使用Java讀取 「Python寫入redis」 的數據踩坑記錄
-
前置環境聲明：
java8 + spring-boot-2.0.0.RELEASE + spring-boot-starter-data-redis（boot集成）java
python 3.7 64位python
redis版本4.0.1redis
在這個python腳本中寫入redis的數據是3個Student對象spring
代碼以下json
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第一部分：python寫入
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讀取：
@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屬性爲null,請檢查是否注入了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，這樣是錯誤的！ 數組
然而，這樣是錯誤的！ app
然而，這樣是錯誤的！ dom
報錯信息：ide
*************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
這是爲何呢？ spring-boot
我打開redis控制檯看一下 :
發現寫入進去的是這樣的
看似沒錯，可是爲何使用java讀取就報錯了呢 ？
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第三部分：排查問題
這時候 排查問題的思路是：咱們來使用java寫入，而且使用java讀取， 總不會出問題了吧？
咱們修改上述主類的方法以下:
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);
}
執行結果：
*************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
這時候，再打開一下redis-cli控制檯 看下存進去的是什麼格式
發現寫進去的是這樣的：
原來這和python寫進去的格式不同啊，那麼確定是各個語言本身的序列化機制的問題了
那麼大膽猜測一下啊， 若是我使用python寫入的時候，拼湊成這種帶包名+類名的格式， 是否是就能夠正常讀取了呢？
來仔細對比一下二者的差異吧：
後者竟然是一個json數組， 那咱們在python代碼中試着拼湊一下，
我修改python代碼以下：
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))
打開控制檯檢驗一下 ，看看寫進去的是什麼樣的
結構和java寫進去的如出一轍， 完美
那接着來用java程序讀一下 ：
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);
}
輸出：
*************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
猜測成功驗證，結論： 是不一樣語言序列化機制的差別致使的讀取和寫入形成格式不兼容
- 補充備註：
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 {
/**
* 自定義統一RedisTemplate序列化機制
* @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採用String的序列化方式
template.setKeySerializer(stringRedisSerializer);
// hash的key也採用String的序列化方式
template.setHashKeySerializer(stringRedisSerializer);
// value序列化方式採用jackson
template.setValueSerializer(jackson2JsonRedisSerializer);
// hash的value序列化方式採用jackson
template.setHashValueSerializer(jackson2JsonRedisSerializer);
template.afterPropertiesSet();
return template;
}
}
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