Cure feature envy of DefaultPluginXmlFactory leveraging OOP

Author: Vincent Potucek

api/maven-api-core/src/main/java/org/apache/maven/api/services/xml/XmlReaderRequest.java

@@ -78,6 +78,13 @@ interface Transformer {
         String transform(String source, String fieldName);
     }
 
+    default XmlReaderRequest validateReadability() {
+        if (getInputStream() == null && getReader() == null && getPath() == null && getURL() == null) {
+            throw new IllegalArgumentException("writer, outputStream or path must be non null");
+        }
+        return this;
+    }
+
     @Nonnull
     static XmlReaderRequestBuilder builder() {
         return new XmlReaderRequestBuilder();

api/maven-api-core/src/main/java/org/apache/maven/api/services/xml/XmlWriterRequest.java

@@ -28,7 +28,7 @@
 import org.apache.maven.api.annotations.Nullable;
 
 /**
- * An XML writer request.
+ * An XML writer
  *
  * @since 4.0.0
  * @param <T> the object type to read
@@ -55,6 +55,13 @@ static <T> XmlWriterRequestBuilder<T> builder() {
         return new XmlWriterRequestBuilder<>();
     }
 
+    default XmlWriterRequest<T> validateWritable() {
+        if (getWriter() == null && getOutputStream() == null && getPath() == null) {
+            throw new IllegalArgumentException("writer, outputStream or path must be non null");
+        }
+        return this;
+    }
+
     class XmlWriterRequestBuilder<T> {
         Path path;
         OutputStream outputStream;

impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultPluginXmlFactory.java

@@ -18,13 +18,12 @@
  */
 package org.apache.maven.impl;
 
+import javax.xml.stream.XMLStreamException;
+
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.io.Reader;
-import java.io.Writer;
-import java.net.URL;
 import java.nio.file.Files;
-import java.nio.file.Path;
 
 import org.apache.maven.api.annotations.Nonnull;
 import org.apache.maven.api.di.Named;
@@ -38,65 +37,54 @@
 import org.apache.maven.plugin.descriptor.io.PluginDescriptorStaxReader;
 import org.apache.maven.plugin.descriptor.io.PluginDescriptorStaxWriter;
 
-import static org.apache.maven.impl.ImplUtils.nonNull;
 import static org.apache.maven.impl.StaxLocation.getLocation;
 import static org.apache.maven.impl.StaxLocation.getMessage;
 
 @Named
 @Singleton
 public class DefaultPluginXmlFactory implements PluginXmlFactory {
+
+    static final PluginDescriptorStaxWriter WRITER = new PluginDescriptorStaxWriter();
+    static final PluginDescriptorStaxReader READER = new PluginDescriptorStaxReader();
+
     @Override
     public PluginDescriptor read(@Nonnull XmlReaderRequest request) throws XmlReaderException {
-        nonNull(request, "request");
-        Path path = request.getPath();
-        URL url = request.getURL();
-        Reader reader = request.getReader();
-        InputStream inputStream = request.getInputStream();
-        if (path == null && url == null && reader == null && inputStream == null) {
-            throw new IllegalArgumentException("path, url, reader or inputStream must be non null");
-        }
+        READER.setAddDefaultEntities(request.isAddDefaultEntities());
+        var req = request.validateReadability();
         try {
-            PluginDescriptorStaxReader xml = new PluginDescriptorStaxReader();
-            xml.setAddDefaultEntities(request.isAddDefaultEntities());
-            if (inputStream != null) {
-                return xml.read(inputStream, request.isStrict());
-            } else if (reader != null) {
-                return xml.read(reader, request.isStrict());
-            } else if (path != null) {
-                try (InputStream is = Files.newInputStream(path)) {
-                    return xml.read(is, request.isStrict());
-                }
-            } else {
-                try (InputStream is = url.openStream()) {
-                    return xml.read(is, request.isStrict());
+            if (req.getInputStream() != null) {
+                return READER.read(req.getInputStream(), req.isStrict());
+            } else if (req.getReader() != null) {
+                return READER.read(req.getReader(), req.isStrict());
+            } else if (req.getPath() != null) {
+                try (InputStream is = Files.newInputStream(req.getPath())) {
+                    return READER.read(is, req.isStrict());
                 }
             }
-        } catch (Exception e) {
+            try (InputStream is = req.getURL().openStream()) {
+                return READER.read(is, req.isStrict());
+            }
+        } catch (IOException | XMLStreamException e) {
             throw new XmlReaderException("Unable to read plugin: " + getMessage(e), getLocation(e), e);
         }
     }
 
     @Override
     public void write(XmlWriterRequest<PluginDescriptor> request) throws XmlWriterException {
-        nonNull(request, "request");
-        PluginDescriptor content = nonNull(request.getContent(), "content");
-        Path path = request.getPath();
-        OutputStream outputStream = request.getOutputStream();
-        Writer writer = request.getWriter();
-        if (writer == null && outputStream == null && path == null) {
-            throw new IllegalArgumentException("writer, outputStream or path must be non null");
-        }
+        var req = request.validateWritable();
         try {
-            if (writer != null) {
-                new PluginDescriptorStaxWriter().write(writer, content);
-            } else if (outputStream != null) {
-                new PluginDescriptorStaxWriter().write(outputStream, content);
-            } else {
-                try (OutputStream os = Files.newOutputStream(path)) {
-                    new PluginDescriptorStaxWriter().write(outputStream, content);
+            if (req.getWriter() != null) {
+                WRITER.write(req.getWriter(), req.getContent());
+            } else if (req.getOutputStream() != null) {
+                WRITER.write(req.getOutputStream(), req.getContent());
+            } else if (req.getPath() != null) {
+                try (OutputStream os = Files.newOutputStream(req.getPath())) {
+                    WRITER.write(os, req.getContent());
                 }
+            } else {
+                throw new IllegalArgumentException("writer, outputStream or path must be non null");
             }
-        } catch (Exception e) {
+        } catch (XmlWriterException | XMLStreamException | IOException e) {
             throw new XmlWriterException("Unable to write plugin: " + getMessage(e), getLocation(e), e);
         }
     }