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
