[BAEL-6494] Add functionality to minify a JSON string (eugenp#14451)

* [BAEL-6494] Add functionality to minify JSON

* [BAEL-6494] Address review comment

---------

Co-authored-by: rajatgarg <[email protected]>

Author: rajat-garg

json-modules/json-2/src/main/java/com/baeldung/jsonminifier/JsonMinifier.java

@@ -0,0 +1,58 @@
+package com.baeldung.jsonminifier;
+
+import java.lang.reflect.Type;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+
+public class JsonMinifier {
+    public String removeExtraWhitespace(String json) {
+        StringBuilder result = new StringBuilder(json.length());
+        boolean inQuotes = false;
+        boolean escapeMode = false;
+
+        for (char character : json.toCharArray()) {
+            if (escapeMode) {
+                result.append(character);
+                escapeMode = false;
+            } else if (character == '"') {
+                inQuotes = !inQuotes;
+                result.append(character);
+            } else if (character == '\\') {
+                escapeMode = true;
+                result.append(character);
+            } else if (!inQuotes && character == ' ') {
+                continue;
+            } else {
+                result.append(character);
+            }
+        }
+
+        return result.toString();
+    }
+
+    public String removeExtraWhitespaceUsingJackson(String json) throws Exception {
+        ObjectMapper objectMapper = new ObjectMapper();
+        JsonNode jsonNode = objectMapper.readTree(json);
+        return objectMapper.writeValueAsString(jsonNode);
+    }
+
+    public String removeWhitespacesUsingGson(String json) {
+        Gson gson = new GsonBuilder().registerTypeAdapter(String.class, new StringSerializer()).create();
+        JsonElement jsonElement = gson.fromJson(json, JsonElement.class);
+        return gson.toJson(jsonElement);
+    }
+
+    class StringSerializer implements JsonSerializer<String> {
+        @Override
+        public JsonElement serialize(String src, Type typeOfSrc, JsonSerializationContext context) {
+            return new JsonPrimitive(src.trim());
+        }
+    }
+}

json-modules/json-2/src/test/java/com/baeldung/jsonminifier/JsonMinifierUnitTest.java

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+package com.baeldung.jsonminifier;
+
+import static org.junit.Assert.assertEquals;
+import org.junit.jupiter.api.Test;
+
+public class JsonMinifierUnitTest {
+    private JsonMinifier jsonMinifier = new JsonMinifier();
+    private String inputJson = "{      \"name\" : \"John\"  , \"address\" :   \"New       York\", \"age\" : 30   , \"phoneNumber\" : 9999999999    }";
+
+
+    @Test
+    public void givenWhiteSpaceRemoval_whenJsonContainsWhitespaces_thenWhitespaceRemoved() {
+        String expectedJson = "{\"name\":\"John\",\"address\":\"New       York\",\"age\":30,\"phoneNumber\":9999999999}";
+        String result = jsonMinifier.removeExtraWhitespace(inputJson);
+        System.out.println(result);
+        assertEquals(expectedJson, result);
+    }
+
+    @Test
+    public void givenWhiteSpaceRemovalUsingJackson_whenJsonContainsWhitespaces_thenWhitespaceRemoved() throws Exception {
+        String expectedJson = "{\"name\":\"John\",\"address\":\"New       York\",\"age\":30,\"phoneNumber\":9999999999}";
+        String result = jsonMinifier.removeExtraWhitespaceUsingJackson(inputJson);
+        System.out.println(result);
+        assertEquals(expectedJson, result);
+    }
+
+    @Test
+    public void givenWhiteSpaceRemovalUsingGson_whenJsonContainsWhitespaces_thenWhitespaceRemoved() {
+        String expectedJson = "{\"name\":\"John\",\"address\":\"New       York\",\"age\":30,\"phoneNumber\":9999999999}";
+        String result = jsonMinifier.removeWhitespacesUsingGson(inputJson);
+        System.out.println(result);
+        assertEquals(expectedJson, result);
+    }
+}