uk.gov.dwp.logging.log4j2.DwpJsonLayout Maven / Gradle / Ivy

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Wrapper class to sanitise log output and mitigate possible log forging

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package uk.gov.dwp.logging.log4j2;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.layout.AbstractStringLayout;
import org.apache.logging.log4j.core.util.Throwables;
import uk.gov.dwp.logging.LogEntryBuilderFactory;

import java.nio.charset.Charset;
import java.util.Optional;

@Plugin(
        name = "DwpJsonLayout", 
        category = "Core", 
        elementType = "layout", 
        printObject = true
)
public final class DwpJsonLayout extends AbstractStringLayout {

    private final LogEntryBuilderFactory logEntryBuilderFactory;
    
    
    public DwpJsonLayout(
            Charset charset,
            String appName,
            String version
    ) {
        super(charset);
        logEntryBuilderFactory = new LogEntryBuilderFactory(appName, version);
    }
    
    @Override
    public String toSerializable(LogEvent le) {
        
        LogEntryBuilderFactory.LogEntryBuilder builder = logEntryBuilderFactory.getBuilder()
                .withLevel(le.getLevel().name())
                .withMessage(le.getMessage().getFormattedMessage())
                .withNameSpace(le.getLoggerName())
                .withTimeStamp(le.getNanoTime())
                .withMeta("thread", ""+le.getThreadId());
                
        
        Optional.ofNullable(le.getThrown())
                .ifPresent(
                        thrown -> builder.withMeta(
                                "exception", 
                                String.join(
                                        "\n", 
                                        Throwables.toStringList(thrown)
                                                .toArray(new String[0])
                                )        
                        )
                );
        
        return builder.build();
    }
    
    @PluginFactory
    public static DwpJsonLayout createLayout(
            @PluginAttribute(
                    value = "charset", 
                    defaultString = "UTF-8"
            ) Charset charset,
            @PluginAttribute(
                    value = "app_name"
            ) String appName,
            @PluginAttribute(
                    value = "app_version"
            ) String version
    ) {
        return new DwpJsonLayout(charset, appName, version);
    }
    
}