import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
private void validateCQLVersion(int major) throws InvalidRequestException
{
    /*
     * The rules are:
     *   - If no version are set, we don't validate anything. The reason is
     *     that 1) old CQL2 client might not have called set_cql_version
     *     and 2) some client may have removed the set_cql_version for CQL3
     *     when updating to 1.2.0. A CQL3 client upgrading from pre-1.2
     *     shouldn't be in that case however since set_cql_version uses to
     *     be mandatory (for CQL3).
     *   - Otherwise, checks the major matches whatever was set.
     */
    SemanticVersion versionSet = state().getCQLVersion();
    if (versionSet == null)
        return;

    if (versionSet.major != major)
        throw new InvalidRequestException(
            "Cannot execute/prepare CQL" + major + " statement since the CQL has been set to CQL" + versionSet.major
          + "(This might mean your client hasn't been upgraded correctly to use the new CQL3 methods introduced in Cassandra 1.2+).");
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public static SemanticVersion[] getCQLSupportedVersion()
{
    SemanticVersion cql = org.apache.cassandra.cql.QueryProcessor.CQL_VERSION;
    SemanticVersion cql3 = org.apache.cassandra.cql3.QueryProcessor.CQL_VERSION;

    return new SemanticVersion[]{ cql, cql3 };
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public Message.Response execute(QueryState state)
{
    String cqlVersion = options.get(CQL_VERSION);
    if (cqlVersion == null)
        throw new ProtocolException("Missing value CQL_VERSION in STARTUP message");

    try 
    {
        if (new SemanticVersion(cqlVersion).compareTo(new SemanticVersion("2.99.0")) < 0)
            throw new ProtocolException(String.format("CQL version %s is not supported by the binary protocol (supported version are >= 3.0.0)", cqlVersion));
    }
    catch (IllegalArgumentException e)
    {
        throw new ProtocolException(e.getMessage());
    }

    if (options.containsKey(COMPRESSION))
    {
        String compression = options.get(COMPRESSION).toLowerCase();
        if (compression.equals("snappy"))
        {
            if (FrameCompressor.SnappyCompressor.instance == null)
                throw new ProtocolException("This instance does not support Snappy compression");
            connection.setCompressor(FrameCompressor.SnappyCompressor.instance);
        }
        else if (compression.equals("lz4"))
        {
            connection.setCompressor(FrameCompressor.LZ4Compressor.instance);
        }
        else
        {
            throw new ProtocolException(String.format("Unknown compression algorithm: %s", compression));
        }
    }

    if (DatabaseDescriptor.getAuthenticator().requireAuthentication())
        return new AuthenticateMessage(DatabaseDescriptor.getAuthenticator().getClass().getName());
    else
        return new ReadyMessage();
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public Message.Response execute(QueryState state)
{
    ClientState cState = state.getClientState();
    String cqlVersion = options.get(CQL_VERSION);
    if (cqlVersion == null)
        throw new ProtocolException("Missing value CQL_VERSION in STARTUP message");

    try 
    {
        cState.setCQLVersion(cqlVersion);
    }
    catch (InvalidRequestException e)
    {
        throw new ProtocolException(e.getMessage());
    }

    if (cState.getCQLVersion().compareTo(new SemanticVersion("2.99.0")) < 0)
        throw new ProtocolException(String.format("CQL version %s is not supported by the binary protocol (supported version are >= 3.0.0)", cqlVersion));

    if (options.containsKey(COMPRESSION))
    {
        String compression = options.get(COMPRESSION).toLowerCase();
        if (compression.equals("snappy"))
        {
            if (FrameCompressor.SnappyCompressor.instance == null)
                throw new ProtocolException("This instance does not support Snappy compression");
            connection.setCompressor(FrameCompressor.SnappyCompressor.instance);
        }
        else
        {
            throw new ProtocolException(String.format("Unknown compression algorithm: %s", compression));
        }
    }

    if (DatabaseDescriptor.getAuthenticator().requireAuthentication())
        return new AuthenticateMessage(DatabaseDescriptor.getAuthenticator().getClass().getName());
    else
        return new ReadyMessage();
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public SemanticVersion getCQLVersion()
{
    return cqlVersion;
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public Message.Response execute(QueryState state)
{
    ClientState cState = state.getClientState();
    String cqlVersion = options.get(CQL_VERSION);
    if (cqlVersion == null)
        throw new ProtocolException("Missing value CQL_VERSION in STARTUP message");

    try 
    {
        cState.setCQLVersion(cqlVersion);
    }
    catch (InvalidRequestException e)
    {
        throw new ProtocolException(e.getMessage());
    }

    if (cState.getCQLVersion().compareTo(new SemanticVersion("2.99.0")) < 0)
        throw new ProtocolException(String.format("CQL version %s is not supported by the binary protocol (supported version are >= 3.0.0)", cqlVersion));

    if (options.containsKey(COMPRESSION))
    {
        String compression = options.get(COMPRESSION).toLowerCase();
        if (compression.equals("snappy"))
        {
            if (FrameCompressor.SnappyCompressor.instance == null)
                throw new ProtocolException("This instance does not support Snappy compression");
            connection.setCompressor(FrameCompressor.SnappyCompressor.instance);
        }
        else if (compression.equals("lz4"))
        {
            connection.setCompressor(FrameCompressor.LZ4Compressor.instance);
        }
        else
        {
            throw new ProtocolException(String.format("Unknown compression algorithm: %s", compression));
        }
    }

    if (DatabaseDescriptor.getAuthenticator().requireAuthentication())
        return new AuthenticateMessage(DatabaseDescriptor.getAuthenticator().getClass().getName());
    else
        return new ReadyMessage();
}
 

import org.apache.cassandra.utils.SemanticVersion; //导入依赖的package包/类
public static SemanticVersion[] getCQLSupportedVersion()
{
    return new SemanticVersion[]{ QueryProcessor.CQL_VERSION };
}