pretty-print xml in java (#11899)

* pretty-print xml in java

* simplified pom.xml

pom.xml

@@ -1206,6 +1206,7 @@
                 <module>wicket</module>
                 <module>wildfly</module>
                 <module>xml</module>
+                <module>xml-2</module>
                 <module>xstream</module>
             </modules>
 

xml-2/.gitignore

@@ -0,0 +1 @@
+xml/.idea

xml-2/README.md

@@ -0,0 +1,5 @@
+## XML
+
+This module contains articles about eXtensible Markup Language (XML)
+
+### Relevant Articles:

xml-2/pom.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>xml-2</artifactId>
+    <version>0.1-SNAPSHOT</version>
+    <name>xml-2</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- xml libraries -->
+        <dependency>
+            <groupId>org.dom4j</groupId>
+            <artifactId>dom4j</artifactId>
+            <version>${dom4j.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>xml-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+        <plugins>
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+
+    <properties>
+        <dom4j.version>2.1.3</dom4j.version>
+    </properties>
+
+</project>

xml-2/src/main/java/com/baeldung/xml/prettyprint/XmlPrettyPrinter.java

@@ -0,0 +1,91 @@
+package com.baeldung.xml.prettyprint;
+
+import org.dom4j.DocumentHelper;
+import org.dom4j.io.OutputFormat;
+import org.dom4j.io.XMLWriter;
+import org.w3c.dom.Document;
+import org.xml.sax.InputSource;
+
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
+import javax.xml.transform.stream.StreamSource;
+import java.io.*;
+
+public class XmlPrettyPrinter {
+
+    public static String prettyPrintByTransformer(String xmlString, int indent, boolean ignoreDeclaration) {
+
+        try {
+            final InputSource src = new InputSource(new StringReader(xmlString));
+            final Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(src);
+
+            TransformerFactory transformerFactory = TransformerFactory.newInstance();
+            transformerFactory.setAttribute("indent-number", indent);
+            Transformer transformer = transformerFactory.newTransformer(new StreamSource(new StringReader(readPrettyPrintXslt())));
+            // Using the default transformer will create empty lines in Java9+
+//         Transformer transformer = transformerFactory.newTransformer();
+            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
+            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, ignoreDeclaration ? "yes" : "no");
+            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
+            // Alternatively, we can set indent-size on the transformer object
+            // transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", String.valueOf(indent));
+            Writer out = new StringWriter();
+            transformer.transform(new DOMSource(document), new StreamResult(out));
+            return out.toString();
+        } catch (Exception e) {
+            throw new RuntimeException("Error occurs when pretty-printing xml:\n" + xmlString, e);
+        }
+    }
+
+
+    public static String prettyPrintByDom4j(String xmlString, int indent, boolean skipDeclaration) {
+        try {
+            final OutputFormat format = OutputFormat.createPrettyPrint();
+            format.setEncoding("UTF-8");
+            format.setIndentSize(indent);
+            format.setSuppressDeclaration(skipDeclaration);
+
+            final org.dom4j.Document document = DocumentHelper.parseText(xmlString);
+            final StringWriter sw = new StringWriter();
+            final XMLWriter writer = new XMLWriter(sw, format);
+            writer.write(document);
+            return sw.toString();
+        } catch (Exception e) {
+            throw new RuntimeException("Error occurs when pretty-printing xml:\n" + xmlString, e);
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        InputStream inputStream = XmlPrettyPrinter.class.getResourceAsStream("/xml/emails.xml");
+        String xmlString = readFromInputStream(inputStream);
+        System.out.println("Pretty printing by Transformer");
+        System.out.println("=============================================");
+        System.out.println(prettyPrintByTransformer(xmlString, 2, true));
+        System.out.println("=============================================");
+        System.out.println("Pretty printing by Dom4j");
+        System.out.println("=============================================");
+        System.out.println(prettyPrintByDom4j(xmlString, 8, false));
+        System.out.println("=============================================");
+    }
+
+
+    private static String readPrettyPrintXslt() throws IOException {
+        InputStream inputStream = XmlPrettyPrinter.class.getResourceAsStream("/xml/prettyprint.xsl");
+        return readFromInputStream(inputStream);
+    }
+
+    private static String readFromInputStream(InputStream inputStream) throws IOException {
+        StringBuilder resultStringBuilder = new StringBuilder();
+        try (BufferedReader br = new BufferedReader(new InputStreamReader(inputStream))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                resultStringBuilder.append(line).append("\n");
+            }
+        }
+        return resultStringBuilder.toString();
+    }
+}

xml-2/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

xml-2/src/main/resources/xml/emails.xml

@@ -0,0 +1,4 @@
+<emails> <email> <from>Kai</from> <to>Amanda</to> <time>2018-03-05</time>
+<subject>I am flying to you</subject></email> <email>
+<from>Jerry</from> <to>Tom</to> <time>1992-08-08</time> <subject>Hey Tom, catch me if you can!</subject>
+</email> </emails>

xml-2/src/main/resources/xml/prettyprint.xsl

@@ -0,0 +1,11 @@
+<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:strip-space elements="*"/>
+    <xsl:output method="xml" encoding="UTF-8"/>
+
+    <xsl:template match="@*|node()">
+        <xsl:copy>
+            <xsl:apply-templates select="@*|node()"/>
+        </xsl:copy>
+    </xsl:template>
+
+</xsl:stylesheet>