[LANG-1543] [JSON string for maps] ToStringBuilder.reflectionToString

doesnt render nested maps correctly.

Apply a different version of the PR
https://github.com/apache/commons-lang/pull/561

Closes #561.

src/changes/changes.xml

@@ -81,6 +81,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action                   type="add" dev="ggregory">Add ObjectUtils.toString(Object, Supplier&lt;String&gt;).</action>
     <action issue="LANG-1567" type="update" dev="ggregory" due-to="Miguel Muñoz, Bruno P. Kinoshita, Gary Gregory">Fixed Javadocs for setTestRecursive() #556.</action>
     <action issue="LANG-1542" type="update" dev="ggregory" due-to=" Trần Ngọc Khoa, Gary Gregory">ToStringBuilder.reflectionToString - Wrong JSON format when object has a List of Enum.</action>
+    <action issue="LANG-1543" type="fix" dev="ggregory" due-to="Swaraj Pal, Gary Gregory">[JSON string for maps] ToStringBuilder.reflectionToString doesnt render nested maps correctly.</action>
     <action                   type="update" dev="ggregory">Make org.apache.commons.lang3.CharSequenceUtils.toCharArray(CharSequence) public.</action>
     <action                   type="add" dev="ggregory">Add org.apache.commons.lang3.StringUtils.substringAfter(String, int).</action>
     <action                   type="add" dev="ggregory">Add org.apache.commons.lang3.StringUtils.substringAfterLast(String, int).</action>

src/main/java/org/apache/commons/lang3/builder/ToStringStyle.java

@@ -19,7 +19,10 @@ package org.apache.commons.lang3.builder;
 import java.io.Serializable;
 import java.lang.reflect.Array;
 import java.util.Collection;
+import java.util.Iterator;
 import java.util.Map;
+import java.util.Objects;
+import java.util.Map.Entry;
 import java.util.WeakHashMap;
 
 import org.apache.commons.lang3.ClassUtils;
@@ -2595,6 +2598,37 @@ public abstract class ToStringStyle implements Serializable {
             appendDetail(buffer, fieldName, valueAsString);
         }
 
+        @Override
+        protected void appendDetail(final StringBuffer buffer, final String fieldName, final Map<?, ?> map) {
+            if (map != null && !map.isEmpty()) {
+                buffer.append(getContentStart());
+
+                boolean firstItem = true;
+                for (final Entry<?, ?> entry : map.entrySet()) {
+                    final String keyStr = Objects.toString(entry.getKey(), null);
+                    if (keyStr != null) {
+                        if (firstItem) {
+                            firstItem = false;
+                        } else {
+                            appendFieldEnd(buffer, keyStr);
+                        }
+                        appendFieldStart(buffer, keyStr);
+                        final Object value = entry.getValue();
+                        if (value == null) {
+                            appendNullText(buffer, keyStr);
+                        } else {
+                            appendInternal(buffer, keyStr, value, true);
+                        }
+                    }
+                }
+
+                buffer.append(getContentEnd());
+                return;
+            }
+
+            buffer.append(map);
+        }
+
         private boolean isJsonArray(final String valueAsString) {
             return valueAsString.startsWith(getArrayStart())
                     && valueAsString.endsWith(getArrayEnd());

src/test/java/org/apache/commons/lang3/builder/JsonToStringStyleTest.java

@@ -26,6 +26,8 @@ import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 
+import java.util.LinkedHashMap;
+import java.util.Map;
 import org.apache.commons.lang3.builder.ToStringStyleTest.Person;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -532,6 +534,70 @@ public class JsonToStringStyleTest {
         assertEquals("{\"Let's \\\"quote\\\" this\":\"value\"}", new ToStringBuilder(base).append("Let's \"quote\" this", "value").toString());
     }
 
+    @Test
+    public void testRootMap() {
+        final Map<String, Object> map = new LinkedHashMap<>();
+        map.put("k1", "v1");
+        map.put("k2", 2);
+
+        assertEquals("{\"map\":{\"k1\":\"v1\",\"k2\":2}}",
+                new ToStringBuilder(base).append("map", map).toString());
+    }
+
+    @Test
+    public void testObjectWithInnerMap() {
+        final Map<String, Object> map = new LinkedHashMap<>();
+        map.put("k1", "value1");
+        map.put("k2", 2);
+
+        final InnerMapObject object = new InnerMapObject(){
+            @Override
+            public String toString() {
+                return new ToStringBuilder(this).append("pid", this.pid)
+                        .append("map", this.map).toString();
+            }
+        };
+        object.pid = "dummy-text";
+        object.map = map;
+
+        assertEquals("{\"object\":{\"pid\":\"dummy-text\",\"map\":{\"k1\":\"value1\",\"k2\":2}}}",
+                new ToStringBuilder(base).append("object", object).toString());
+    }
+
+    @Test
+    public void testNestedMaps() {
+        final Map<String, Object> innerMap = new LinkedHashMap<>();
+        innerMap.put("k2.1", "v2.1");
+        innerMap.put("k2.2", "v2.2");
+        final Map<String, Object> baseMap = new LinkedHashMap<>();
+        baseMap.put("k1", "v1");
+        baseMap.put("k2", innerMap);
+
+        final InnerMapObject object = new InnerMapObject(){
+            @Override
+            public String toString() {
+                return new ToStringBuilder(this).append("pid", this.pid)
+                        .append("map", this.map).toString();
+            }
+        };
+        object.pid = "dummy-text";
+        object.map = baseMap;
+
+        assertEquals("{\"object\":{\"pid\":\"dummy-text\",\"map\":{\"k1\":\"v1\"," +
+                        "\"k2\":{\"k2.1\":\"v2.1\",\"k2.2\":\"v2.2\"}}}}",
+                new ToStringBuilder(base).append("object", object).toString());
+    }
+
+    @Test
+    public void testMapSkipNullKey() {
+        final Map<String, Object> map = new LinkedHashMap<>();
+        map.put("k1", "v1");
+        map.put(null, "v2");
+
+        assertEquals("{\"map\":{\"k1\":\"v1\"}}",
+                new ToStringBuilder(base).append("map", map).toString());
+    }
+
     /**
      * An object with nested object structures used to test {@link ToStringStyle.JsonToStringStyle}.
      *
@@ -616,4 +682,20 @@ public class JsonToStringStyleTest {
             return ToStringBuilder.reflectionToString(this);
         }
     }
+
+    /**
+     * An object with a Map field used to test {@link ToStringStyle.JsonToStringStyle}.
+     *
+     */
+    static class InnerMapObject {
+        /**
+         * Test String field.
+         */
+        String pid;
+
+        /**
+         * Test inner map field.
+         */
+        Map<String, Object> map;
+    }
 }