BAEL-2890 (#6905)

jackson-2/src/main/java/com/baeldung/jackson/node/JsonNodeIterator.java

@@ -0,0 +1,62 @@
+package com.baeldung.jackson.node;
+
+import java.util.Iterator;
+import java.util.Map.Entry;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+public class JsonNodeIterator {
+    
+    private static final String NEW_LINE = "\n";
+    private static final String FIELD_DELIMITER = ": ";
+    private static final String ARRAY_PREFIX = "- ";
+    private static final String YAML_PREFIX = "  ";
+    
+    public String toYaml(JsonNode root) {
+        StringBuilder yaml = new StringBuilder();
+        processNode(root, yaml, 0);
+        return yaml.toString();
+    }
+
+    private void processNode(JsonNode jsonNode, StringBuilder yaml, int depth) {
+        if (jsonNode.isValueNode()) {
+            yaml.append(jsonNode.asText());
+        }
+        else if (jsonNode.isArray()) {
+            for (JsonNode arrayItem : jsonNode) {
+                appendNodeToYaml(arrayItem, yaml, depth, true);
+            }
+        }
+        else if (jsonNode.isObject()) {
+            appendNodeToYaml(jsonNode, yaml, depth, false);
+        }
+    }
+    
+    private void appendNodeToYaml(JsonNode node, StringBuilder yaml, int depth, boolean isArrayItem) {
+        Iterator<Entry<String, JsonNode>> fields = node.fields();
+        boolean isFirst = true;
+        while (fields.hasNext()) {
+            Entry<String, JsonNode> jsonField = fields.next();
+            addFieldNameToYaml(yaml, jsonField.getKey(), depth, isArrayItem && isFirst);
+            processNode(jsonField.getValue(), yaml, depth+1);
+            isFirst = false;
+        }
+        
+    }
+
+private void addFieldNameToYaml(StringBuilder yaml, String fieldName, int depth, boolean isFirstInArray) {
+    if (yaml.length()>0) {
+        yaml.append(NEW_LINE);
+        int requiredDepth = (isFirstInArray) ? depth-1 : depth;
+        for(int i = 0; i < requiredDepth; i++) {
+            yaml.append(YAML_PREFIX);
+        }
+        if (isFirstInArray) {
+            yaml.append(ARRAY_PREFIX);
+        }
+    }
+    yaml.append(fieldName);
+    yaml.append(FIELD_DELIMITER);
+}
+
+}

jackson-2/src/test/java/com/baeldung/jackson/node/ExampleStructure.java

@@ -0,0 +1,18 @@
+package com.baeldung.jackson.node;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class ExampleStructure {
+    private static ObjectMapper mapper = new ObjectMapper();
+
+    static JsonNode getExampleRoot() throws IOException {
+        InputStream exampleInput = ExampleStructure.class.getClassLoader()
+            .getResourceAsStream("node_example.json");
+        JsonNode rootNode = mapper.readTree(exampleInput);
+        return rootNode;
+    }
+}

jackson-2/src/test/java/com/baeldung/jackson/node/JsonNodeIteratorUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.jackson.node;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+public class JsonNodeIteratorUnitTest {
+
+    private JsonNodeIterator onTest = new JsonNodeIterator();
+    private static String expectedYaml = "name: \n" + 
+        "  first: Tatu\n" + 
+        "  last: Saloranta\n" + 
+        "title: Jackson founder\n" + 
+        "company: FasterXML\n" + 
+        "pets: \n" + 
+        "- type: dog\n" + 
+        "  number: 1\n" + 
+        "- type: fish\n" + 
+        "  number: 50";
+    
+@Test
+public void givenANodeTree_whenIteratingSubNodes_thenWeFindExpected() throws IOException {
+    final JsonNode rootNode = ExampleStructure.getExampleRoot();
+    
+    String yaml = onTest.toYaml(rootNode);
+    System.out.println(yaml.toString());
+
+    assertEquals(expectedYaml, yaml);
+    
+}
+
+
+}

jackson-2/src/test/java/com/baeldung/jackson/node/NodeBean.java

@@ -0,0 +1,30 @@
+package com.baeldung.jackson.node;
+
+public class NodeBean {
+    private int id;
+    private String name;
+
+    public NodeBean() {
+    }
+
+    public NodeBean(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

jackson-2/src/test/java/com/baeldung/jackson/node/NodeOperationUnitTest.java

@@ -0,0 +1,119 @@
+package com.baeldung.jackson.node;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import org.junit.Test;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+public class NodeOperationUnitTest {
+    private static ObjectMapper mapper = new ObjectMapper();
+
+    @Test
+    public void givenAnObject_whenConvertingIntoNode_thenCorrect() {
+        final NodeBean fromValue = new NodeBean(2016, "baeldung.com");
+
+        final JsonNode node = mapper.valueToTree(fromValue);
+
+        assertEquals(2016, node.get("id")
+            .intValue());
+        assertEquals("baeldung.com", node.get("name")
+            .textValue());
+    }
+
+    @Test
+    public void givenANode_whenWritingOutAsAJsonString_thenCorrect() throws IOException {
+        final String pathToTestFile = "node_to_json_test.json";
+        final char[] characterBuffer = new char[50];
+
+        final JsonNode node = mapper.createObjectNode();
+        ((ObjectNode) node).put("id", 2016);
+        ((ObjectNode) node).put("name", "baeldung.com");
+
+        try (FileWriter outputStream = new FileWriter(pathToTestFile)) {
+            mapper.writeValue(outputStream, node);
+        }
+
+        try (FileReader inputStreamForAssertion = new FileReader(pathToTestFile)) {
+            inputStreamForAssertion.read(characterBuffer);
+        }
+        final String textContentOfTestFile = new String(characterBuffer);
+
+        assertThat(textContentOfTestFile, containsString("2016"));
+        assertThat(textContentOfTestFile, containsString("baeldung.com"));
+
+        Files.delete(Paths.get(pathToTestFile));
+    }
+
+    @Test
+    public void givenANode_whenConvertingIntoAnObject_thenCorrect() throws JsonProcessingException {
+        final JsonNode node = mapper.createObjectNode();
+        ((ObjectNode) node).put("id", 2016);
+        ((ObjectNode) node).put("name", "baeldung.com");
+
+        final NodeBean toValue = mapper.treeToValue(node, NodeBean.class);
+
+        assertEquals(2016, toValue.getId());
+        assertEquals("baeldung.com", toValue.getName());
+    }
+
+    @Test
+    public void givenANode_whenAddingIntoATree_thenCorrect() throws IOException {
+        final JsonNode rootNode = ExampleStructure.getExampleRoot();
+        final ObjectNode addedNode = ((ObjectNode) rootNode).putObject("address");
+        addedNode.put("city", "Seattle")
+            .put("state", "Washington")
+            .put("country", "United States");
+
+        assertFalse(rootNode.path("address")
+            .isMissingNode());
+        assertEquals("Seattle", rootNode.path("address")
+            .path("city")
+            .textValue());
+        assertEquals("Washington", rootNode.path("address")
+            .path("state")
+            .textValue());
+        assertEquals("United States", rootNode.path("address")
+            .path("country")
+            .textValue());
+    }
+
+    @Test
+    public void givenANode_whenModifyingIt_thenCorrect() throws IOException {
+        final String newString = "{\"nick\": \"cowtowncoder\"}";
+        final JsonNode newNode = mapper.readTree(newString);
+
+        final JsonNode rootNode = ExampleStructure.getExampleRoot();
+        ((ObjectNode) rootNode).set("name", newNode);
+
+        assertFalse(rootNode.path("name")
+            .path("nick")
+            .isMissingNode());
+        assertEquals("cowtowncoder", rootNode.path("name")
+            .path("nick")
+            .textValue());
+    }
+
+    @Test
+    public void givenANode_whenRemovingFromATree_thenCorrect() throws IOException {
+        final JsonNode rootNode = ExampleStructure.getExampleRoot();
+        ((ObjectNode) rootNode).remove("company");
+
+        assertTrue(rootNode.path("company")
+            .isMissingNode());
+    }
+
+}

jackson-2/src/test/resources/node_example.json

@@ -0,0 +1,18 @@
+{
+    "name": {
+        "first": "Tatu",
+        "last": "Saloranta"
+    },
+    "title": "Jackson founder",
+    "company": "FasterXML",
+    "pets": [
+        {
+            "type": "dog",
+            "number": 1
+        },
+        {
+            "type": "fish",
+            "number": 50
+        }
+    ]
+}