Question

Since a few weeks, when I launch a map-reduce task on AppEngine I get an “Error — Could not parse response JSON data.” when trying to access the console. Any idea how to fix this?

Beginning of the dump:

Error for /_ah/pipeline/rpc/tree
java.lang.NoClassDefFoundError: org/json/JSONObject
    at com.google.appengine.tools.pipeline.impl.util.JsonUtils.mapToJson(JsonUtils.java:34)
    at com.google.appengine.tools.pipeline.impl.servlets.JsonGenerator.buildJsonRepresentation(JsonGenerator.java:106)
    at com.google.appengine.tools.pipeline.impl.servlets.JsonGenerator.getJson(JsonGenerator.java:48)
    at com.google.appengine.tools.pipeline.impl.servlets.JsonHandler.doGet(JsonHandler.java:44)
    at com.google.appengine.tools.pipeline.impl.servlets.PipelineServlet.doGet(PipelineServlet.java:96)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at fr.mncc.gwttoolbox.rpc.server.filters.CrawlFilter.doFilter(CrawlFilter.java:82)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.appstats.AppstatsFilter.doFilter(AppstatsFilter.java:141)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
...

Answer 1

You will need copy the JARs from the java/lib directory to your war/WEB-INF/lib directory, as of the current release this includes charts4j-1.2.jar, commons-logging-1.1.1.jar, guava-14.0-rc1.jar, and json.jar. This should resolve the class not found error.