Spring Redis（4）对象Hash映射

爱被打了一巴掌 2022-06-17 00:18 193阅读 0赞

# Hash mapping #

使用Redis的hash结构存储对象有以下三种方式  
1. 使用HashOperations和序列化（见上一节）  
2. 使用Redis持久化（推荐，见后续章节）  
3. 使用HashMapper和HashOperations

这里主要介绍第三种方式  
HashMapper将对象与Map

### ObjectHashMapper ###

@Repository("hashMapping")
    public class HashMapping { 
    
        @Resource(name = "redisTemplate")
        HashOperations<String, byte[], byte[]> hashOperations;
    
        HashMapper<Object, byte[], byte[]> mapper = new ObjectHashMapper();
    
        public <T> void writeHash(String key, T obj) {
    
            Map<byte[], byte[]> mappedHash = mapper.toHash(obj);
            hashOperations.putAll(key, mappedHash);
        }
    
        @SuppressWarnings("unchecked")
        public <T> T loadHash(String key) {
    
            Map<byte[], byte[]> loadedHash = hashOperations.entries(key);
            return (T) mapper.fromHash(loadedHash);
        }
    }

测试方法

@Autowired
        HashMapping hashMapping;
    
        @Test
        public void testHashMapping() {
            String key = "SerializedRedisTemplateTest:TEST:hashMapping:1";
            Student stu1 = new Student("1", 1);
            hashMapping.writeHash(key, stu1);
            Student result = hashMapping.loadHash(key);
            Assert.assertEquals(stu1,result);
        }

### Jackson2HashMapper ###

Jackson2HashMapper支持普通映射和扁平映射两种方式。  
对于类型

public class Person { String firstname; String lastname; Address address; } public class Address { String city; String country; }

普通映射结果为

<table> 
 <thead> 
  <tr> 
   <th>Hash Field</th> 
   <th>Value</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>firstname</td> 
   <td>Jon</td> 
  </tr> 
  <tr> 
   <td>lastname</td> 
   <td>Snow</td> 
  </tr> 
  <tr> 
   <td>address</td> 
   <td>{ “city” : “Castle Black”, “country” : “The North” }</td> 
  </tr> 
 </tbody> 
</table>

扁平映射结果为

<table> 
 <thead> 
  <tr> 
   <th>Hash Field</th> 
   <th>Value</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>firstname</td> 
   <td>Jon</td> 
  </tr> 
  <tr> 
   <td>lastname</td> 
   <td>Snow</td> 
  </tr> 
  <tr> 
   <td>address.city</td> 
   <td>Castle Black</td> 
  </tr> 
  <tr> 
   <td>address.country</td> 
   <td>The North</td> 
  </tr> 
 </tbody> 
</table>

> 扁平映射需要所有属性名称不含影响到JSON路径。 因此不支持在Map的key或属性名中使用点号和括号。