Compare the yaml file you created with the default one, something is different. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton

On 3/04/2013, at 12:17 AM, Heinrich Götzger <goetzger@web.de> wrote:

Hello,

I try to read, edit, write and re-read a cassandra-yaml-config file programmatically, but this unfortunately does not work as expected:

Here is my example:

/* start */
package com.fue;

import java.io.*;

import org.apache.cassandra.config.*;
import org.apache.cassandra.utils.SkipNullRepresenter;
import org.yaml.snakeyaml.*;
import org.yaml.snakeyaml.DumperOptions.*;
import org.yaml.snakeyaml.constructor.*;
import org.yaml.snakeyaml.nodes.*;

public class YamlConfigTest {

  public static void main(String[] args) throws IOException {

     // 1. reading an existing config-file,
     InputStream input = new FileInputStream("/tmp/cassandra-1.2.3.yaml");

     Constructor constructor = new Constructor(Config.class);
     TypeDescription seedDesc = new TypeDescription(SeedProviderDef.class);
     seedDesc.putMapPropertyType("parameters", String.class, String.class);
     constructor.addTypeDescription(seedDesc);
     Yaml cassandraConfYaml = new Yaml(new Loader(constructor));

     Config conf = (Config) cassandraConfYaml.load(input);

     // 2. change the setting in the Config-object
     SeedProviderDef spd = conf.seed_provider;
     spd.parameters.put("seeds", "192.168.1.2");

     DumperOptions options = new DumperOptions();
     options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
     options.setDefaultScalarStyle(ScalarStyle.PLAIN);

     SkipNullRepresenter representer = new SkipNullRepresenter();
     representer.addClassTag(Config.class, Tag.MAP);

     Dumper dumper = new Dumper(representer, options);

     Yaml yamlWriter = new Yaml(new Loader(constructor), dumper);

     // 3. and writing it back to another file.
     String fileName = "/tmp/myCassandra.yaml";
     Writer output = new FileWriter(fileName);
     yamlWriter.dump(conf, output);

     Reader reader = new FileReader(fileName);

     Yaml myCassandraConfYaml = new Yaml(new Loader(constructor));

     // This procedure looses these two dashes and makes the configuration not
     // usable for further processing in other tasks.
     Config myConf = (Config) myCassandraConfYaml.load(reader);

  }
}
/* end */

And this is the output:

Exception in thread "main" Can't construct a java object for tag:yaml.org,2002:org.apache.cassandra.config.Config; exception=Cannot create property=seed_provider for JavaBean=org.apache.cassandra.config.Config@3c3ac93e; java.lang.NoSuchMethodException: org.apache.cassandra.config.SeedProviderDef.<init>()
in 'reader', line 1, column 1:
   authenticator: org.apache.cassan ...
   ^

at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:333)
at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182)
at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:141)
at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:127)
at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:481)
at org.yaml.snakeyaml.Yaml.load(Yaml.java:424)
at com.fue.YamlConfigTest.main(YamlConfigTest.java:53)
Caused by: org.yaml.snakeyaml.error.YAMLException: Cannot create property=seed_provider for JavaBean=org.apache.cassandra.config.Config@3c3ac93e; java.lang.NoSuchMethodException: org.apache.cassandra.config.SeedProviderDef.<init>()
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:299)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:189)
at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:331)
... 6 more
Caused by: org.yaml.snakeyaml.error.YAMLException: java.lang.NoSuchMethodException: org.apache.cassandra.config.SeedProviderDef.<init>()
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.createEmptyJavaBean(Constructor.java:219)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:189)
at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:296)
... 8 more
Caused by: java.lang.NoSuchMethodException: org.apache.cassandra.config.SeedProviderDef.<init>()
at java.lang.Class.getConstructor0(Class.java:2715)
at java.lang.Class.getDeclaredConstructor(Class.java:1987)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.createEmptyJavaBean(Constructor.java:215)
... 11 more

I'm using:
- snakeyaml-1.12
- cassandra-1.2.3

What am I doing wrong?
Is it a theme for cassandra or for yaml, is it in between or do I expect impossible things.


There is a thread about this in th SnakeYAML-group already:
https://groups.google.com/forum/?fromgroups=#!topic/snakeyaml-core/D4M0Ciy023E

Thanks for helping with some ideas.


Cheers

Heinrich