Feature : Allow setting custom linefeed on DefaultXmlPrettyPrinter

src/main/java/com/fasterxml/jackson/dataformat/xml/util/DefaultXmlPrettyPrinter.java

@@ -77,6 +77,27 @@ public interface Indenter
      */
     protected boolean _spacesInObjectEntries = true;
 
+    /**
+     * By default, will try to set as System.getProperty("line.separator")
+     * Can later set custom lineFeed with withCustomlineFeed method
+     * @since 2.15
+     */
+    private final static String DEFAULT_LINE_FEED;
+    static {
+        String lf = null;
+        try {
+            lf = System.getProperty("line.separator");
+        } catch (Throwable t) { } // access exception?
+
+        if (lf != null) {
+            DEFAULT_LINE_FEED = lf;
+        } else {
+            DEFAULT_LINE_FEED = "\n"; // incase system has changed property name? line.separator
+        }
+    }
+
+    protected static String _lineFeed = DEFAULT_LINE_FEED;
+
     /*
     /**********************************************************
     /* State
@@ -126,6 +147,18 @@ public void indentObjectsWith(Indenter i)
 
     public void spacesInObjectEntries(boolean b) { _spacesInObjectEntries = b; }
 
+    /**
+     * Sets custom linefeed
+     * @since 2.15
+     */
+    public DefaultXmlPrettyPrinter withCustomLineFeed(String lineFeed) {
+        // 06-Feb-2023, joohyukkim: when JacksonException extends RuntimeExceptions, throw it?
+        if (lineFeed != null) {
+            _lineFeed = lineFeed;
+        }
+        return this;
+    }
+
     /*
     /**********************************************************
     /* Instantiatable impl
@@ -443,7 +476,7 @@ public void writeLeafXsiNilElement(XMLStreamWriter2 sw,
     public void writePrologLinefeed(XMLStreamWriter2 sw) throws XMLStreamException
     {
         // 06-Dec-2015, tatu: Alternatively could try calling `writeSpace()`...
-        sw.writeRaw(Lf2SpacesIndenter.SYSTEM_LINE_SEPARATOR);
+        sw.writeRaw(_lineFeed);
     }
 
     /*
@@ -506,15 +539,6 @@ protected static class Lf2SpacesIndenter
     {
         private static final long serialVersionUID = 1L;
 
-        final static String SYSTEM_LINE_SEPARATOR;
-        static {
-            String lf = null;
-            try {
-                lf = System.getProperty("line.separator");
-            } catch (Throwable t) { } // access exception?
-            SYSTEM_LINE_SEPARATOR = (lf == null) ? "\n" : lf;
-        }
-
         final static int SPACE_COUNT = 64;
         final static char[] SPACES = new char[SPACE_COUNT];
         static {
@@ -529,7 +553,7 @@ public Lf2SpacesIndenter() { }
         @Override
         public void writeIndentation(XMLStreamWriter2 sw, int level) throws XMLStreamException
         {
-            sw.writeRaw(SYSTEM_LINE_SEPARATOR);
+            sw.writeRaw(_lineFeed);
             level += level; // 2 spaces per level
             while (level > SPACE_COUNT) { // should never happen but...
             	sw.writeRaw(SPACES, 0, SPACE_COUNT); 
@@ -541,7 +565,7 @@ public void writeIndentation(XMLStreamWriter2 sw, int level) throws XMLStreamExc
         @Override
         public void writeIndentation(JsonGenerator jg, int level) throws IOException
         {
-            jg.writeRaw(SYSTEM_LINE_SEPARATOR);
+            jg.writeRaw(_lineFeed);
             level += level; // 2 spaces per level
             while (level > SPACE_COUNT) { // should never happen but...
                 jg.writeRaw(SPACES, 0, SPACE_COUNT); 

src/test/java/com/fasterxml/jackson/dataformat/xml/ser/XmlPrettyPrinterTest.java

@@ -9,6 +9,7 @@
 import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
 import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
 import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
+import com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter;
 
 public class XmlPrettyPrinterTest extends XmlTestBase
 {
@@ -188,4 +189,76 @@ public void testMultiLevel172() throws Exception
                 +"</Company>\n",
                 xml);
     }
+
+    public void testLineFeed_withCustomLineFeed() throws Exception {
+        Company root = new Company();
+        root.employee.add(new Employee("abc"));
+
+        String xml = _xmlMapper.writer()
+            .with(new DefaultXmlPrettyPrinter().withCustomLineFeed("\n\rLF\n\r"))
+            .with(ToXmlGenerator.Feature.WRITE_XML_DECLARATION)
+            .writeValueAsString(root);
+        // unify possible apostrophes to quotes
+        xml = a2q(xml);
+
+        // with indentation, should get linefeeds in prolog/epilog too
+        assertEquals("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n\rLF\n\r"
+                + "<Company>\n\rLF\n\r"
+                + "  <e>\n\rLF\n\r"
+                + "    <employee>\n\rLF\n\r"
+                + "      <id>abc</id>\n\rLF\n\r"
+                + "      <type>FULL_TIME</type>\n\rLF\n\r"
+                + "    </employee>\n\rLF\n\r"
+                + "  </e>\n\rLF\n\r"
+                + "</Company>\n\rLF\n\r",
+            xml);
+    }
+
+    public void testLineFeed_systemDefault() throws Exception {
+        Company root = new Company();
+        root.employee.add(new Employee("abc"));
+
+        String xml = _xmlMapper.writer()
+            .with(new DefaultXmlPrettyPrinter())
+            .with(ToXmlGenerator.Feature.WRITE_XML_DECLARATION)
+            .writeValueAsString(root);
+        // unify possible apostrophes to quotes
+        xml = a2q(xml);
+
+        // with indentation, should get linefeeds in prolog/epilog too
+        assertEquals("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+                + "<Company>\n"
+                + "  <e>\n"
+                + "    <employee>\n"
+                + "      <id>abc</id>\n"
+                + "      <type>FULL_TIME</type>\n"
+                + "    </employee>\n"
+                + "  </e>\n"
+                + "</Company>\n",
+            xml);
+    }
+
+    public void testLineFeed_UseSystemDefaultLineSeperatorOnNullCustomLineFeed() throws Exception {
+        Company root = new Company();
+        root.employee.add(new Employee("abc"));
+
+        String xml = _xmlMapper.writer()
+            .with(new DefaultXmlPrettyPrinter().withCustomLineFeed(null))
+            .with(ToXmlGenerator.Feature.WRITE_XML_DECLARATION)
+            .writeValueAsString(root);
+        // unify possible apostrophes to quotes
+        xml = a2q(xml);
+
+        // with indentation, should get linefeeds in prolog/epilog too
+        assertEquals("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+                + "<Company>\n"
+                + "  <e>\n"
+                + "    <employee>\n"
+                + "      <id>abc</id>\n"
+                + "      <type>FULL_TIME</type>\n"
+                + "    </employee>\n"
+                + "  </e>\n"
+                + "</Company>\n",
+            xml);
+    }
 }