May 20th, 2023
Microservices with Modules(JPMS)
<!-- pom.xml in 6392_chapter2 -->
<?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>
<groupId>com.packtpub.mmj</groupId>
<artifactId>6392_chapter2</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>lib</module>
<module>rest</module>
</modules>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>9</maven.compiler.source>
<maven.compiler.target>9</maven.compiler.target>
<spring-boot-version>2.0.0.BUILD-SNAPSHOT</spring-boot-version>
<spring-version>5.0.0.BUILD-SNAPSHOT</spring-version>
<start-class>com.packtpub.mmj.rest.RestSampleApp</start-class>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.BUILD-SNAPSHOT</version>
</parent>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.pactkpub.mmj</groupId>
<artifactId>rest</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.packtpub.mmj</groupId>
<artifactId>lib</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.0.0.BUILD-SNAPSHOT</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<classifier>exec</classifier>
<mainClass>${start-class}</mainClass>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.9</source>
<target>1.9</target>
<showDeprecation>true</showDeprecation>
<showWarnings>true</showWarnings>
</configuration>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>https://repo.spring.io/snapshot</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>https://repo.spring.io/snapshot</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</project>
<!-- pom.xml in lib -->
<?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>com.packtpub.mmj</groupId>
<artifactId>6392_chapter2</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>lib</artifactId>
<packaging>jar</packaging>
<properties>
<exec.mainClass>com.packtpub.mmj.lib.Lib</exec.mainClass>
</properties>
</project>
// module-info.java in lib module
module com.packtpub.mmj.lib {
exports com.packtpub.mmj.lib.model to com.packtpub.mmj.rest;
opens com.packtpub.mmj.lib.model;
}
// Calculation.java
package com.packtpub.mmj.lib.model;
import java.util.List;
public class Calculation {
String function;
private List<String> input;
private List<String> output;
public Calculation(){
}
public Calculation(List<String> input, List<String> output, String function) {
this.function = function;
this.input = input;
this.output = output;
}
public List<String> getInput() {
return input;
}
public void setInput(List<String> input) {
this.input = input;
}
public List<String> getOutput() {
return output;
}
public void setOutput(List<String> output) {
this.output = output;
}
public String getFunction() {
return function;
}
public void setFunction(String function) {
this.function = function;
}
}
<!-- pom.xml in rest -->
<?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>com.packtpub.mmj</groupId>
<artifactId>6392_chapter2</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>rest</artifactId>
<packaging>jar</packaging>
<properties>
<exec.mainClass>com.packtpub.mmj.rest.Rest</exec.mainClass>
</properties>
<dependencies>
<dependency>
<groupId>com.packtpub.mmj</groupId>
<artifactId>lib</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
</project>
// module-info.java in rest module
module com.packtpub.mmj.rest {
requires spring.core;
requires spring.beans;
requires spring.context;
requires spring.aop;
requires spring.web;
requires spring.expression;
requires spring.boot;
requires spring.boot.autoconfigure;
requires com.packtpub.mmj.lib;
exports com.packtpub.mmj.rest;
exports com.packtpub.mmj.rest.resources;
opens com.packtpub.mmj.rest;
opens com.packtpub.mmj.rest.resources;
}
// CalculationController.java
package com.packtpub.mmj.rest.resources;
import com.packtpub.mmj.lib.model.Calculation;
import java.util.ArrayList;
import java.util.List;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("calculation")
public class CalculationController {
private static final String PATTERN = "^-?+\\d+\\.?+\\d*$";
@RequestMapping("/power")
public Calculation pow(@RequestParam(value = "base") String b, @RequestParam(value = "exponent") String e) {
List<String> input = new ArrayList();
input.add(b);
input.add(e);
List<String> output = new ArrayList();
String powValue;
if (b != null && e != null && b.matches(PATTERN) && e.matches(PATTERN)) {
powValue = String.valueOf(Math.pow(Double.valueOf(b), Double.valueOf(e)));
} else {
powValue = "Base or/and Exponent is/are not set to numeric value.";
}
output.add(powValue);
return new Calculation(input, output, "power");
}
@RequestMapping(value = "/sqrt/{value:.+}", method = RequestMethod.GET)
public Calculation sqrt(@PathVariable(value = "value") String aValue) {
List<String> input = new ArrayList<>();
input.add(aValue);
List<String> output = new ArrayList();
String sqrtValue;
if (aValue != null && aValue.matches(PATTERN)) {
sqrtValue = String.valueOf(Math.sqrt(Double.valueOf(aValue)));
} else {
sqrtValue = "Input value is not set to numeric value.";
}
output.add(sqrtValue);
return new Calculation(input, output, "sqrt");
}
}
//RestSampleApp.java
package com.packtpub.mmj.rest;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class RestSampleApp {
public static void main(String[] args) {
SpringApplication.run(RestSampleApp.class, args);
}
}
> mvn clean install
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for 6392_chapter2 1.0-SNAPSHOT:
[INFO]
[INFO] 6392_chapter2 ...................................... SUCCESS [ 0.725 s]
[INFO] lib ................................................ SUCCESS [ 1.216 s]
[INFO] rest ............................................... SUCCESS [ 0.806 s]
//While using JDK 16 and above, we get an error similar to this
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @198e2867
at java.base/java.lang.reflect.AccessibleObject.throwInaccessibleObjectException(AccessibleObject.java:387) ~[na:na]
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:363) ~[na:na]
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:311) ~[na:na]
at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:201) ~[na:na]
at java.base/java.lang.reflect.Method.setAccessible(Method.java:195) ~[na:na]
at org.springframework.cglib.core.ReflectUtils$1.run(ReflectUtils.java:61) ~[spring-core-5.0.4.RELEASE.jar!/:5.0.4.RELEASE]
at java.base/java.security.AccessController.doPrivileged(AccessController.java:569) ~[na:na]
at org.springframework.cglib.core.ReflectUtils.<clinit>(ReflectUtils.java:52) ~[spring-core-5.0.4.RELEASE.jar!/:5.0.4.RELEASE]
at org.springframework.cglib.core.KeyFactory$Generator.generateClass(KeyFactory.java:243) ~[spring-core-5.0.4.RELEASE.jar!/:5.0.4.RELEASE]
at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) ~[spring-core-5.0.4.RELEASE.jar!/:5.0.4.RELEASE]
at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329) ~[spring-core-5.0.4.RELEASE.jar!/:5.0.4.RELEASE]
... 33 common frames omitted
// use this code to run without the above errors
java --add-opens java.base/java.lang=ALL-UNNAMED -jar rest/target/rest-1.0-SNAPSHOT-exec.jar
// run the code on different port
java --add-opens java.base/java.lang=ALL-UNNAMED -Dserver.port=8083 -jar rest/target/rest-1.0-SNAPSHOT-exec.jar
http://localhost:8083/calculation/power?base=2&exponent=3
http://localhost:8083/calculation/sqrt/2
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