improve JSON escape, closes #6

src/main/java/org/xbib/marc/json/MarcJsonWriter.java

@@ -45,8 +45,6 @@ import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 import java.util.zip.Deflater;
 import java.util.zip.GZIPOutputStream;
 
@@ -65,14 +63,6 @@ public class MarcJsonWriter extends MarcContentHandler implements Flushable, Clo
 
     private static final int DEFAULT_BUFFER_SIZE = 65536;
 
-    private static final Pattern quotePattern = Pattern.compile("\"", Pattern.LITERAL);
-
-    private static final Pattern backslashPattern = Pattern.compile("\\\\");
-
-    private static final String ESCAPE_QUOTE = "\\\"";
-
-    private static final String ESCAPE_BACKSLASH = "\\\\";
-
     private final Lock lock;
 
     private final StringBuilder sb;
@@ -155,8 +145,41 @@ public class MarcJsonWriter extends MarcContentHandler implements Flushable, Clo
     }
 
     private static String escape(String value) {
-        String s = backslashPattern.matcher(value).replaceAll(Matcher.quoteReplacement(ESCAPE_BACKSLASH));
+        StringBuilder sb = new StringBuilder();
-        return quotePattern.matcher(s).replaceAll(Matcher.quoteReplacement(ESCAPE_QUOTE));
+        for (int i = 0; i < value.length(); i++) {
+            char c = value.charAt(i);
+            switch (c) {
+                case '"':
+                    sb.append("\\\"");
+                    break;
+                case '\\':
+                    sb.append("\\\\");
+                    break;
+                case '\b':
+                    sb.append("\\b");
+                    break;
+                case '\f':
+                    sb.append("\\f");
+                    break;
+                case '\n':
+                    sb.append("\\n");
+                    break;
+                case '\r':
+                    sb.append("\\r");
+                    break;
+                case '\t':
+                    sb.append("\\t");
+                    break;
+                default:
+                    if (c < 0x1f) {
+                        sb.append("\\u").append(String.format("%04x", (int) c));
+                    } else {
+                        sb.append(c);
+                    }
+                    break;
+            }
+        }
+        return sb.toString();
     }
 
     public MarcJsonWriter setIndex(String index, String indexType) {