![]()
{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的基本简介","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" ","attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson是当前用的比较广泛的，用来序列化和反序列化 json 的 Java 的开源框架。Jackson 社 区相对比较活跃，更新速度也比较快， 从 Github 中的统计来看，Jackson 是最流行的 json 解析器之一 。 Spring MVC 的默认json解析器便是 Jackson。","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 所依赖的 jar 包较少 ，简单易用。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 解析大的 json 文件速度比较快；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 运行时占用内存比较低，性能比较好；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 有灵活的 API，可以很容易进行扩展和定制。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson 的 1.x 版本的包名是","attrs":{}},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"org.codehaus.jackson","attrs":{}}],"attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" ，当升级到 2.x 版本时，包名变为 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"com.fasterxml.jackson","attrs":{}}],"attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"，本文讨论的内容是基于最新的 Jackson 的 2.9.1 版本。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的核心模块","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-core：核心包，提供基于\"流模式\"解析的相关 API，它包括 JsonParser 和 JsonGenerator。 Jackson 内部实现正是通过高性能的流模式 API 的 JsonGenerator 和 JsonParser 来生成和解析 json。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-annotations：注解包，提供标准注解功能；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-databind：数据绑定包， 提供基于\"对象绑定\" 解析的相关 API （ ObjectMapper ） 和\"树模型\" 解析的相关 API （JsonNode）；基于\"对象绑定\" 解析的 API 和\"树模型\"解析的 API 依赖基于\"流模式\"解析的 API。","attrs":{}}]}]}],"attrs":{}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson 的基本用法","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" 若想在 Java 代码中使用 Jackson 的核心模块的 jar 包 ，需要在 pom.xml 中添加如下信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"清单 1.在 pom.xml 的 Jackson 的配置信息","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"
\n com.fasterxml.jackson.core \n jackson-databind \n 2.9.1 \n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" ","attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-databind 依赖 jackson-core 和 jackson-annotations，当添加 jackson-databind 之后， jackson-core 和 jackson-annotations 也随之添加到 Java 项目工程中。在添加相关依赖包之后，就可以使用 Jackson。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"ObjectMapper的使用示例","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson 最常用的 API 就是基于\"对象绑定\" 的 ObjectMapper。下面是一个 ObjectMapper 的使用的简单示例。","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"ObjectMapper mapper = new ObjectMapper(); \nPerson person = new Person(); \nperson.setName(\"Tom\"); \nperson.setAge(40); \nString jsonString = mapper.writerWithDefaultPrettyPrinter() \n .writeValueAsString(person); \nPerson deserializedPerson = mapper.readValue(jsonString, Person.class);","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" ","attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"ObjectMapper 通过 writeValue 系列方法 将 java 对 象序列化 为 json，并 将 json存储成不同的格式，String（writeValueAsString），Byte Array（writeValueAsString），Writer， File，OutStream 和 DataOutput。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" ObjectMapper 通过 readValue 系列方法从不同的数据源像 String ， Byte Array， Reader，File，URL， InputStream 将 json 反序列化为 java 对象。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"ObjectMapper的信息配置","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" 在调用 writeValue 或调用 readValue 方法之前，往往需要设置 ObjectMapper 的相关配置信息。这些配置信息应用 java 对象的所有属性上。示例如下：","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":5},"content":[{"type":"text","text":"配置信息使用示例","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"//在反序列化时忽略在 json 中存在但 Java 对象不存在的属性 \nmapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false); \n//在序列化时日期格式默认为 yyyy-MM-dd'T'HH:mm:ss.SSSZ \nmapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,false) \n//在序列化时忽略值为 null 的属性 \nmapper.setSerializationInclusion(Include.NON_NULL); \n//忽略值为默认值的属性 \nmapper.setDefaultPropertyInclusion(Include.NON_DEFAULT);","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"更多配置信息可以查看 Jackson 的 DeserializationFeature，SerializationFeature 和Include。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的注解使用","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson 根据它的默认方式序列化和反序列化 java 对象，若根据实际需要，灵活的调整它的默认方式，可以使用 Jackson 的注解。常用的注解及用法如下。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"Jackson的常用注解","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonProperty：用于属性，把属性的名称序列化时转换为另外一个名称。示例：@JsonProperty(\"birth_ d ate\") private Date birthDate;","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonFormat\t用于属性或者方法，把属性的格式序列化时转换成指定的格式。示例：@JsonFormat(timezone = \"GMT+8\", pattern = \"yyyy-MM-dd HH:mm\") public Date getBirthDate()","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonPropertyOrder 用于类， 指定属性在序列化时 json 中的顺序 ， 示例：@JsonPropertyOrder({ \"birth_Date\", \"name\" }) public class Person;","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonCreator\t用于构造方法，和 @JsonProperty 配合使用，适用有参数的构造方法。 示例：@JsonCreator public Person(@JsonProperty(\"name\")String name) {…}","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonAnySetter 用于属性或者方法，设置未反序列化的属性名和值作为键值存储到 map 中@JsonAnySetter public void set(String key, Object value) { map.put(key, value); }","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"@JsonAnyGetter 用于方法 ，获取所有未序列化的属性 public Map
any() { return map; }","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在了解 Jackson 的基本用法后，下面详细地介绍它的一些高阶应用。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson 的高阶应用","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"格式处理（含日期格式）","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"不同类型的日期类型，Jackson的处理方式也不同。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期类型： java.util.Calendar,java.util.GregorianCalendar,java.sql.Date,java.util.Date,java.sql.Timestamp，若不指定格式，在json文件中将序列化为long类型的数据。显然这种默认格式，可读性差，转换格式是必要的。Jackson有很多方式转换日期格式。注解方式，请参照\" Jackson 的注解的使用\"的@ JsonFormat 的示例。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ObjectMapper方式，调用ObjectMapper 的方法setDateFormat，将序列化为指定格式的 string 类型的数据。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期类型：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" java.time.LocalDate，还需要添加代码 mapper.registerModule(new JavaTimeModule())，同时添加相应的依赖 jar 包","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" \n com.fasterxml.jackson.datatype \n jackson-datatype-jsr310 \n 2.9.1 \n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"对于 Jackson 2.5 以下版本，需要添加代码 objectMapper.registerModule(new JSR310Module ())","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期类型：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"org.joda.time.DateTime","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"还需要添加代码 mapper.registerModule(new JodaModule())，同时添加相应的依赖 jar 包","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" \n com.fasterxml.jackson.datatype\n jackson-datatype-joda \n 2.9.1 \n","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"泛型反序列化","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" Jackson 对泛型反序列化也提供很好的支持。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 对于 List 类型 ，可以调用 constructCollectionType 方法来序列化，也可以构造 TypeReference 来序列化。","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"CollectionType javaType = mapper.getTypeFactory() \n .constructCollectionType(List.class, Person.class); \nList personList = mapper.readValue(jsonInString, javaType); \nList personList = mapper.readValue(jsonInString,new TypeReference>(){});","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"对于 map 类型， 与 List 的实现方式相似。","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"//第二参数是 map 的 key 的类型，第三参数是 map 的 value 的类型 \nMapType javaType =\n mapper.getTypeFactory().constructMapType(HashMap.class,String.class,\n Person.class); \n Map personMap = mapper.readValue(jsonInString, javaType); \n Map personMap = mapper.readValue(jsonInString,new TypeReference
{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的基本简介","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" ","attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson是当前用的比较广泛的，用来序列化和反序列化 json 的 Java 的开源框架。Jackson 社 区相对比较活跃，更新速度也比较快， 从 Github 中的统计来看，Jackson 是最流行的 json 解析器之一 。 Spring MVC 的默认json解析器便是 Jackson。","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 所依赖的 jar 包较少 ，简单易用。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 解析大的 json 文件速度比较快；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 运行时占用内存比较低，性能比较好；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"Jackson 有灵活的 API，可以很容易进行扩展和定制。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson 的 1.x 版本的包名是","attrs":{}},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"org.codehaus.jackson","attrs":{}}],"attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" ，当升级到 2.x 版本时，包名变为 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"com.fasterxml.jackson","attrs":{}}],"attrs":{}},{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"，本文讨论的内容是基于最新的 Jackson 的 2.9.1 版本。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的核心模块","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-core：核心包，提供基于\"流模式\"解析的相关 API，它包括 JsonParser 和 JsonGenerator。 Jackson 内部实现正是通过高性能的流模式 API 的 JsonGenerator 和 JsonParser 来生成和解析 json。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-annotations：注解包，提供标准注解功能；","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"strong","attrs":{}}],"text":"jackson-databind：数据绑定包， 提供基于\"对象绑定\" 解析的相关 API （ ObjectMapper ） 和\"树模型\" 解析的相关 API （JsonNode）；基于\"对象绑定\" 解析的 API 和\"树模型\"解析的 API 依赖基于\"流模式\"解析的 API。","attrs":{}}]}]}],"attrs":{}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson 的基本用法","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" 若想在 Java 代码中使用 Jackson 的核心模块的 jar 包 ，需要在 pom.xml 中添加如下信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":"清单 1.在 pom.xml 的 Jackson 的配置信息","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"