mock.mockito.MockBean; @MockBean private BookRepository mockRepository; @Before public void init() { Book book = new Book(1L, "A Book"); //error, can’t resolve method thenReturn(book)? when(mockRepository.findById(1L)).thenReturn(book); […]
In this article, we will show you error handling in Spring Boot REST application. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Maven 3 Java 8 1. /error 1.1 By default, Spring Boot provides a BasicErrorController controller for /error mapping that handles all errors, and getErrorAttributes to produce a JSON response with details of the […]
In Java, we can use JSONAssert to unit test JSON data easily. 1. Maven pom.xml <dependency> <groupId>org.skyscreamer</groupId> <artifactId>jsonassert</artifactId> <version>1.5.0</version> </dependency> 2. JSON Object To test the JSON Object, Strict or not, fields order does not matter. If the extended fields are matter, enable the strict mode. 2.1 When the strictMode is off. JSONObject actual = […]
In this article, we will enhance the previous Spring REST Validation Example, by adding Spring Security to perform authentication and authorization for the requested URLs (REST API endpoints) Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Spring Security 5.1.3.RELEASE Spring Data JPA 2.1.4.RELEASE H2 In-memory Database 1.4.197 Tomcat Embed 9.0.14 JUnit 4.12 Maven 3 Java […]
Send a GET request with username and password, but hits the password encoder error? Tested Spring Boot 2.1.2.RELEASE 5.1.3.RELEASE $ curl localhost:8080/books -u user:password { "timestamp":"2019-02-22T15:03:49.322+0000", "status":500, "error":"Internal Server Error", "message":"There is no PasswordEncoder mapped for the id \"null\"", "path":"/books" } errors in logs java.lang.IllegalArgumentException: There is no PasswordEncoder mapped for the id "null" Here […]
Spring Boot integeration test, but unable to @Autowired MockMvc P.S Tested with Spring Boot 2.1.2.RELEASE BookControllerTest.java package com.mkyong; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.http.MediaType; import org.springframework.security.test.context.support.WithMockUser; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.servlet.MockMvc; import static org.hamcrest.Matchers.is; import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get; import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print; import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT) public class BookControllerTest { @Autowired […]
In this article, we will enhance the previous Spring REST Hello World example, by adding bean validation and custom validator. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Maven 3 Java 8 1. Controller Review the previous REST Controller again : BookController.java package com.mkyong; import com.mkyong.error.BookNotFoundException; import com.mkyong.error.BookUnSupportedFieldPatchException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.util.StringUtils; import org.springframework.web.bind.annotation.*; import […]
In this article, we will show you how to develop a Spring Boot REST style web service to handle CRUD operations from a H2 In-memory database. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Spring Data JPA 2.1.4.RELEASE H2 In-memory Database 1.4.197 Tomcat Embed 9.0.14 JUnit 4.12 Maven 3 Java 8 1. Project Directory 2. […]
Run the following Spring Boot + JUnit 5 + Mockito integration test. package com.mkyong.core.services; import com.mkyong.core.repository.HelloRepository; import org.junit.jupiter.api.BeforeEach; import org.junit.jupiter.api.DisplayName; import org.junit.jupiter.api.Test; import org.mockito.InjectMocks; import org.mockito.Mock; import org.springframework.boot.test.context.SpringBootTest; import static org.junit.jupiter.api.Assertions.assertEquals; import static org.mockito.Mockito.when; @SpringBootTest public class HelloServiceMockTest { @Mock private HelloRepository helloRepository; @InjectMocks // auto inject helloRepository private HelloService helloService = new HelloServiceImpl(); @BeforeEach […]
In this article, we will show you how to do Spring Boot 2 integration test with JUnit 5, and also Mockito. Spring Boot 2.1.2.RELEASE JUnit 5 Mockito 2 Maven 3 In short, exclude junit4 from spring-boot-starter-test, and include the JUnit 5 jupiter engine manually, done. Let see the following Spring boot MVC web application, and […]
In this article, we will show you how to develop a reactive web application, using Server-sent events Spring Boot 2.1.2.RELEASE Spring WebFlux 5.1.4.RELEASE Thymeleaf 3.0.11.RELEASE JUnit 5.3.2 Maven 3 In Spring, returns JSON and header MediaType.TEXT_EVENT_STREAM_VALUE @RestController public class CommentController { @GetMapping(path = "/comment/stream", produces = MediaType.TEXT_EVENT_STREAM_VALUE) public Flux<Comment> feed() { //… } } In […]
In this article, we will show you how to develop a reactive web application. Spring Boot 2.1.2.RELEASE Spring WebFlux 5.1.4.RELEASE Thymeleaf 3.0.11.RELEASE Maven 3 Spring Boot will configure everything, and the key is using the Thymeleaf ReactiveDataDriverContextVariable to enable the data-driven mode in Thymeleaf template. @RequestMapping("/") public String index(final Model model) { // data streaming, […]
Live patching is slowly catching on, but not for the reasons you might think. In this article, I’ll explain what Linux kernel live patching is, what it isn’t, what services there are, who might use it and why. I’ll show the basic installation steps for Livepatch (on Ubuntu), Kpatch (on Red Hat), and one other, […]
The Java project is using log4j2, but look like some components are used SLF4J logging and caused the following error message: SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details. Solution To fix it, we need a SLF4J Bridge. Puts log4j-slf4j-impl in the classpath. pom.xml […]
