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点评：一篇很有实操意义的文档

之前写了JAVA操作cassandra驱动包，现在来看看spring-data对cassandra的支持。这里是spring-data-cassandra的官方文档：

这个目录下还有api、版本日志等：

引入jar包

   
      
    
     org.springframework.data
        
    
     spring-data-cassandra
        
    
     1.5.0.M1
    
   

定义域模型（实体类）

不存在复合主键的情况：

package com.my.domin.pojo;import org.springframework.data.cassandra.mapping.Column;import org.springframework.data.cassandra.mapping.PrimaryKey;import org.springframework.data.cassandra.mapping.Table;@Tablepublic class Person{
       // 主键    @PrimaryKey    private String id;    // 列名 与数据库列名一致时可不加    @Column(value = "name")    private String name;    private int age;    // 支持构造函数    public Person(String id, String name, int age)    {
           this.id = id;        this.name = name;        this.age = age;    }    public String getId()    {
           return id;    }    public void setId(String id)    {
           this.id = id;    }    public String getName()    {
           return name;    }    public void setName(String name)    {
           this.name = name;    }    public int getAge()    {
           return age;    }    public void setAge(int age)    {
           this.age = age;    }    @Override    public String toString()    {
           return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";    }}

对应的CQL建表语句

CREATE TABLE mydb.person (    id text PRIMARY KEY,    age int,    name text)

可以看出和JPA的注解很类似，不同的是cassandra主键用的是@PrimaryKey，而且允许使用构造函数。

如果存在复合主键，则要先映射一个主键的实体类，再映射一个包含这个主键的实体类

package com.my.domin.pojo;import org.springframework.cassandra.core.Ordering;import org.springframework.cassandra.core.PrimaryKeyType;import org.springframework.data.cassandra.mapping.PrimaryKeyClass;import org.springframework.data.cassandra.mapping.PrimaryKeyColumn;@PrimaryKeyClasspublic class Person2Key{
       // 分区键    @PrimaryKeyColumn(name = "id", ordinal = 0, type = PrimaryKeyType.PARTITIONED)    private String id;    // 集群键    @PrimaryKeyColumn(name = "name", ordinal = 1, type = PrimaryKeyType.CLUSTERED, ordering = Ordering.DESCENDING)    private String name;    public String getId()    {
           return id;    }    public void setId(String id)    {
           this.id = id;    }    public String getName()    {
           return name;    }    public void setName(String name)    {
           this.name = name;    }    @Override    public String toString()    {
           return "Person2Key [id=" + id + ", name=" + name + "]";    }}

package com.my.domin.pojo;import org.springframework.data.cassandra.mapping.PrimaryKey;import org.springframework.data.cassandra.mapping.Table;@Table(value = "person2")public class Person2{
       @PrimaryKey    private Person2Key pKey;    private int age;    public Person2Key getpKey()    {
           return pKey;    }    public void setpKey(Person2Key pKey)    {
           this.pKey = pKey;    }    public int getAge()    {
           return age;    }    public void setAge(int age)    {
           this.age = age;    }    @Override    public String toString()    {
           return "Person2 [pKey=" + pKey + ", age=" + age + "]";    }}

对应的CQL建表语句

CREATE TABLE mydb.person2 (    id text,    name text,    age int,    PRIMARY KEY (id, name)) WITH CLUSTERING ORDER BY (name DESC)

其中的WITH CLUSTERING ORDER BY (name DESC) 对应主键类里的ordering = Ordering.DESCENDING，按照name降序存储，只有集群键才能在建表时设置降序存储。

其实还有更加复杂的复合分区键、复合集群键组合成的主键，看懂了上面应该就能举一反三了，而且用的不多，这里就不写了。

定义spring-data接口

package com.my.repository;import java.util.List;import org.springframework.data.cassandra.repository.Query;import org.springframework.data.repository.CrudRepository;import org.springframework.stereotype.Repository;import com.my.domin.pojo.Person2;@Repositorypublic interface PersonRepository extends CrudRepository
   
    {
       @Query("select * from Person2 where id= ?1 and name= ?2")    List
    
      findByIdAndName(String id, String name);}
    
   

我们可以看看继承的CrudRepository这个仓库接口类

/* * Copyright 2008-2011 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.springframework.data.repository;import java.io.Serializable;/** * Interface for generic CRUD operations on a repository for a specific type. *  * @author Oliver Gierke * @author Eberhard Wolff */@NoRepositoryBeanpublic interface CrudRepository
   
     extends Repository
    
      {
       /**     * Saves a given entity. Use the returned instance for further operations as the save operation might have changed the     * entity instance completely.     *      * @param entity     * @return the saved entity     */    
      S save(S entity);    /**     * Saves all given entities.     *      * @param entities     * @return the saved entities     * @throws IllegalArgumentException in case the given entity is {@literal null}.     */     Iterable save(Iterable entities); /** * Retrieves an entity by its id. * * @param id must not be {@literal null}. * @return the entity with the given id or {@literal null} if none found * @throws IllegalArgumentException if {@code id} is {@literal null} */ T findOne(ID id); /** * Returns whether an entity with the given id exists. * * @param id must not be {@literal null}. * @return true if an entity with the given id exists, {@literal false} otherwise * @throws IllegalArgumentException if {@code id} is {@literal null} */ boolean exists(ID id); /** * Returns all instances of the type. * * @return all entities */ Iterable
         
           findAll(); /** * Returns all instances of the type with the given IDs. * * @param ids * @return */ Iterable
          
            findAll(Iterable
           
             ids); /** * Returns the number of entities available. * * @return the number of entities */ long count(); /** * Deletes the entity with the given id. * * @param id must not be {@literal null}. * @throws IllegalArgumentException in case the given {@code id} is {@literal null} */ void delete(ID id); /** * Deletes a given entity. * * @param entity * @throws IllegalArgumentException in case the given entity is {@literal null}. */ void delete(T entity); /** * Deletes the given entities. * * @param entities * @throws IllegalArgumentException in case the given {@link Iterable} is {@literal null}. */ void delete(Iterable
             entities); /** * Deletes all entities managed by the repository. */ void deleteAll();}
           
          
         
    
   

这里面实现了一组CURD方法，如果要写一些条件查询的话可以参考

@Query("select * from Person where id= ?1 and name= ?2 ALLOW FILTERING") List
   
     findByIdAndName(String id, String name);
   

这里要注意的是cassandra支持的查询是有限制的，可以参考这篇文章http://zhaoyanblog.com/archives/265.html 。3.0之后的版本改善了许多（如上面的查询3.0以下的版本是不支持的，name为非主键字段），一个是支持了非主键的条件查询，一个是降低了集群键的查询限制条件，这里最好自己在cql中测试一下。

spring-data-cassandra文档里还提到一个分页的仓库接口类PagingAndSortingRepository，这个继承自CrudRepository，而且提供了2个分页方法。但是经过测试是不能用的。。至少我没有测试通过，不知道是没有实现（比较倾向于这个，cassandra分页的确比较麻烦），还是自己没有正确使用。

application.xml配置文件

看名字就知道spring-data-cassandra是和spring一起使用的，下面的配置只是最最基本的，更多的配置选项可以参考 这篇文章。

这个配置文件都有注释，没什么可讲的，唯一要注意的是<cassandra:template id=“cqlTemplate” /> ，官方文档上写的是<cassandra:template id=“cassandraTemplate” />，经过测试官方文档上写的不能使用，改为上面的就好了。

其中cassandra.properties文件配置

#cassandra数据库连接#节点ipcassandra_contactpoints=192.168.3.89#端口cassandra_port=9042#当前操作键空间cassandra_keyspace=mydb#登录用户名cassandra_username=cassandra#登录密码cassandra_password=cassandra

使用测试

cassandra数据库person表中数据如下： 测试方法：

package com.my.serviceImpl;import java.util.Iterator;import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.cassandra.core.CassandraOperations;import org.springframework.stereotype.Service;import com.datastax.driver.core.querybuilder.QueryBuilder;import com.datastax.driver.core.querybuilder.Select;import com.my.domin.pojo.Person;import com.my.repository.PersonRepository;import com.my.service.PersonService;@Servicepublic class PersonServiceImpl implements PersonService{
       @Autowired    private PersonRepository personRepository;    @Autowired    private CassandraOperations cassandraOperations;    @Override    public void test()    {
           //通过Repository查询        Iterable
   
     iterable = personRepository.findAll();        Iterator
    
      it = iterable.iterator();        System.out.println("==>findAll:");        while (it.hasNext())        {
               Person p = it.next();            System.out.println(p.toString());        }                //通过Repository 自定义查询查询        List
     
       list = personRepository.findByIdAndName("1", "one");        System.out.println("==>findByIdAndName:");        for (Person person : list)        {
               System.out.println(person.toString());        }        //通过cassandraOperations查询        Select select = QueryBuilder.select().from("person");        select.where(QueryBuilder.eq("id", "1"));        Person person = cassandraOperations.selectOne(select, Person.class);        System.out.println("==>cassandraOperations:");        System.out.println(person.toString());    }}
     
    
   

打印结果

这里面包含2种使用方法，一个是使用自己定义的仓库接口类，另一个是spring-data-cassandra提供的CassandraOperations类。CassandraOperations使用方式很多，上面只是列举了一种，其他具体应用官方文档都有说明。

到这里就告一段落了，官方文档还有很多内容，等有时间再去慢慢看了。

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