feature: format class XNode's toString method.

fix: fix zhe test.

test: add fomate Xnode toString() method test.

fix: support 3+ level format, add 3 test case for every level.

fix: fix retract.

fix: revert.

fix: exchange the test 'expect' and 'actual'

refact: only use one StringBuilder in toString method.

fix: add comments.

Author: Dreamroute

src/main/java/org/apache/ibatis/parsing/XNode.java

@@ -316,35 +316,52 @@ public Properties getChildrenAsProperties() {
   @Override
   public String toString() {
     StringBuilder builder = new StringBuilder();
-    builder.append("<");
-    builder.append(name);
-    for (Map.Entry<Object, Object> entry : attributes.entrySet()) {
-      builder.append(" ");
-      builder.append(entry.getKey());
-      builder.append("=\"");
-      builder.append(entry.getValue());
-      builder.append("\"");
-    }
-    List<XNode> children = getChildren();
-    if (!children.isEmpty()) {
-      builder.append(">\n");
-      for (XNode node : children) {
-        builder.append(node.toString());
-      }
-      builder.append("</");
-      builder.append(name);
-      builder.append(">");
-    } else if (body != null) {
-      builder.append(">");
-      builder.append(body);
-      builder.append("</");
+	  this.toString(builder, 0);
+	  return builder.toString();
+  }
+  
+  private void toString(StringBuilder builder, int level) {
+      builder.append("<");
       builder.append(name);
-      builder.append(">");
-    } else {
-      builder.append("/>");
-    }
-    builder.append("\n");
-    return builder.toString();
+      for (Map.Entry<Object, Object> entry : attributes.entrySet()) {
+          builder.append(" ");
+          builder.append(entry.getKey());
+          builder.append("=\"");
+          builder.append(entry.getValue());
+          builder.append("\"");
+      }
+      List<XNode> children = getChildren();
+      if (!children.isEmpty()) {
+          level++;
+          builder.append(">\n");
+          for (int k = 0; k < children.size(); k++) {
+              this.applySpace(builder, level);
+              children.get(k).toString(builder, level);
+          }
+          level--;
+          this.applySpace(builder, level);
+          builder.append("</");
+          builder.append(name);
+          builder.append(">");
+      } else if (body != null) {
+          builder.append(">");
+          builder.append(body);
+          builder.append("</");
+          builder.append(name);
+          builder.append(">");
+      } else {
+          builder.append("/>");
+          this.applySpace(builder, level);
+      }
+      builder.append("\n");
+  }
+  
+  private StringBuilder applySpace(StringBuilder builder, int level) {
+      for (int i=0; i<level; i++) {
+          // append 4 space, each level retract 4 space base it's parent.
+          builder.append("    ");
+      }
+      return builder;
   }
 
   private Properties parseAttributes(Node n) {

src/test/java/org/apache/ibatis/parsing/XPathParserTest.java

@@ -17,23 +17,24 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-import javax.xml.parsers.DocumentBuilder;
-import javax.xml.parsers.DocumentBuilderFactory;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.Reader;
 
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+
 import org.apache.ibatis.builder.BuilderException;
 import org.apache.ibatis.io.Resources;
 import org.junit.jupiter.api.Test;
 import org.w3c.dom.Document;
-import org.xml.sax.*;
+import org.xml.sax.InputSource;
 
 class XPathParserTest {
   private String resource = "resources/nodelet_test.xml";
 
-  //InputStream Source
+  // InputStream Source
   @Test
   void constructorWithInputStreamValidationVariablesEntityResolver() throws Exception {
 
@@ -67,7 +68,7 @@ void constructorWithInputStream() throws IOException {
     }
   }
 
-  //Reader Source
+  // Reader Source
   @Test
   void constructorWithReaderValidationVariablesEntityResolver() throws Exception {
 
@@ -101,7 +102,7 @@ void constructorWithReader() throws IOException {
     }
   }
 
-  //Xml String Source
+  // Xml String Source
   @Test
   void constructorWithStringValidationVariablesEntityResolver() throws Exception {
     XPathParser parser = new XPathParser(getXmlString(resource), false, null, null);
@@ -126,7 +127,7 @@ void constructorWithString() throws IOException {
     testEvalMethod(parser);
   }
 
-  //Document Source
+  // Document Source
   @Test
   void constructorWithDocumentValidationVariablesEntityResolver() {
     XPathParser parser = new XPathParser(getDocument(resource), false, null, null);
@@ -161,7 +162,7 @@ private Document getDocument(String resource) {
       factory.setCoalescing(false);
       factory.setExpandEntityReferences(true);
       DocumentBuilder builder = factory.newDocumentBuilder();
-      return builder.parse(inputSource);//already closed resource in builder.parse method
+      return builder.parse(inputSource);// already closed resource in builder.parse method
     } catch (Exception e) {
       throw new BuilderException("Error creating document instance.  Cause: " + e, e);
     }
@@ -193,4 +194,49 @@ private void testEvalMethod(XPathParser parser) {
     assertEquals("employee[${id_var}]_height", node.getValueBasedIdentifier());
   }
 
-}
+  @Test
+  public void formatXNodeToString() {
+    XPathParser parser = new XPathParser("<users><user><id>100</id><name>Tom</name><age>30</age><cars><car>BMW</car><car>Audi</car><car>Benz</car></cars></user></users>");
+    String usersNodeToString = parser.evalNode("/users").toString();
+    String userNodeToString = parser.evalNode("/users/user").toString();
+    String carsNodeToString = parser.evalNode("/users/user/cars").toString();
+    
+    String usersNodeToStringExpect = 
+      "<users>\n" + 
+      "    <user>\n" + 
+      "        <id>100</id>\n" + 
+      "        <name>Tom</name>\n" + 
+      "        <age>30</age>\n" + 
+      "        <cars>\n" + 
+      "            <car>BMW</car>\n" + 
+      "            <car>Audi</car>\n" + 
+      "            <car>Benz</car>\n" + 
+      "        </cars>\n" + 
+      "    </user>\n" + 
+      "</users>\n";
+
+    String userNodeToStringExpect = 
+      "<user>\n" + 
+      "    <id>100</id>\n" + 
+      "    <name>Tom</name>\n" + 
+      "    <age>30</age>\n" + 
+      "    <cars>\n" + 
+      "        <car>BMW</car>\n" + 
+      "        <car>Audi</car>\n" + 
+      "        <car>Benz</car>\n" + 
+      "    </cars>\n" + 
+      "</user>\n";
+  
+  String carsNodeToStringExpect = 
+      "<cars>\n" + 
+      "    <car>BMW</car>\n" + 
+      "    <car>Audi</car>\n" + 
+      "    <car>Benz</car>\n" + 
+      "</cars>\n";
+
+    assertEquals(usersNodeToStringExpect, usersNodeToString);
+    assertEquals(userNodeToStringExpect, userNodeToString);
+    assertEquals(carsNodeToStringExpect, carsNodeToString);
+  }
+
+}