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Log4JXmlNamespaceResolver hack
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4 files changed

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-28
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4 files changed

+97
-28
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‎src/Log4JXmlNamespaceResolver.cs

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,26 @@
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using System.Collections.Generic;
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using System.Xml;
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namespace Serilog.Formatting.Log4Net;
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internal sealed class Log4JXmlNamespaceResolver : IXmlNamespaceResolver
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{
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private const string Prefix = "log4j";
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private const string NamespaceName = "http://jakarta.apache.org/log4j/";
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public static readonly Log4JXmlNamespaceResolver Instance = new();
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/// <summary>
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/// The XML namespace used for Log4j events.
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/// </summary>
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/// <remarks>https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L137</remarks>
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public static readonly XmlQualifiedName Log4JXmlNamespace = new(Prefix, NamespaceName);
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private static readonly Dictionary<string, string> Namespaces = new() { [Prefix] = NamespaceName };
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IDictionary<string, string> IXmlNamespaceResolver.GetNamespacesInScope(XmlNamespaceScope scope) => Namespaces;
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string? IXmlNamespaceResolver.LookupNamespace(string prefix) => prefix == Prefix ? NamespaceName : null;
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string? IXmlNamespaceResolver.LookupPrefix(string namespaceName) => namespaceName == NamespaceName ? Prefix : null;
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}

‎src/Log4NetTextFormatter.cs

Lines changed: 10 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
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using System.Diagnostics.CodeAnalysis;
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using System.IO;
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using System.Linq;
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using System.Reflection;
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using System.Text.RegularExpressions;
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using System.Xml;
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using Serilog.Core;
@@ -84,7 +85,7 @@ public Log4NetTextFormatter(Action<Log4NetTextFormatterOptionsBuilder>? configur
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var optionsBuilder = new Log4NetTextFormatterOptionsBuilder();
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configureOptions?.Invoke(optionsBuilder);
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_options = optionsBuilder.Build();
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_usesLog4JCompatibility = ReferenceEquals(Log4NetTextFormatterOptionsBuilder.Log4JXmlNamespace, _options.XmlNamespace);
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_usesLog4JCompatibility = ReferenceEquals(Log4JXmlNamespaceResolver.Log4JXmlNamespace, _options.XmlNamespace);
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}
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/// <summary>
@@ -104,29 +105,17 @@ public void Format(LogEvent logEvent, TextWriter output)
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{
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throw new ArgumentNullException(nameof(output));
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}
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var xmlWriterOutput = _usesLog4JCompatibility ? new StringWriter() : output;
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using var writer = XmlWriter.Create(xmlWriterOutput, _options.XmlWriterSettings);
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WriteEvent(logEvent, writer);
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writer.Flush();
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using var writer = XmlWriter.Create(output, _options.XmlWriterSettings);
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if (_usesLog4JCompatibility)
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{
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// log4j writes the XML "manually", see https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L137-L145
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// The resulting XML is impossible to write with a standard compliant XML writer such as XmlWriter.
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// That's why we write the event in a StringWriter then massage the output to remove the xmlns:log4j attribute to match log4j output.
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// The XML fragment becomes valid when surrounded by an external entity, see https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L31-L49
117-
const string log4JNamespaceAttribute = """
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xmlns:log4j="http://jakarta.apache.org/log4j/"
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""";
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var xmlString = ((StringWriter)xmlWriterOutput).ToString();
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var i = xmlString.IndexOf(log4JNamespaceAttribute, StringComparison.Ordinal);
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#if NETSTANDARD2_0
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output.Write(xmlString.Substring(0, i));
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output.Write(xmlString.Substring(i + log4JNamespaceAttribute.Length));
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#else
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output.Write(xmlString.AsSpan(0, i));
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output.Write(xmlString.AsSpan(i + log4JNamespaceAttribute.Length));
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#endif
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var predefinedNamespaces = writer.GetType().GetField("_predefinedNamespaces", BindingFlags.Instance | BindingFlags.NonPublic);
112+
if (predefinedNamespaces != null && typeof(IXmlNamespaceResolver).IsAssignableFrom(predefinedNamespaces.FieldType))
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{
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predefinedNamespaces.SetValue(writer, Log4JXmlNamespaceResolver.Instance);
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}
129116
}
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WriteEvent(logEvent, writer);
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writer.Flush();
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output.Write(_options.XmlWriterSettings.NewLineChars);
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}
132121

‎src/Log4NetTextFormatterOptionsBuilder.cs

Lines changed: 1 addition & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -15,12 +15,6 @@ public class Log4NetTextFormatterOptionsBuilder
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/// <remarks>https://github.com/apache/logging-log4net/blob/rel/2.0.8/src/Layout/XmlLayout.cs#L49</remarks>
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private static readonly XmlQualifiedName Log4NetXmlNamespace = new("log4net", "http://logging.apache.org/log4net/schemas/log4net-events-1.2/");
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/// <summary>
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/// The XML namespace used for Log4j events.
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/// </summary>
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/// <remarks>https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L137</remarks>
22-
internal static readonly XmlQualifiedName Log4JXmlNamespace = new("log4j", "http://jakarta.apache.org/log4j/");
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/// <summary>
2519
/// Initialize a new instance of the <see cref="Log4NetTextFormatterOptionsBuilder"/> class.
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/// </summary>
@@ -170,7 +164,7 @@ public void UseLog4JCompatibility()
170164
_lineEnding = LineEnding.CarriageReturn | LineEnding.LineFeed;
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172166
// https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L137
173-
_xmlNamespace = Log4JXmlNamespace;
167+
_xmlNamespace = Log4JXmlNamespaceResolver.Log4JXmlNamespace;
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175169
// https://github.com/apache/log4j/blob/v1_2_17/src/main/java/org/apache/log4j/xml/XMLLayout.java#L147
176170
_cDataMode = CDataMode.Always;

‎tests/Log4JXmlNamespaceResolverTest.cs

Lines changed: 60 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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using System;
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using System.Collections.Generic;
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using System.Reflection;
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using System.Xml;
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using FluentAssertions;
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using Xunit;
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namespace Serilog.Formatting.Log4Net.Tests;
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public class Log4JXmlNamespaceResolverTest
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{
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private readonly IXmlNamespaceResolver _resolver;
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public Log4JXmlNamespaceResolverTest()
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{
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var log4JXmlNamespaceResolver = typeof(Log4NetTextFormatter).Assembly.GetType("Serilog.Formatting.Log4Net.Log4JXmlNamespaceResolver")
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?? throw new MissingMemberException("Serilog.Formatting.Log4Net.Log4JXmlNamespaceResolver");
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var instance = log4JXmlNamespaceResolver.GetField("Instance", BindingFlags.Public | BindingFlags.Static)
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?? throw new MissingFieldException("Serilog.Formatting.Log4Net.Log4JXmlNamespaceResolver", "Instance");
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_resolver = (IXmlNamespaceResolver)instance.GetValue(log4JXmlNamespaceResolver)!;
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}
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[Theory]
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[InlineData(XmlNamespaceScope.All)]
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[InlineData(XmlNamespaceScope.ExcludeXml)]
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[InlineData(XmlNamespaceScope.Local)]
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public void GetNamespacesInScope(XmlNamespaceScope scope)
28+
{
29+
var expected = new Dictionary<string, string> { ["log4j"] = "http://jakarta.apache.org/log4j/" };
30+
_resolver.GetNamespacesInScope(scope).Should().BeEquivalentTo(expected);
31+
}
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33+
[Fact]
34+
public void LookupLog4JNamespace()
35+
{
36+
_resolver.LookupNamespace("log4j").Should().Be("http://jakarta.apache.org/log4j/");
37+
}
38+
39+
[Fact]
40+
public void LookupLog4JPrefix()
41+
{
42+
_resolver.LookupPrefix("http://jakarta.apache.org/log4j/").Should().Be("log4j");
43+
}
44+
45+
[Theory]
46+
[InlineData("xmlns")]
47+
[InlineData("xml")]
48+
public void LookupStandardXmlNamespace(string prefix)
49+
{
50+
_resolver.LookupNamespace(prefix).Should().BeNull();
51+
}
52+
53+
[Theory]
54+
[InlineData("http://www.w3.org/2000/xmlns/")]
55+
[InlineData("http://www.w3.org/XML/1998/namespace")]
56+
public void LookupStandardXmlPrefix(string namespaceName)
57+
{
58+
_resolver.LookupPrefix(namespaceName).Should().BeNull();
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}
60+
}

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