Quick Intro to Maven

Transcript

1. Quick Start to Maven
2. Build Tools • Ant (2000) • One of the first "modern" build tools • Very popular among Java • Easy, uses procedural programming idea • Uses XML which is not very good on the concept of procedural programming • XML can began to be very big • Maven (2004) • Uses also XML, but structure is different • Relies conventions and provides available targets (goals) • Has repository support (dependencies) • Gradle (2007) • Uses DSL instead of XML
3. Convention over Configuration • Developers are not required to create build process • Maven offers sensible default behavior for projects • Maven creates a default project structure • Developer adds files to directories and writes configuration to pom.xml
4. Default Project Structure Item Default source code src/main/java resources src/main/resources tests src/test jar target/ byte code target/classes
5. pom.xml • POM, Project Object Model, is an xml file • Base directory of your project • Information about the project and compiling process • Defines dependencies • The pom.xml can inherit a super pom, which provides basic configuration
6. pom.xml <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/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.company</groupId> <artifactId>myapp</artifactId> <packaging>jar</packaging> <version>1.0-BETA</version> <properties> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> </project> artifact is a file and each artifact has a group id, usually like package in Java. Also version is defined. GroupId + artifactId + version creates uniquely identified artifact. Project's dependencies are specified as artifacts
7. Project Structure . ├── pom.xml └── src └── main └── java └── com └── company └── Main.java
8. Main.java package com.company; public class Main { public static void main(String [] args) { System.out.println("Hello World"); } }
9. Commands • To compile • mvn compile • To test (using JUnit) • mvn test • Create jar file • mvn package • To remove target • mvn clean • To run • mvn exec:java -Dexec.mainClass="com.company.Main" • To create Eclipse project • mvn eclipse:eclipse
10. Easier Running with plug-in: mvn exec:java <build> <plugins> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>exec-maven-plugin</artifactId> <version>1.5.0</version> <configuration> <mainClass>com.company.Main</mainClass> <cleanupDaemonThreads>false</cleanupDaemonThreads> </configuration> </plugin> </plugins> </build>
11. Main – class for jar <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-jar-plugin</artifactId> <version>3.0.2</version> <configuration> <archive> <manifest> <mainClass>com.company.Main</mainClass> </manifest> </archive> </configuration> </plugin>
12. public class Main { public static void main(String [] args) { try { String data = makeHttpRequest("https://jsonplaceholder.typicode.com/todos/"); System.out.println(data); } catch(URISyntaxException | IOException | InterruptedException e) { e.printStackTrace(); } } public static String makeHttpRequest(String url) throws URISyntaxException, IOException, InterruptedException { HttpClient client = HttpClient.newHttpClient(); HttpRequest request = HttpRequest.newBuilder() .uri(new URI(url)) .build(); HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString()); return response.body(); } } Uses HttpClient to make http request
13. JSON Parsing ... import org.json.*; public class Main { public static void main(String [] args) { try { String data = makeHttpRequest("https://jsonplaceholder.typicode.com/todos/"); // Output the first title JSONArray allTodos = new JSONArray(data); JSONObject todo = allTodos.getJSONObject(0); System.out.println(todo.getString("title")); } catch(URISyntaxException | IOException | InterruptedException e) { e.printStackTrace(); } } Will Fail! This is not part of java se!
14. Dependency to pom.xml <dependencies> <dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20190722</version> </dependency> </dependencies>
15. Location of downloaded jars • In Unix/Mac • ~/.m2 • In Windows • C:\Documents and Settings\{user-name}\.m2