Difference between redis serialization genericjackson2jsonredisserializer and jackson2jsonredisserializer

 /** *  Instantiation  RedisTemplate  object  * @return */
    @Bean
    public RedisTemplate<String, Object> functionDomainRedisTemplate(RedisConnectionFactory factory) {
    
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
        // key  All use String  Serialization mode 
        redisTemplate.setKeySerializer(stringRedisSerializer);
        redisTemplate.setHashKeySerializer(stringRedisSerializer);
        GenericJackson2JsonRedisSerializer genericJackson2JsonRedisSerializer = new GenericJackson2JsonRedisSerializer();
// Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<>(Object.class);
        redisTemplate.setHashValueSerializer(genericJackson2JsonRedisSerializer);
        redisTemplate.setValueSerializer(genericJackson2JsonRedisSerializer);
        redisTemplate.setConnectionFactory(factory);
        return redisTemplate;
    }

GenericJackson2JsonRedisSerializer

GenericJackson2JsonRedisSerializer Serialization , The fully qualified name of the serialized object will be saved , from redis When obtaining data, it can be directly de sequenced into the specified object

General parameters are as follows ：

List<Student> students = new ArrayList<>();
Student xm = new Student(" Xiao Ming ", 12);
Student ph = new Student(" Fat tiger ", 12);
students.add(xm);
students.add(ph);

（1）VALUE Save common objects

save :

  Student xm = new Student(" Xiao Ming ", 12);
  redisTemplate.opsForValue().set(xm.getName(), xm);

Value is accompanied by entity information

take :

Student xmCache = (Student)redisTemplate.opsForValue().get(xm.getName());
// Student(name= Xiao Ming , age=12)
System.out.println(xmCache);

Conclusion ：GenericJackson2JsonRedisSerializer Serialization mode It can be stored directly VALUE As object , And from Redis Get strong conversion

（2）VALUE Save object collection

save :

redisTemplate.opsForSet().add("students-genericJackson2JsonRedisSerializer", students);
redisTemplate.opsForValue().set("students-str", students);

Values contain both fully qualified names of entity classes and collection types

–

The fully qualified name of the entity class is carried in the concrete value

take :

List<Student> studentCache = (List<Student>) redisTemplate.opsForValue().get("students-str");
Set<Object> members = redisTemplate.opsForSet().members("students-genericJackson2JsonRedisSerializer");
// [Student(name= Xiao Ming , age=12), Student(name= Fat tiger , age=12)]
System.out.println(studentCache);
// [Student(name= Fat tiger , age=12), Student(name= Xiao Ming , age=12)]
System.out.println(members);

Conclusion ：GenericJackson2JsonRedisSerializer Serialization mode It can be stored directly VALUE Set objects , And from Redis Get strong conversion

（3）VALUE save JSON character string

redisTemplate.opsForValue().set(ph.getName(), JSON.toJSONString(ph));

save ：

nothing @class Field , And jSON The string contains escape characters

take :

Object o = redisTemplate.opsForValue().get(ph.getName());
System.out.println(o);

Be careful : Because here is JSON character string , So when retrieving data , Nor can it be directly forced to Student object , We need to call the method manually , take JSON String conversion to JAVA object

redisTemplate.opsForValue().set(ph.getName(), JSON.toJSONString(ph));
Object o = redisTemplate.opsForValue().get(ph.getName());
// Student(name= Fat tiger , age=12)
System.out.println(o == null ? null : JSON.parseObject(o.toString(), Student.class));

Conclusion ：GenericJackson2JsonRedisSerializer Serialization mode It can be stored directly VALUE by JSON String form , And from Redis No forced conversion is allowed after obtaining , You need to convert the result into a string , then JSON The string is converted to the object or collection of objects you need

（4） The Conduit Pipelined Save the data

save :

List<Student> students = new ArrayList<>();
Student xm = new Student(" Xiao Ming ", 12); Student ph = new Student(" Fat tiger ", 12);
students.add(xm); students.add(ph);
redisTemplate.executePipelined((RedisCallback) conn -> {
    
    students.forEach(s -> conn.set(s.getName().getBytes(), JSON.toJSONString(s).getBytes()));
    return null;
});

The data of pipeline operation does not @class Entity class properties , The fully qualified name of the entity class is missing , Can we still get the data at this time ？

The answer is no

take :

Direct forced rotation after taking ：

Student xmCache = (Student)redisTemplate.opsForValue().get(xm.getName());
System.out.println(xmCache);

GET No forced transfer after taking

Object xmCache = redisTemplate.opsForValue().get(xm.getName());
System.out.println(xmCache);

MGET Batch acquisition

List<Object> objectList = redisTemplate.opsForValue().multiGet(students.stream().map(Student::getName).collect(Collectors.toList()));
System.out.println(objectList);
return objectList;

ERROR 16400 — [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.data.redis.serializer.SerializationException: Could not read JSON: Missing type id when trying to resolve subtype of [simple type, class java.lang.Object]: missing type id property ‘@class’
at [Source: (byte[])"{“age”:12,“name”:“ Xiao Ming ”}"; line: 1, column: 26]; nested exception is com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class java.lang.Object]: missing type id property ‘@class’
at [Source: (byte[])"{“age”:12,“name”:“ Xiao Ming ”}"; line: 1, column: 26]] with root cause

The translation means ： Can't read JSON： Try to parse [ Simple type , class java.lang.Object] Missing type when subtyped by ID： Missing type id attribute “@class”

Conclusion : Use GenericJackson2JsonRedisSerializer After serialization for pipeline operation , Entity class @class Attributes will be lost , Again from redis Getting data will not be able to deserialize successfully

Jackson2JsonRedisSerializer

General parameters are as follows :

List<Student> students = new ArrayList<>();
Student ys = new Student(" The rope ", 12);
Student mw = new Student(" Tryndamere ", 12);
students.add(ys);
students.add(mw);

（1）VALUE Save common objects

save :

redisTemplate.opsForValue().set(ys.getName(), ys);
redisTemplate.opsForValue().set(mw.getName(), mw);

take :

Student ysCache = (Student)redisTemplate.opsForValue().get(ys.getName());
System.out.println(ysCache);

Found an error ：java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.leilei.entity.Student

Breakpoint debugging ： Acquired ysCache It's actually a LinkedHashMap

Object ysCache = redisTemplate.opsForValue().get(ys.getName());
System.out.println(ysCache);

Save the object set, and the result is the same …

redisTemplate.opsForValue().set("lol", students);
Object lolCache = redisTemplate.opsForValue().get("lol");
System.out.println(lolCache);

terms of settlement ：

Jackson2JsonRedisSerializer Serialization All stored data adopt JSON String mode , Then, when taking data, it does not directly force the result , But use JSON Deserialization take JSON Deserialize string to java Object or collection

See example 2 ：VALUE save JSON character string

Conclusion ：Jackson2JsonRedisSerializer Serialization mode , Such as VALUE Store objects or collections of objects directly , The result is LinkedHashMap, Cannot be used directly JDK Forcibly convert a method to an object or a collection of objects , It needs tools to convert into entities and entity sets

（2）VALUE save JSON character string

save :

redisTemplate.opsForValue().set(ys.getName(), JSON.toJSONString(ys));
redisTemplate.opsForValue().set(mw.getName(), JSON.toJSONString(mw));

–

There are escape characters in the string

take ：

Object ysCache = redisTemplate.opsForValue().get(ys.getName());
// Student(name= The rope , age=122)
System.out.println(ysCache == null ? null : JSON.parseObject(ysCache.toString(), Student.class));
List<Object> cacheList = redisTemplate.opsForValue().multiGet(students.stream().map(Student::getName).collect(Collectors.toList()));
List<Student> studentList = cacheList.stream().filter(Objects::nonNull).map(Object::toString).map(x -> JSON.parseObject(x, Student.class)).collect(Collectors.toList());
// [Student(name= The rope , age=122), Student(name= Tryndamere , age=234)]
System.out.println(studentList);

Conclusion :Jackson2JsonRedisSerializer Serialization mode ,VALUE save JSON When the string , The value is also JSON character string , Need a JSON Tools to convert to entity classes or entity collections

（3） The Conduit Pipelined Save the data

save :

redisTemplate.executePipelined((RedisCallback<String>) conn -> {
    
    students.forEach(s -> conn.set(s.getName().getBytes(), JSON.toJSONString(s).getBytes()));
    return null;
});

–

take ：

Get the value stored in the pipeline to LinkedHashMap

Because we need to put map To java object , What I use here is to turn first JSON String mode

List<Object> cacheList = redisTemplate.opsForValue().multiGet(students.stream().map(Student::getName).collect(Collectors.toList()));
if (CollectionUtils.isEmpty(cacheList)) {
    
    return null;
}
List<Student> studentList = cacheList.stream().filter(Objects::nonNull).map(JSON::toJSONString).map(x -> JSON.parseObject(x, Student.class)).collect(Collectors.toList());
// [Student(name= The rope , age=122), Student(name= Tryndamere , age=234)]
System.out.println(studentList);

Conclusion ：Jackson2JsonRedisSerializer Serialization mode , And after using pipeline operation , The value obtained is also a linkedHashMap, Tools are needed to deserialize values into entity objects or collections of entity objects