BAEL-1979 Added examples for SnakeYAML Library (#4802)

* BAEL-1979 Added examples for SnakeYAML Library

* BAEL-1979 Moved the snakeyaml related code to libraries module

* BAEL-1979 Removed the System.out.println() statements and converted the assertTrue to assertEquals wherever possible.

* BAEL-1979 Removed println statements, small formatting fix in pom.xml

libraries/src/test/java/com/baeldung/snakeyaml/JavaToYAMLSerializationUnitTest.java

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+package com.baeldung.snakeyaml;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.StringWriter;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.Test;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.nodes.Tag;
+
+import com.baeldung.snakeyaml.Customer;
+
+public class JavaToYAMLSerializationUnitTest {
+
+    @Test
+    public void whenDumpMap_thenGenerateCorrectYAML() {
+        Map<String, Object> data = new LinkedHashMap<String, Object>();
+        data.put("name", "Silenthand Olleander");
+        data.put("race", "Human");
+        data.put("traits", new String[] { "ONE_HAND", "ONE_EYE" });
+        Yaml yaml = new Yaml();
+        StringWriter writer = new StringWriter();
+        yaml.dump(data, writer);
+        String expectedYaml = "name: Silenthand Olleander\nrace: Human\ntraits: [ONE_HAND, ONE_EYE]\n";
+        assertEquals(expectedYaml, writer.toString());
+    }
+
+    @Test
+    public void whenDumpACustomType_thenGenerateCorrectYAML() {
+        Customer customer = new Customer();
+        customer.setAge(45);
+        customer.setFirstName("Greg");
+        customer.setLastName("McDowell");
+        Yaml yaml = new Yaml();
+        StringWriter writer = new StringWriter();
+        yaml.dump(customer, writer);        
+        String expectedYaml = "!!com.baeldung.snakeyaml.Customer {age: 45, contactDetails: null, firstName: Greg,\n  homeAddress: null, lastName: McDowell}\n";
+        assertEquals(expectedYaml, writer.toString());
+    }
+
+    @Test
+    public void whenDumpAsCustomType_thenGenerateCorrectYAML() {
+        Customer customer = new Customer();
+        customer.setAge(45);
+        customer.setFirstName("Greg");
+        customer.setLastName("McDowell");
+        Yaml yaml = new Yaml();
+        String expectedYaml = "{age: 45, contactDetails: null, firstName: Greg, homeAddress: null, lastName: McDowell}\n";
+        assertEquals(expectedYaml, yaml.dumpAs(customer, Tag.MAP, null));
+    }
+
+}

libraries/src/test/java/com/baeldung/snakeyaml/YAMLToJavaDeserialisationUnitTest.java

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+package com.baeldung.snakeyaml;
+
+import org.junit.Test;
+import org.yaml.snakeyaml.TypeDescription;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.constructor.Constructor;
+
+import java.io.InputStream;
+import java.util.Date;
+import java.util.Map;
+
+import static org.junit.Assert.*;
+
+public class YAMLToJavaDeserialisationUnitTest {
+
+    @Test
+    public void whenLoadYAMLDocument_thenLoadCorrectMap() {
+        Yaml yaml = new Yaml();
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customer.yaml");
+        Map<String, Object> obj = yaml.load(inputStream);
+        assertEquals("John", obj.get("firstName"));
+        assertEquals("Doe", obj.get("lastName"));
+        assertEquals(20, obj.get("age"));
+    }
+
+    @Test
+    public void whenLoadYAMLDocumentWithTopLevelClass_thenLoadCorrectJavaObject() {
+        Yaml yaml = new Yaml(new Constructor(Customer.class));
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customer.yaml");
+        Customer customer = yaml.load(inputStream);
+        assertEquals("John", customer.getFirstName());
+        assertEquals("Doe", customer.getLastName());
+        assertEquals(20, customer.getAge());
+    }
+
+    @Test
+    public void whenLoadYAMLDocumentWithAssumedClass_thenLoadCorrectJavaObject() {
+        Yaml yaml = new Yaml();
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customer_with_type.yaml");
+        Customer customer = yaml.load(inputStream);
+        assertEquals("John", customer.getFirstName());
+        assertEquals("Doe", customer.getLastName());
+        assertEquals(20, customer.getAge());
+    }
+
+    @Test
+    public void whenLoadYAML_thenLoadCorrectImplicitTypes() {
+        Yaml yaml = new Yaml();
+        Map<Object, Object> document = yaml.load("3.0: 2018-07-22");
+        assertNotNull(document);
+        assertEquals(1, document.size());
+        assertTrue(document.containsKey(3.0d));
+        assertTrue(document.get(3.0d) instanceof Date);
+    }
+
+    @Test
+    public void whenLoadYAMLDocumentWithTopLevelClass_thenLoadCorrectJavaObjectWithNestedObjects() {
+        Yaml yaml = new Yaml(new Constructor(Customer.class));
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customer_with_contact_details_and_address.yaml");
+        Customer customer = yaml.load(inputStream);
+        assertNotNull(customer);
+        assertEquals("John", customer.getFirstName());
+        assertEquals("Doe", customer.getLastName());
+        assertEquals(31, customer.getAge());
+        assertNotNull(customer.getContactDetails());
+        assertEquals(2, customer.getContactDetails().size());
+        assertEquals("mobile", customer.getContactDetails()
+            .get(0)
+            .getType());
+        assertEquals(123456789,customer.getContactDetails()
+            .get(0)
+            .getNumber());
+        assertEquals("landline", customer.getContactDetails()
+            .get(1)
+            .getType());
+        assertEquals(456786868, customer.getContactDetails()
+            .get(1)
+            .getNumber());
+        assertNotNull(customer.getHomeAddress());
+        assertEquals("Xyz, DEF Street", customer.getHomeAddress()
+            .getLine());
+    }
+
+    @Test
+    public void whenLoadYAMLDocumentWithTypeDescription_thenLoadCorrectJavaObjectWithCorrectGenericType() {
+        Constructor constructor = new Constructor(Customer.class);
+        TypeDescription customTypeDescription = new TypeDescription(Customer.class);
+        customTypeDescription.addPropertyParameters("contactDetails", Contact.class);
+        constructor.addTypeDescription(customTypeDescription);
+        Yaml yaml = new Yaml(constructor);
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customer_with_contact_details.yaml");
+        Customer customer = yaml.load(inputStream);
+        assertNotNull(customer);
+        assertEquals("John", customer.getFirstName());
+        assertEquals("Doe", customer.getLastName());
+        assertEquals(31, customer.getAge());
+        assertNotNull(customer.getContactDetails());
+        assertEquals(2, customer.getContactDetails().size());
+        assertEquals("mobile", customer.getContactDetails()
+            .get(0)
+            .getType());
+        assertEquals("landline", customer.getContactDetails()
+            .get(1)
+            .getType());
+    }
+
+    @Test
+    public void whenLoadMultipleYAMLDocuments_thenLoadCorrectJavaObjects() {
+        Yaml yaml = new Yaml(new Constructor(Customer.class));
+        InputStream inputStream = this.getClass()
+            .getClassLoader()
+            .getResourceAsStream("yaml/customers.yaml");
+        int count = 0;
+        for (Object object : yaml.loadAll(inputStream)) {
+            count++;
+            assertTrue(object instanceof Customer);
+        }
+        assertEquals(2, count);
+    }
+
+}

libraries/src/test/resources/yaml/customer.yaml

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+firstName: "John"
+lastName: "Doe"
+age: 20

libraries/src/test/resources/yaml/customer_with_contact_details.yaml

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+firstName: "John"
+lastName: "Doe"
+age: 31
+contactDetails:
+   - { type: "mobile", number: 123456789}
+   - { type: "landline", number: 456786868}
+   

libraries/src/test/resources/yaml/customer_with_contact_details_and_address.yaml

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+firstName: "John"
+lastName: "Doe"
+age: 31
+contactDetails:
+   - type: "mobile"
+     number: 123456789
+   - type: "landline"
+     number: 456786868
+homeAddress:
+   line: "Xyz, DEF Street"
+   city: "City Y"
+   state: "State Y"
+   zip: 345657

libraries/src/test/resources/yaml/customer_with_contact_details_and_tags.yaml

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+firstName: "John"
+lastName: "Doe"
+age: 31
+contactDetails:
+   - !contact { type: "mobile", number: 123456789}
+   - !contact { type: "landline", number: 456786868}

libraries/src/test/resources/yaml/customer_with_type.yaml

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+!!com.baeldung.snakeyaml.Customer
+firstName: "John"
+lastName: "Doe"
+age: 20

libraries/src/test/resources/yaml/customers.yaml

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+---
+firstName: "John"
+lastName: "Doe"
+age: 20
+---
+firstName: "Jack"
+lastName: "Jones"
+age: 25