Added validation reporting

src/main/java/net/fortuna/ical4j/validate/ValidationEntry.java

@@ -33,9 +33,10 @@
 
 package net.fortuna.ical4j.validate;
 
+import java.util.Comparator;
 import java.util.Objects;
 
-public class ValidationEntry {
+public class ValidationEntry implements Comparable<ValidationEntry> {
 
     public enum Severity {
         ERROR, WARNING, INFO
@@ -92,4 +93,12 @@ public boolean equals(Object o) {
     public int hashCode() {
         return Objects.hash(message, severity, context);
     }
+
+    @Override
+    public int compareTo(ValidationEntry o) {
+        return Comparator.comparing(ValidationEntry::getContext)
+                .thenComparing(ValidationEntry::getSeverity)
+                .thenComparing(ValidationEntry::getMessage)
+                .compare(this, o);
+    }
 }

src/main/java/net/fortuna/ical4j/validate/ValidationReport.java

@@ -0,0 +1,83 @@
+/*
+ *  Copyright (c) 2022, Ben Fortuna
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *   o Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *   o Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in the
+ *  documentation and/or other materials provided with the distribution.
+ *
+ *   o Neither the name of Ben Fortuna nor the names of any other contributors
+ *  may be used to endorse or promote products derived from this software
+ *  without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package net.fortuna.ical4j.validate;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Generate a report from a {@link ValidationResult}.
+ */
+public class ValidationReport {
+
+    public enum Format {
+        HTML, TEXT
+    }
+
+    private final Format format;
+
+    public ValidationReport() {
+        this(Format.HTML);
+    }
+
+    public ValidationReport(Format format) {
+        this.format = format;
+    }
+
+    public void output(ValidationResult result, OutputStream out) throws IOException {
+        output(result, new OutputStreamWriter(out, StandardCharsets.UTF_8));
+    }
+
+    public void output(ValidationResult result, Writer out) throws IOException {
+        switch (format) {
+            case HTML: outputHtml(result, out); break;
+            case TEXT: outputText(result, out); break;
+        }
+    }
+
+    private void outputHtml(ValidationResult result, Writer out) throws IOException {
+        for (ValidationEntry entry : result.getEntries()) {
+            out.write(String.format("<p>%s: %s - %s</p>\n", entry.getContext(), entry.getSeverity(), entry.getMessage()));
+        }
+    }
+
+    private void outputText(ValidationResult result, Writer out) throws IOException {
+        for (ValidationEntry entry : result.getEntries()) {
+            out.write(String.format("%s: %s - %s\n", entry.getContext(), entry.getSeverity(), entry.getMessage()));
+        }
+    }
+}

src/main/java/net/fortuna/ical4j/validate/ValidationResult.java

@@ -49,7 +49,7 @@ public ValidationResult(ValidationEntry...entries) {
     }
 
     public ValidationResult(Collection<ValidationEntry> entries) {
-        this.entries = new HashSet<>(entries);
+        this.entries = new TreeSet<>(entries);
     }
 
     public Set<ValidationEntry> getEntries() {
@@ -62,7 +62,7 @@ public boolean hasErrors() {
 
     public ValidationResult merge(ValidationResult result) {
         if (!result.getEntries().isEmpty()) {
-            Set<ValidationEntry> merged = new HashSet<>(entries);
+            Set<ValidationEntry> merged = new TreeSet<>(entries);
             merged.addAll(result.getEntries());
             return new ValidationResult(merged);
         } else {

src/test/groovy/net/fortuna/ical4j/validate/ValidationReportTest.groovy

@@ -0,0 +1,100 @@
+/*
+ *  Copyright (c) 2022, Ben Fortuna
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *   o Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *   o Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in the
+ *  documentation and/or other materials provided with the distribution.
+ *
+ *   o Neither the name of Ben Fortuna nor the names of any other contributors
+ *  may be used to endorse or promote products derived from this software
+ *  without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package net.fortuna.ical4j.validate
+
+import spock.lang.Specification
+
+import static net.fortuna.ical4j.validate.ValidationReport.Format.HTML
+import static net.fortuna.ical4j.validate.ValidationReport.Format.TEXT
+
+class ValidationReportTest extends Specification {
+
+    def 'generate empty text format report'() {
+        given: 'a validation result'
+        ValidationResult result = []
+
+        when: 'a report is generated'
+        StringWriter writer = []
+        new ValidationReport(TEXT).output(result, writer)
+
+        then: 'output matches expected'
+        writer as String == ''
+    }
+
+    def 'generate text format report'() {
+        given: 'a validation result'
+        ValidationResult result = []
+        result.entries << new ValidationEntry('Missing mandatory properties', ValidationEntry.Severity.ERROR,
+                'VCALENDAR')
+
+        when: 'a report is generated'
+        StringWriter writer = []
+        new ValidationReport(TEXT).output(result, writer)
+
+        then: 'output matches expected'
+        writer as String == 'VCALENDAR: ERROR - Missing mandatory properties\n'
+    }
+
+    def 'generate multiline text format report'() {
+        given: 'a validation result'
+        ValidationResult result = []
+        result.entries << new ValidationEntry('Missing mandatory properties', ValidationEntry.Severity.ERROR,
+                'VCALENDAR')
+        result.entries << new ValidationEntry('Invalid parameter', ValidationEntry.Severity.WARNING,
+                'DTSTART')
+
+        when: 'a report is generated'
+        StringWriter writer = []
+        new ValidationReport(TEXT).output(result, writer)
+
+        then: 'output matches expected'
+        writer as String == 'DTSTART: WARNING - Invalid parameter\nVCALENDAR: ERROR - Missing mandatory properties\n'
+    }
+
+    def 'generate multiline html format report'() {
+        given: 'a validation result'
+        ValidationResult result = []
+        result.entries << new ValidationEntry('Missing mandatory properties', ValidationEntry.Severity.ERROR,
+                'VCALENDAR')
+        result.entries << new ValidationEntry('Invalid parameter', ValidationEntry.Severity.WARNING,
+                'DTSTART')
+
+        when: 'a report is generated'
+        StringWriter writer = []
+        new ValidationReport(HTML).output(result, writer)
+
+        then: 'output matches expected'
+        writer as String == '<p>DTSTART: WARNING - Invalid parameter</p>\n<p>VCALENDAR: ERROR - Missing mandatory properties</p>\n'
+    }
+}