[SOLR-13178] ClassCastExceptions in o.a.s.request.json.ObjectUtil for valid JSON inputs that are not objects

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: 7.5, 9.0
• Component/s: Server
• Labels: diffblue newdev

Environment

Running on Unix, using a git checkout close to master.

Steps to reproduce

• Build commit ea2c8ba of Solr as described in the section below.
• Build the films collection as described below.
• Start the server using the command “./bin/solr start -f -p 8983 -s /tmp/home”
• Request the URL above.

Compiling the server

git clone https://github.com/apache/lucene-solr
cd lucene-solr
git checkout ea2c8ba
ant compile
cd solr
ant server

Building the collection

We followed Exercise 2 from the quick start tutorial (http://lucene.apache.org/solr/guide/7_5/solr-tutorial.html#exercise-2) - for reference, I have attached a copy of the database.

mkdir -p /tmp/home
echo '<?xml version="1.0" encoding="UTF-8" ?><solr></solr>' > /tmp/home/solr.xml

In one terminal start a Solr instance in foreground:

./bin/solr start -f -p 8983 -s /tmp/home

In another terminal, create a collection of movies, with no shards and no replication:

bin/solr create -c films
curl -X POST -H 'Content-type:application/json' --data-binary '\{"add-field": {"name":"name", "type":"text_general", "multiValued":false, "stored":true}}' http://localhost:8983/solr/films/schema
curl -X POST -H 'Content-type:application/json' --data-binary '{"add-copy-field" : {"source":"*","dest":"_text_"}}' [http://localhost:8983/solr/films/schema]
./bin/post -c films example/films/films.json

• Assignee: Unassigned
• Reporter: Johannes Kloos
• Created: 29/Jan/19 15:11
• Updated: 08/Jun/19 14:58
• Resolved: 13/Feb/19 07:57

Description

Requesting any of the following URLs gives a 500 error due to a ClassCastException in o.a.s.r.j.ObjectUtil.mergeObjects:

• http://localhost:8983/solr/films/select?json=0
• http://localhost:8983/solr/films/select?json.facet=1&json.facet.field=x

The error response is caused by uncaught ClassCastExceptions, such as (for the first URL):

{{ java.lang.ClassCastException: java.lang.Long cannot be cast to java.util.Map}}
at org.apache.solr.request.json.ObjectUtil.mergeObjects(ObjectUtil.java:108)
at org.apache.solr.request.json.RequestUtil.mergeJSON(RequestUtil.java:269)
at org.apache.solr.request.json.RequestUtil.processParams(RequestUtil.java:180)
at org.apache.solr.util.SolrPluginUtils.setDefaults(SolrPluginUtils.java:167)
at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:196)
[...]

The culprit seems to be the o.a.s.r.j.RequestUtil.mergeJSON method, in particular the following fragment:
        Object o = ObjectBuilder.fromJSON(jsonStr);
        // zero-length strings or comments can cause this to be null (and a zero-length string can result from a json content-type w/o a body)
        if (o != null) {
          ObjectUtil.mergeObjects(json, path, o, handler);
                }

Note that o is an Object representing a JSON value, while SOLR seems to expect that o holds a JSON object. But in the examples above, the JSON value is a number (represented by  a Long object) instead - this is, in fact, valid JSON.

A possible fix could be to use the getObject method of ObjectUtil instead of blindly calling fromJSON.

This bug was found using Diffblue Microservices Testing. Find more information on this test campaign.

Issue Links

• Is contained by: SOLR-13180 ClassCastExceptions in o.a.s.s.facet.FacetModule for valid JSON inputs that are not objects
• Is contained by: SOLR-12330 JSON Facet syntax errors are responded as runtime exceptions with 500 code