feat(json): Add String mapping support

Author: PerfectSlayer

components/json/json-io/src/main/java/datadog/json/buffer/JsonMapper.java

@@ -2,10 +2,29 @@
 
 import java.util.Map;
 
-/** Utility class for simple Java structure mapping into JSON strings. */
+/**
+ * Utility class for simple Java structure mapping into JSON strings.
+ */
 public final class JsonMapper {
 
-  private JsonMapper() {}
+  private JsonMapper() {
+  }
+
+  /**
+   * Converts a {@link String} to a JSON string.
+   *
+   * @param string The string to convert.
+   * @return The converted JSON string.
+   */
+  public static String toJson(String string) {
+    if (string == null || string.isEmpty()) {
+      return "";
+    }
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.value(string);
+      return writer.toString();
+    }
+  }
 
   /**
    * Converts a {@link Map} to a JSON object.

components/json/json-io/src/main/java/datadog/json/buffer/JsonWriter.java

@@ -6,6 +6,7 @@
 import java.io.Flushable;
 import java.io.IOException;
 import java.io.OutputStreamWriter;
+import java.util.Locale;
 
 /**
  * A lightweight JSON writer without dependencies. It performs minimal JSON structure check unless
@@ -271,45 +272,51 @@ private void writeStringLiteral(String str) {
       this.writer.write('"');
 
       for (int i = 0; i < str.length(); ++i) {
-        char ch = str.charAt(i);
-
-        // Based on https://keploy.io/blog/community/json-escape-and-unescape
-        switch (ch) {
-          case '"':
-            this.writer.write("\\\"");
-            break;
-
-          case '\\':
-            this.writer.write("\\\\");
-            break;
-
-          case '/':
-            this.writer.write("\\/");
-            break;
-
-          case '\b':
-            this.writer.write("\\b");
-            break;
-
-          case '\f':
-            this.writer.write("\\f");
-            break;
-
-          case '\n':
-            this.writer.write("\\n");
-            break;
-
-          case '\r':
-            this.writer.write("\\r");
-            break;
-
-          case '\t':
-            this.writer.write("\\t");
-            break;
-
-          default:
-            this.writer.write(ch);
-            break;
+        char c = str.charAt(i);
+        // Escape any char outside ASCII to their Unicode equivalent
+        if (c > 127) {
+          this.writer.write('\\');
+          this.writer.write('u');
+          String hexCharacter = Integer.toHexString(c).toUpperCase(Locale.ENGLISH);
+          if (c < 4096) {
+            this.writer.write('0');
+            if (c < 256) {
+              this.writer.write('0');
+            }
+          }
+          this.writer.append(hexCharacter);
+        } else {
+          switch (c) {
+            case '"': // Quotation mark
+            case '\\': // Reverse solidus
+            case '/': // Solidus
+              this.writer.write('\\');
+              this.writer.write(c);
+              break;
+            case '\b': // Backspace
+              this.writer.write('\\');
+              this.writer.write('b');
+              break;
+            case '\f': // Form feed
+              this.writer.write('\\');
+              this.writer.write('f');
+              break;
+            case '\n': // Line feed
+              this.writer.write('\\');
+              this.writer.write('n');
+              break;
+            case '\r': // Carriage return
+              this.writer.write('\\');
+              this.writer.write('r');
+              break;
+            case '\t': // Horizontal tab
+              this.writer.write('\\');
+              this.writer.write('t');
+              break;
+            default:
+              this.writer.write(c);
+              break;
+          }
         }
       }
 
@@ -325,14 +332,4 @@ private void writeStringRaw(String str) {
       // ignore
     }
   }
-
-  private JsonWriter writeBytesRaw(byte[] bytes) {
-    try {
-      writer.flush();
-      outputStream.write(bytes);
-    } catch (IOException e) {
-      // ignore
-    }
-    return this;
-  }
 }

components/json/json-io/src/test/groovy/datadog/json/buffer/JsonMapperTest.groovy

@@ -4,7 +4,7 @@ import spock.lang.Specification
 
 class JsonMapperTest extends Specification {
 
-  def "test map toJson: #input"() {
+  def "test mapping to JSON object: #input"() {
     when:
     String json = JsonMapper.toJson((Map) input)
 
@@ -20,7 +20,7 @@ class JsonMapperTest extends Specification {
     ['key1': 'va"lu"e1', 'ke"y2': 'value2'] | "{\"key1\":\"va\\\"lu\\\"e1\",\"ke\\\"y2\":\"value2\"}"
   }
 
-  def "test iterable toJson: #input"() {
+  def "test mapping iterable to JSON array: #input"() {
     when:
     String json = JsonMapper.toJson((Iterable) input)
 
@@ -35,4 +35,44 @@ class JsonMapperTest extends Specification {
     ['value1', 'value2']   | "[\"value1\",\"value2\"]"
     ['va"lu"e1', 'value2'] | "[\"va\\\"lu\\\"e1\",\"value2\"]"
   }
+
+  def "test mapping array to JSON array: #input"() {
+    when:
+    String json = JsonMapper.toJson((String[]) input)
+
+    then:
+    json == expected
+
+    where:
+    input                  | expected
+    []                     | "[]"
+    ['value1']             | "[\"value1\"]"
+    ['value1', 'value2']   | "[\"value1\",\"value2\"]"
+    ['va"lu"e1', 'value2'] | "[\"va\\\"lu\\\"e1\",\"value2\"]"
+  }
+
+  def "test mapping to JSON string: input"() {
+    when:
+    String escaped = JsonMapper.toJson((String) string)
+
+    then:
+    escaped == expected
+
+    where:
+    string                   | expected
+    null                     | ""
+    ""                       | ""
+    ((char) 4096).toString() | '"\\u1000"'
+    ((char) 256).toString()  | '"\\u0100"'
+    ((char) 128).toString()  | '"\\u0080"'
+    "\b"                     | '"\\b"'
+    "\t"                     | '"\\t"'
+    "\n"                     | '"\\n"'
+    "\f"                     | '"\\f"'
+    "\r"                     | '"\\r"'
+    '"'                      | '"\\\""'
+    '/'                      | '"\\/"'
+    '\\'                     | '"\\\\"'
+    "a"                      | '"a"'
+  }
 }