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使用Java读取 “Python写入redis” 的数据踩坑记录

日期:2019-06-13点击:210
  • 前置环境声明:

java8 + spring-boot-2.0.0.RELEASE + spring-boot-starter-data-redis(boot集成)

python 3.7 64位

redis版本4.0.1

在这个python脚本中写入redis的数据是3个Student对象

代码如下

  • 第一部分:python写入

import redis import json redisOperator = redis.Redis(host='localhost', port=6379,password="666666") class Student(object): def __init__(self, name, age, sex): self.name = name self.age = age self.sex = sex student1 = Student("chenjun1", 18, "男") student2 = Student("chenjun2", 19, "男") student3 = Student("chenjun3", 20, "男") studentList = [] studentList.append(student1) studentList.append(student2) studentList.append(student3) print(json.dumps(student1.__dict__, ensure_ascii=False)) print(json.dumps(student2.__dict__, ensure_ascii=False)) print(json.dumps(student3.__dict__, ensure_ascii=False)) for u in studentList: redisOperator.hset("ThreeCodeInOne",u.name, json.dumps(u.__dict__, ensure_ascii=False))
  • 第二部分 ,java读取:

@SpringBootApplication public class Application implements ApplicationContextAware { private static ApplicationContext applicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { Application.applicationContext = applicationContext; } @SuppressWarnings("unchecked") public static <T> T getBean(String beanName) { assertApplicationContext(); return (T) applicationContext.getBean(beanName); } public static <T> T getBean(Class<T> requiredType) { assertApplicationContext(); return applicationContext.getBean(requiredType); } private static void assertApplicationContext() { if (Application.applicationContext == null) { throw new RuntimeException("applicaitonContext属性为null,请检查是否注入了SpringContext!"); } } public static void getStudents() { System.out.println("*************getStudentHash*************"); RedisTemplate<String, String> redisTemplate = getBean("redisTemplate"); redisTemplate.setValueSerializer(new GenericToStringSerializer<>(Object.class, Charset.forName("UTF-8"))); Object o = redisTemplate.opsForHash().get("ThreeCodeInOne", "chenjun1"); System.out.println(o); } public static void main(String[] args) { SpringApplication.run(Application.class, args); assertApplicationContext(); getStudents(); } }

然而,这样是错误的! 

然而,这样是错误的! 

然而,这样是错误的! 

报错信息:

*************getStudentHash************* Exception in thread "main" 2019-06-13 11:10:03.813 INFO 7064 --- [ Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@51931956: startup date [Thu Jun 13 11:10:01 CST 2019]; root of context hierarchy org.springframework.data.redis.serializer.SerializationException: Could not read JSON: Unexpected token (START_OBJECT), expected START_ARRAY: need JSON Array to contain As.WRAPPER_ARRAY type information for class java.lang.Object at [Source: (byte[])"{"name": "chenjun1", "age": 18, "sex": "男"}"; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (START_OBJECT), expected START_ARRAY: need JSON Array to contain As.WRAPPER_ARRAY type information for class java.lang.Object at [Source: (byte[])"{"name": "chenjun1", "age": 18, "sex": "男"}"; line: 1, column: 1] at org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer.deserialize(Jackson2JsonRedisSerializer.java:75) at org.springframework.data.redis.core.AbstractOperations.deserializeHashValue(AbstractOperations.java:354) at org.springframework.data.redis.core.DefaultHashOperations.get(DefaultHashOperations.java:54) at com.redisexample.Application.getStudents(Application.java:139) at com.redisexample.Application.main(Application.java:97) Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (START_OBJECT), expected START_ARRAY: need JSON Array to contain As.WRAPPER_ARRAY type information for class java.lang.Object at [Source: (byte[])"{"name": "chenjun1", "age": 18, "sex": "男"}"; line: 1, column: 1] at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59) at com.fasterxml.jackson.databind.DeserializationContext.wrongTokenException(DeserializationContext.java:1498) at com.fasterxml.jackson.databind.DeserializationContext.reportWrongTokenException(DeserializationContext.java:1273) at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._locateTypeId(AsArrayTypeDeserializer.java:137) at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:96) at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromAny(AsArrayTypeDeserializer.java:71) at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserializeWithType(UntypedObjectDeserializer.java:712) at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:68) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3117) at org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer.deserialize(Jackson2JsonRedisSerializer.java:73) ... 4 more 2019-06-13 11:10:03.815 INFO 7064 --- [ Thread-2] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown 

这是为什么呢? 

我打开redis控制台看一下 :

发现写入进去的是这样的

看似没错,但是为什么使用java读取就报错了呢 ?

  • 第三部分:排查问题

这时候 排查问题的思路是:我们来使用java写入,并且使用java读取, 总不会出问题了吧? 

我们修改上述主类的方法如下:

 public static void getStudents() { System.out.println("*************getStudentHash*************"); RedisTemplate<String, String> redisTemplate = getBean("redisTemplate"); Student student = new Student("chenjun1", "18", "男"); redisTemplate.opsForHash().put("ThreeCodeInOne", student.getName(), student); Object o = redisTemplate.opsForHash().get("ThreeCodeInOne", "chenjun1"); System.out.println(o); }

执行结果:

*************getStudentHash************* Student [name=chenjun1, age=18, sex=男] 2019-06-13 11:16:03.877 INFO 188 --- [ Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@61d47554: startup date [Thu Jun 13 11:16:01 CST 2019]; root of context hierarchy 2019-06-13 11:16:03.880 INFO 188 --- [ Thread-2] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown

这时候,再打开一下redis-cli控制台 看下存进去的是什么格式

发现写进去的是这样的:

原来这和python写进去的格式不一样啊,那么肯定是各个语言自己的序列化机制的问题了

那么大胆猜想一下啊, 如果我使用python写入的时候,拼凑成这种带包名+类名的格式, 是不是就可以正常读取了呢?

来仔细对比一下两者的差别吧:

后者居然是一个json数组, 那我们在python代码中试着拼凑一下, 

我修改python代码如下:

import redis import json redisOperator = redis.Redis(host='localhost', port=6379,password="666666") class Student(object): def __init__(self, name, age, sex): self.name = name self.age = age self.sex = sex def useJavaSerial(student): list = [] list.append("com.redisexample.domain.Student") list.append(student.__dict__) return json.dumps(list,ensure_ascii=False) student1 = Student("chenjun1", 18, "男") student2 = Student("chenjun2", 19, "男") student3 = Student("chenjun3", 20, "男") studentList = [] studentList.append(student1) studentList.append(student2) studentList.append(student3) print(json.dumps(student1.__dict__, ensure_ascii=False)) print(json.dumps(student2.__dict__, ensure_ascii=False)) print(json.dumps(student3.__dict__, ensure_ascii=False)) for u in studentList: redisOperator.hset("ThreeCodeInOne",u.name, useJavaSerial(u)) 

打开控制台检验一下 ,看看写进去的是什么样的

结构和java写进去的一模一样, 完美

那接着来用java程序读一下 :

 public static void getStudents() { System.out.println("*************getStudentHash*************"); RedisTemplate<String, String> redisTemplate = getBean("redisTemplate"); Object o = redisTemplate.opsForHash().get("ThreeCodeInOne", "chenjun1"); System.out.println(o); }

输出:

*************getStudentHash************* Student [name=chenjun1, age=18, sex=男] 2019-06-13 11:28:19.852 INFO 15932 --- [ Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@564718df: startup date [Thu Jun 13 11:28:17 CST 2019]; root of context hierarchy 2019-06-13 11:28:19.853 INFO 15932 --- [ Thread-2] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown

猜想成功验证,结论:  是不同语言序列化机制的差异导致的读取和写入造成格式不兼容

  • 补充备注:

Spring-data-redis的redis序列化配置:

package com.redisexample.redisconf; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.data.redis.connection.RedisConnectionFactory; import org.springframework.data.redis.core.RedisTemplate; import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer; import org.springframework.data.redis.serializer.StringRedisSerializer; import com.fasterxml.jackson.annotation.JsonAutoDetect; import com.fasterxml.jackson.annotation.PropertyAccessor; import com.fasterxml.jackson.databind.ObjectMapper; @Configuration public class RedisConfig { /** * 自定义统一RedisTemplate序列化机制 * @param factory * @return */ @Bean @SuppressWarnings("all") public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) { RedisTemplate<String, Object> template = new RedisTemplate<String, Object>(); template.setConnectionFactory(factory); Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class); ObjectMapper om = new ObjectMapper(); om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY); om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL); jackson2JsonRedisSerializer.setObjectMapper(om); StringRedisSerializer stringRedisSerializer = new StringRedisSerializer(); // key采用String的序列化方式 template.setKeySerializer(stringRedisSerializer); // hash的key也采用String的序列化方式 template.setHashKeySerializer(stringRedisSerializer); // value序列化方式采用jackson template.setValueSerializer(jackson2JsonRedisSerializer); // hash的value序列化方式采用jackson template.setHashValueSerializer(jackson2JsonRedisSerializer); template.afterPropertiesSet(); return template; } } 

 

原文链接:https://my.oschina.net/u/2338224/blog/3061507
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