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{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的基本簡介","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是當前用的比較廣泛的，用來序列化和反序列化 json 的 Java 的開源框架。Jackson 社 區相對比較活躍，更新速度也比較快， 從 Github 中的統計來看，Jackson 是最流行的 json 解析器之一 。 Spring MVC 的默認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 所依賴的 jar 包較少 ，簡單易用。","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 文件速度比較快；","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 運行時佔用內存比較低，性能比較好；","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 有靈活的 API，可以很容易進行擴展和定製。","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":" ，當升級到 2.x 版本時，包名變爲 ","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":"，本文討論的內容是基於最新的 Jackson 的 2.9.1 版本。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的核心模塊","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，提供基於\"流模式\"解析的相關 API，它包括 JsonParser 和 JsonGenerator。 Jackson 內部實現正是通過高性能的流模式 API 的 JsonGenerator 和 JsonParser 來生成和解析 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：註解包，提供標準註解功能；","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：數據綁定包， 提供基於\"對象綁定\" 解析的相關 API （ ObjectMapper ） 和\"樹模型\" 解析的相關 API （JsonNode）；基於\"對象綁定\" 解析的 API 和\"樹模型\"解析的 API 依賴基於\"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 代碼中使用 Jackson 的核心模塊的 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":"清單 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 依賴 jackson-core 和 jackson-annotations，當添加 jackson-databind 之後， jackson-core 和 jackson-annotations 也隨之添加到 Java 項目工程中。在添加相關依賴包之後，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 就是基於\"對象綁定\" 的 ObjectMapper。下面是一個 ObjectMapper 的使用的簡單示例。","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 通過 writeValue 系列方法 將 java 對 象序列化 爲 json，並 將 json存儲成不同的格式，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 通過 readValue 系列方法從不同的數據源像 String ， Byte Array， Reader，File，URL， InputStream 將 json 反序列化爲 java 對象。","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":" 在調用 writeValue 或調用 readValue 方法之前，往往需要設置 ObjectMapper 的相關配置信息。這些配置信息應用 java 對象的所有屬性上。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":"//在反序列化時忽略在 json 中存在但 Java 對象不存在的屬性 \nmapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false); \n//在序列化時日期格式默認爲 yyyy-MM-dd'T'HH:mm:ss.SSSZ \nmapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,false) \n//在序列化時忽略值爲 null 的屬性 \nmapper.setSerializationInclusion(Include.NON_NULL); \n//忽略值爲默認值的屬性 \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的註解使用","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}}],"text":" Jackson 根據它的默認方式序列化和反序列化 java 對象，若根據實際需要，靈活的調整它的默認方式，可以使用 Jackson 的註解。常用的註解及用法如下。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"Jackson的常用註解","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：用於屬性，把屬性的名稱序列化時轉換爲另外一個名稱。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用於屬性或者方法，把屬性的格式序列化時轉換成指定的格式。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 用於類， 指定屬性在序列化時 json 中的順序 ， 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用於構造方法，和 @JsonProperty 配合使用，適用有參數的構造方法。 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 用於屬性或者方法，設置未反序列化的屬性名和值作爲鍵值存儲到 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 用於方法 ，獲取所有未序列化的屬性 public Map
any() { return map; }","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在瞭解 Jackson 的基本用法後，下面詳細地介紹它的一些高階應用。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson 的高階應用","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"格式處理（含日期格式）","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"不同類型的日期類型，Jackson的處理方式也不同。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期類型： java.util.Calendar,java.util.GregorianCalendar,java.sql.Date,java.util.Date,java.sql.Timestamp，若不指定格式，在json文件中將序列化爲long類型的數據。顯然這種默認格式，可讀性差，轉換格式是必要的。Jackson有很多方式轉換日期格式。註解方式，請參照\" Jackson 的註解的使用\"的@ JsonFormat 的示例。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ObjectMapper方式，調用ObjectMapper 的方法setDateFormat，將序列化爲指定格式的 string 類型的數據。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期類型：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" java.time.LocalDate，還需要添加代碼 mapper.registerModule(new JavaTimeModule())，同時添加相應的依賴 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":"對於 Jackson 2.5 以下版本，需要添加代碼 objectMapper.registerModule(new JSR310Module ())","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"日期類型：","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":"還需要添加代碼 mapper.registerModule(new JodaModule())，同時添加相應的依賴 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 對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":" 對於 List 類型 ，可以調用 constructCollectionType 方法來序列化，也可以構造 TypeReference 來序列化。","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":"對於 map 類型， 與 List 的實現方式相似。","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"//第二參數是 map 的 key 的類型，第三參數是 map 的 value 的類型 \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的基本簡介","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是當前用的比較廣泛的，用來序列化和反序列化 json 的 Java 的開源框架。Jackson 社 區相對比較活躍，更新速度也比較快， 從 Github 中的統計來看，Jackson 是最流行的 json 解析器之一 。 Spring MVC 的默認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 所依賴的 jar 包較少 ，簡單易用。","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 文件速度比較快；","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 運行時佔用內存比較低，性能比較好；","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 有靈活的 API，可以很容易進行擴展和定製。","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":" ，當升級到 2.x 版本時，包名變爲 ","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":"，本文討論的內容是基於最新的 Jackson 的 2.9.1 版本。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Jackson的核心模塊","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，提供基於\"流模式\"解析的相關 API，它包括 JsonParser 和 JsonGenerator。 Jackson 內部實現正是通過高性能的流模式 API 的 JsonGenerator 和 JsonParser 來生成和解析 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：註解包，提供標準註解功能；","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：數據綁定包， 提供基於\"對象綁定\" 解析的相關 API （ ObjectMapper ） 和\"樹模型\" 解析的相關 API （JsonNode）；基於\"對象綁定\" 解析的 API 和\"樹模型\"解析的 API 依賴基於\"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 代碼中使用 Jackson 的核心模塊的 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":"清單 1.在 pom.xml 的 Jackson 的配置信息","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"