在solrcloud出来之前，如果通过solrj连接solrserver，需要程序自己实现一致性hash.
新版本的solr支持cloud的部署方式，可以自动实现lb和sharding的功能（通过CloudSolrServer类连接cloud），可以用下面代码做测试
需要的jar包如下：

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apache-solr-solrj.jar
apache-solr-core.jar
zookeeper.jar   
commons-logging.jar 
apache-logging-log4j.jar 
httpclient.jar  
httpcore.jar
slf4j-api.jar
slf4j-nop.jar

sample code:

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import  java.io.IOException; 
import  java.util.ArrayList; 
import  java.util.Collection; 
import  org.apache.solr.client.solrj.SolrQuery; 
import  org.apache.solr.client.solrj.SolrServer; 
import  org.apache.solr.client.solrj.SolrServerException; 
import  org.apache.solr.client.solrj.impl.CloudSolrServer; 
import  org.apache.solr.client.solrj.response.QueryResponse; 
import  org.apache.solr.common.SolrDocument; 
import  org.apache.solr.common.SolrDocumentList; 
import  org.apache.solr.common.SolrInputDocument; 
import  org.apache.commons.logging.Log;
import  org.apache.commons.logging.LogFactory;   
import  org.apache.solr.common.cloud.ClusterState;
import  org.apache.solr.common.cloud.ZkStateReader;
    
     public  class  SolrCloudTest {       
        public  static  final  Log LOG = LogFactory.getLog(SolrCloudTest. class );
         private  static  CloudSolrServer cloudSolrServer;             
         private   static  synchronized  CloudSolrServer getCloudSolrServer(  final  String zkHost) {   
                LOG.info( "connect to :"  +zkHost+ "\n"  );
             if (cloudSolrServer ==  null ) {   
                 try  {   
                     cloudSolrServer =  new  CloudSolrServer(zkHost);   
                 }  catch (Exception e) {   
                     e.printStackTrace();                   
                 }   
             }                   
             return  cloudSolrServer ;   
         }   
            
         private  void  addIndex(SolrServer solrServer) {         
             try  {
               Collection<SolrInputDocument> docs =  new  ArrayList<SolrInputDocument>();
                for  ( int  i =  0 ;i<= 200 ;i++){
                      SolrInputDocument doc =  new  SolrInputDocument();
                      String key =  "" ;
                      key = String. valueOf(i);
                      doc.addField(  "id" , key);
                      doc.addField(  "test_s" , key+ "value"  );
                      docs.add(doc);             
               }    
                 LOG.info( "docs info:"  +docs+ "\n"  );
                 System. out.println( "docs length "  + docs.size());
                 solrServer.add(docs);              
                 solrServer.commit();                   
             }  catch (SolrServerException e) {   
                 System. out.println( "Add docs Exception !!!"  );   
                 e.printStackTrace();           
             }  catch (IOException e){   
                 e.printStackTrace();   
             }  catch  (Exception e) {   
                 System. out.println( "Unknowned Exception!!!!!"  );   
                 e.printStackTrace();   
             }                         
         }                        
         public  void  search(SolrServer solrServer, String Str) {         
             SolrQuery query =  new  SolrQuery();
             query.setRows( 20 );  //默认row是10，只返回10条，如果设置query.setRows(Integer. MAX_VALUE)会报错，默认最大为2147483391
             query.setQuery(Str);   
             try  { 
                LOG.info( "query string: "  + Str);
               System. out.println( "query string: "  + Str);
                 QueryResponse response = solrServer.query(query);   
                 SolrDocumentList docs = response.getResults();
                 System. out.println(docs);
                 System. out.println(docs.size());
                 System. out.println( "doc num:"  + docs.getNumFound());   
                 System. out.println( "elapse time:"  + response.getQTime());           
                 for  (SolrDocument doc : docs) {   
                     String area = (String) doc.getFieldValue(  "test_s" );   
                     String id = (String) doc.getFieldValue(  "id" );   
                     System. out.println( "id: "  + id);   
                     System. out.println( "tt_s: "  + area);   
                     System. out.println();   
                 }   
             }  catch  (SolrServerException e) {   
                 e.printStackTrace();   
             }  catch (Exception e) {   
                 e.printStackTrace();   
             }   
         }   
            
         public  void  deleteAllIndex(SolrServer solrServer) {   
             try  {   
                 solrServer.deleteByQuery(  "*:*" );
                 solrServer.commit();   
             }  catch (SolrServerException e){   
                 e.printStackTrace();   
             }  catch (IOException e) {   
                 e.printStackTrace();   
             }  catch (Exception e) {   
                 e.printStackTrace();   
             }   
         }           
         public  static  void  main(String[] args) {     
                 final  String zkHost =  "xxxxx:8080"  ;        
                 final  String  defaultCollection =  "test"  ;   
                 final  int    zkClientTimeout =  10000 ;   
                 final  int  zkConnectTimeout =  10000 ;                     
                 CloudSolrServer cloudSolrServer = getCloudSolrServer(zkHost);                    
                 cloudSolrServer.setDefaultCollection(defaultCollection);   
                 cloudSolrServer.setZkClientTimeout(zkClientTimeout);   
                 cloudSolrServer.setZkConnectTimeout(zkConnectTimeout);
                 try {
                      cloudSolrServer.connect();
                     System. out.println( "connect solr cloud zk sucess"  );           
                 }  catch  (Exception e){   
                       LOG.error( "connect to collection "  +defaultCollection+ " error\n" );
                      System. out.println( "error message is:"  +e);
                      e.printStackTrace();
                      System. exit( 1 );
                 }
                       //ZkStateReader zkStateReader = cloudSolrServer.getZkStateReader();
                       //ClusterState cloudState  = zkStateReader.getClusterState();
                       //System.out.println(cloudState);
                      
                 SolrCloudTest solrt =  new  SolrCloudTest();
                 System. out.println( "====="  );
                 try {
                      solrt.addIndex(cloudSolrServer);
                 }  catch (Exception e){
                      e.printStackTrace();
                 }
                 solrt.search(cloudSolrServer,  "id:*" );   
                 //solrt.deleteAllIndex(cloudSolrServer);         
                 System. out.println( "hashCode"  +solrt.hashCode());  
                 cloudSolrServer.shutdown();           
         }         
     }