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https://issues.apache.org/jira/browse/LOG4J2-2118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16252176#comment-16252176
]
ASF GitHub Bot commented on LOG4J2-2118:
----------------------------------------
Github user zslayton commented on a diff in the pull request:
https://github.com/apache/logging-log4j2/pull/131#discussion_r150963138
--- Diff:
log4j-core/src/main/java/org/apache/logging/log4j/core/impl/MutableLogEvent.java
---
@@ -295,7 +301,7 @@ public Message memento() {
return message;
}
final Object[] params = parameters == null ? new Object[0] :
Arrays.copyOf(parameters, parameterCount);
- return new ParameterizedMessage(messageText.toString(), params);
+ return new ParameterizedMessage(getFormat(), params);
--- End diff --
The original version of this code appears to cause nested pattern
interpretation. For example, if you created a message with the pattern `"{}"`
and the first parameter was `"json: [{}]"`, calling `memento()` on this event
would cause the fully formatted message (`json: [{}]`) to be treated as the
format for the `ParameterizedMessage` being constructed here. Because it
contains braces, the message would attempt to pull from the parameter list to
format it.
> MutableLogEvent does not retain the Message format string
> ---------------------------------------------------------
>
> Key: LOG4J2-2118
> URL: https://issues.apache.org/jira/browse/LOG4J2-2118
> Project: Log4j 2
> Issue Type: Bug
> Components: Layouts
> Affects Versions: 2.8
> Environment: Mac OS X 10.11.6
> Java 1.8.0_141
> Reporter: Zack Slayton
> Labels: layout
>
> I'm attempting to create a custom binary Layout that stores the provided
> format string separate from the parameters rather than eagerly formatting
> them all into a single piece of text. However, when I went to implement
> `Layout::toByteArray`, I discovered that the `Message::getFormat` method
> always returns null.
> {code:java}
> import org.apache.logging.log4j.LogManager;
> import org.apache.logging.log4j.Logger;
> import org.apache.logging.log4j.core.LogEvent;
> import org.apache.logging.log4j.core.config.plugins.Plugin;
> import org.apache.logging.log4j.core.config.plugins.PluginFactory;
> import org.apache.logging.log4j.core.layout.AbstractLayout;
> import java.io.Serializable;
> import java.util.Arrays;
> @Plugin(name = "MyLayout", category = "Core", elementType = "layout",
> printObject = true)
> public class MyLayout extends AbstractLayout {
> public MyLayout() {
> super(null, null, null);
> }
> @PluginFactory
> public static MyLayout createLayout(){
> return new MyLayout();
> }
> public static void main(String[] args) {
> Logger log = LogManager.getLogger(MyLayout.class);
> log.info("Here's a thing: {}. And another: {}", 75, "walrus");
> }
> @Override
> public byte[] toByteArray(LogEvent event) {
> System.out.println("Format: " + event.getMessage().getFormat());
> System.out.println("Parameters: " +
> Arrays.toString(event.getMessage().getParameters()));
> return new byte[0];
> }
> @Override
> public Serializable toSerializable(LogEvent event) {
> return null;
> }
> @Override
> public String getContentType() {
> return null;
> }
> @Override
> public byte[] getFooter() {
> return new byte[0];
> }
> @Override
> public byte[] getHeader() {
> return new byte[0];
> }
> }
> {code}
> If I run `main` (with an extra `PatternLayout`+`Console` appender in my
> config), I see the following output:
> {code}
> 17:55:28.524 [main] INFO com.example.logging.plugins.MyLayout - Here's a
> thing: 75. And another: walrus
> Format: null
> Parameters: [75, walrus]
> {code}
> I had expected to be able to see the format string and the array of
> parameters, but instead I can only see the parameters. The format string is
> always null.
> This appears to be due to the implementation of `MutableLogEvent::setMessage`
> highlighted [in
> LOG4J2-1510|https://issues.apache.org/jira/browse/LOG4J2-1510]. Because the
> messages are reusable, they appear to be eagerly formatted and the format
> string itself is discarded. The `getFormat` method is hardcoded to return
> `null`.
> Is this by design? If so, what is the prescribed approach to getting the
> format string in my layout? (Preferably one that does not disable the
> performance optimizations offered by enabling threadlocals.)
> Thanks!
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