BAEL-1200 JavaPoet (#4500)

* Initial commit

* Implement JavaPoet examples

libraries/src/test/java/com/baeldung/javapoet/test/PersonGeneratorUnitTest.java

@@ -0,0 +1,99 @@
+package com.baeldung.javapoet.test;
+
+import com.baeldung.javapoet.PersonGenerator;
+import org.apache.commons.io.FileUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+@RunWith(JUnit4.class)
+public class PersonGeneratorUnitTest {
+
+    private PersonGenerator generator;
+    private Path generatedFolderPath;
+    private Path expectedFolderPath;
+
+    @Before
+    public void setUp() {
+        String packagePath = this
+          .getClass()
+          .getPackage()
+          .getName()
+          .replace(".", "/") + "/person";
+        generator = new PersonGenerator();
+        generatedFolderPath = generator
+          .getOutputPath()
+          .resolve(packagePath);
+        expectedFolderPath = Paths.get(new File(".").getAbsolutePath() + "/src/test/java/" + packagePath);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        FileUtils.deleteDirectory(new File(generator
+          .getOutputPath()
+          .toUri()));
+    }
+
+    @Test
+    public void whenGenerateGenderEnum_thenGenerateGenderEnumAndWriteToFile() throws IOException {
+        generator.generateGenderEnum();
+        String fileName = "Gender.java";
+        assertThatFileIsGeneratedAsExpected(fileName);
+        deleteGeneratedFile(fileName);
+    }
+
+    @Test
+    public void whenGeneratePersonInterface_thenGeneratePersonInterfaceAndWriteToFile() throws IOException {
+        generator.generatePersonInterface();
+        String fileName = "Person.java";
+        assertThatFileIsGeneratedAsExpected(fileName);
+        deleteGeneratedFile(fileName);
+    }
+
+    @Test
+    public void whenGenerateStudentClass_thenGenerateStudentClassAndWriteToFile() throws IOException {
+        generator.generateStudentClass();
+        String fileName = "Student.java";
+        assertThatFileIsGeneratedAsExpected(fileName);
+        deleteGeneratedFile(fileName);
+    }
+
+    private void assertThatFileIsGeneratedAsExpected(String fileName) throws IOException {
+        String generatedFileContent = extractFileContent(generatedFolderPath.resolve(fileName));
+        String expectedFileContent = extractFileContent(expectedFolderPath.resolve(fileName));
+
+        assertThat("Generated file is identical to the file with the expected content", generatedFileContent, is(equalTo(expectedFileContent)));
+
+    }
+
+    private void deleteGeneratedFile(String fileName) throws IOException {
+        Path generatedFilePath = generatedFolderPath.resolve(fileName);
+        Files.delete(generatedFilePath);
+    }
+
+    private String extractFileContent(Path filePath) throws IOException {
+        byte[] fileContentAsBytes = Files.readAllBytes(filePath);
+        String fileContentAsString = new String(fileContentAsBytes, StandardCharsets.UTF_8);
+
+        if (!fileContentAsString.contains("\r\n")) {
+            // file is not in DOS format
+            // convert it first, so that the content comparison will be relevant
+            return fileContentAsString.replaceAll("\n", "\r\n");
+        }
+        return fileContentAsString;
+    }
+
+}

libraries/src/test/java/com/baeldung/javapoet/test/person/Gender.java

@@ -0,0 +1,9 @@
+package com.baeldung.javapoet.test.person;
+
+public enum Gender {
+    MALE,
+
+    FEMALE,
+
+    UNSPECIFIED
+}

libraries/src/test/java/com/baeldung/javapoet/test/person/Person.java

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+package com.baeldung.javapoet.test.person;
+
+import java.lang.String;
+
+public interface Person {
+    String DEFAULT_NAME = "Alice";
+
+    String getName();
+
+    default String getDefaultName() {
+        return DEFAULT_NAME;
+    }
+}

libraries/src/test/java/com/baeldung/javapoet/test/person/Student.java

@@ -0,0 +1,37 @@
+package com.baeldung.javapoet.test.person;
+
+import java.lang.Override;
+import java.lang.String;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.IntStream;
+
+public class Student implements Person {
+    private String name;
+
+    @Override
+    public String getName() {
+        return this.name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public void printNameMultipleTimes() {
+        List<String> names = new ArrayList<>();
+        IntStream.range(0, 10).forEach(i -> names.add(name));
+        names.forEach(System.out::println);
+    }
+
+    public static void sortByLength(List<String> strings) {
+        Collections.sort(strings, new Comparator<String>() {
+            @Override
+            public int compare(String a, String b) {
+                return a.length() - b.length();
+            }
+        });
+    }
+}