HttpSession

What is HttpSession Server will create a independent HttpSession for each register user. What does HttpSeesion do When user first time visit the Servlet, the server will create a independent Session for user. And generate an Session ID. This Session ID could be stored in explorer’s cookie. When user visit this Servlet next time, the …

@RequestMapping, @GetMapping and @PostMapping in Spring

@RequestMapping Originally, Spring had only @RequestMapping annotation for mapping all the incoming HTTP request URLs to the corresponding controller methods. @RequestMapping(value = "/users", method = RequestMethod.GET) public Users getUsers() { } @RequestMapping(value = "/users", method = RequestMethod.POST) public User createUser(User user) { } @RequestMapping(value = "/users/{id}", method = RequestMethod.GET) public User getUser(@PathVariable("id") String id) { …

The Spring @Controller and @RestController Annotations

@Controller We can annotate classic controllers with the @Controller annotation. This is simply a specialization of the @Component class, which allows us to auto-detect implementation classes through the classpath scanning. We typically use @Controller in combination with a @RequestMapping annotation for request handling methods. @Controller @RequestMapping("books") public class SimpleBookController { @GetMapping("/{id}", produces = "application/json") public …

How to convert Array to List

Plain Java public void givenUsingCoreJava_whenArrayConvertedToList_thenCorrect() { Integer[] sourceArray = { 0, 1, 2, 3, 4, 5 }; List<Integer> targetList = Arrays.asList(sourceArray); } Commons Collection public void givenUsingCommonsCollections_whenArrayConvertedToList_thenCorrect() { Integer[] sourceArray = { 0, 1, 2, 3, 4, 5 }; List<Integer> targetList = new ArrayList<>(6); CollectionUtils.addAll(targetList, sourceArray); } Guava public void givenUsingGuava_whenListConvertedToArray_thenCorrect() { List<Integer> sourceList = …

Hello World in Spring Boot

Build Maven Porject in Intellij Edit POM <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>myproject</artifactId> <version>0.0.1-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.6.1</version> </parent> <!– Additional lines to be added here… –> Adding Classpath Dependencies <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> </dependencies> Write Main and Controller Run Program

Quick Sort

QuickSort is a Divide and Conquer algorithm. It picks an element as pivot and partitions the given array around the picked pivot. There are many different versions of quickSort that pick pivot in different ways. Always pick first element as pivot. Always pick last element as pivot (implemented below) Pick a random element as pivot. …