"程序化自定义 Json 布局 Log4j2"

Question

I have Java<\/code> desktop client application that utilizes Log4j2 framework.<\/code> JSON structure is used when logging the exceptions or infos with custom parameters. I am trying to configure the Log4j2 programmatically for this reason. I am aware that the file based configuration is recommended but it seems like it'd be better to programmatically initialize the framework for my case.

Answer 1

A custom value as a key-value pair can be added as a component by calling the addComponent method of LayoutComponentBuilder . The following code snippet shows an example:

ConfigurationBuilder<BuiltConfiguration> builder = ConfigurationBuilderFactory.newConfigurationBuilder();
        AppenderComponentBuilder console =
                builder.newAppender("stdout", "Console")
                        .addAttribute("target", ConsoleAppender.Target.SYSTEM_OUT);
        LayoutComponentBuilder jsonLayout
                = builder.newLayout("JsonLayout")
                .addAttribute("complete", false)
                .addAttribute("compact", false)
                .addComponent(builder.newKeyValuePair("key1", "value1"))
                .addComponent(builder.newKeyValuePair("key2", "value2"));
        console.add(jsonLayout);
        builder.add(console);
        RootLoggerComponentBuilder rootLogger
                = builder.newRootLogger(Level.INFO);
        rootLogger.add(builder.newAppenderRef("stdout"));
        builder.add(rootLogger);
        builder.writeXmlConfiguration(System.out);
        return builder;

Here is the corresponding xml ouput:

<?xml version='1.0' encoding='UTF-8'?>
<Configuration>
    <Appenders>
        <Console name="stdout" target="SYSTEM_OUT">
            <JsonLayout complete="false" compact="false">
                <KeyValuePair key="key1" value="value1"/>
                <KeyValuePair key="key2" value="value2"/>
            </JsonLayout>
        </Console>
    </Appenders>
    <Loggers>
        <Root level="INFO">
            <AppenderRef ref="stdout"/>
        </Root>
    </Loggers>
</Configuration>

Tested with log4j 2.17.1

Answer 2

You can use the following class to subtract any of the attributes you want in the class from the log.

     import com.fanap.midhco.applicationUtil.JsonUtil;
     import com.fasterxml.jackson.core.util.MinimalPrettyPrinter;
     import com.fasterxml.jackson.databind.ObjectWriter;
     import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
     import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
     import org.apache.logging.log4j.core.Layout;
     import org.apache.logging.log4j.core.LogEvent;
     import org.apache.logging.log4j.core.config.Node;
     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.impl.Log4jLogEvent;
     import org.apache.logging.log4j.core.jackson.JsonConstants;
     import org.apache.logging.log4j.core.jackson.Log4jJsonObjectMapper;
     import org.apache.logging.log4j.core.layout.AbstractStringLayout;
     import org.apache.logging.log4j.core.util.StringBuilderWriter;
     import org.apache.logging.log4j.util.Strings;
     
     import java.io.IOException;
     import java.nio.charset.StandardCharsets;
     import java.util.HashSet;
     import java.util.Set;
     
     @Plugin(name = "MineCustLayout", category = Node.CATEGORY, elementType = Layout.ELEMENT_TYPE, printObject = true)
     public class MineCustLayout extends AbstractStringLayout {
     
         private final ObjectWriter objectWriter;
     
         @PluginFactory
         public static MineCustLayout createLayout(
                 @PluginAttribute(value = "locationInfo", defaultBoolean = false) final boolean locationInfo, @PluginAttribute(value = "eventEol", defaultBoolean = true) final boolean eventEol
         ) {
             final SimpleFilterProvider filters = new SimpleFilterProvider();
             final Set<String> except = new HashSet<>();
             if (!locationInfo) {
                 except.add(JsonConstants.ELT_SOURCE);
             }
             except.add("loggerFqcn");
             except.add("level");
             except.add("timeMillis");
             except.add("instant");
             except.add("thread");
             except.add("loggerName");
             except.add("threadId");
             except.add("threadPriority");
             except.add("contextMap");
             except.add("endOfBatch");
             except.add(JsonConstants.ELT_NANO_TIME);
             filters.addFilter(Log4jLogEvent.class.getName(), SimpleBeanPropertyFilter.serializeAllExcept(except));
             final ObjectWriter writer = new Log4jJsonObjectMapper().writer(new MinimalPrettyPrinter());
             return new MineCustLayout(writer.with(filters));
         }
     
         public MineCustLayout(ObjectWriter objectWriter) {
             super(StandardCharsets.UTF_8, null, null);
             this.objectWriter = objectWriter;
         }
     
     
         @Override
         public String toSerializable(LogEvent event) {
             final StringBuilderWriter writer = new StringBuilderWriter();
             try {
                 objectWriter.writeValue(writer, event);
     //            writer.write('\n');
                 return JsonUtil.getJsonObject(writer.toString()).get("message").toString() + '\n';
             } catch (final IOException e) {
                 LOGGER.error(e);
                 return Strings.EMPTY;
             }
         }
     }