Added README to document the Log4J appender.

spring-data-log4j-appender/README.md

@@ -0,0 +1,40 @@
+# MongoDB Log4J Appender
+
+This module sets up a Log4J appender that puts logging events in MongoDB. It is fully configurable
+and connects directly to the MongoDB server using the driver. It has no dependency on any Spring package.
+
+To use it, configure a host, port, and database property in your Log4J configuration:
+
+    log4j.appender.stdout=org.springframework.data.document.mongodb.log4j.MongoLog4jAppender
+    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+    log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - <%m>%n
+    log4j.appender.stdout.host = localhost
+    log4j.appender.stdout.port = 27017
+    log4j.appender.stdout.database = logs
+
+It will even support properties in your MDC (so long as they're Strings or support .toString()).
+
+The collection name is configurable as well. If you don't specify anything, it will use the Category name.
+If you want to specify a collection name, you can give it a String.format() string which will be passed the
+following parameters:
+
+    1. Calendar.YEAR
+    2. Calendar.MONTH
+    3. Calendar.DAY_OF_MONTH
+    4. Calendar.HOUR_OF_DAY
+    5. event.getLevel().toString()
+    6. event.getLogger().getName()
+
+An example log entry might look like:
+
+    {
+      "_id" : ObjectId("4d88ff0975cce9d7655bda46"),
+      "name" : "org.springframework.data.document.mongodb.log4j.AppenderTest",
+      "level" : "DEBUG",
+      "timestamp" : "1300823817891",
+      "properties" : {
+        "property" : "one"
+      },
+      "message" : "DEBUG message"
+     }
+