Java下常見的Json類庫有Gson、JSON-lib和Jackson等，Jackson相對(duì)來說比較高效，在項(xiàng)目中主要使用Jackson進(jìn)行JSON和Java對(duì)象轉(zhuǎn)換，下面給出一些Jackson的JSON操作方法。

一、準(zhǔn)備工作

Jackson有1.x系列和2.x系列，2.x系列有3個(gè)jar包需要下載：
jackson-core-2.2.3.jar（核心jar包）
jackson-annotations-2.2.3.jar（該包提供Json注解支持）
jackson-databind-2.2.3.jar

一個(gè)maven依賴就夠了

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.5.3</version> </dependency> import java.util.Date;/*** JSON序列化和反序列化使用的User類*/ public class User {private String name;private Integer age;private Date birthday;private String email;public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "User{" +"name='" + name + '\'' +", age=" + age +", birthday=" + birthday +", email='" + email + '\'' +'}';} }

二、JAVA對(duì)象轉(zhuǎn)JSON[JSON序列化]

import java.io.IOException; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.List; import com.fasterxml.jackson.databind.ObjectMapper;public class JacksonDemo {public static void main(String[] args) throws ParseException, IOException {User user = new User();user.setName("zhangsan");user.setEmail("zhangsan@163.com");user.setAge(20);SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd");user.setBirthday(dateformat.parse("1996-10-01"));/*** ObjectMapper是JSON操作的核心，Jackson的所有JSON操作都是在ObjectMapper中實(shí)現(xiàn)。* ObjectMapper有多個(gè)JSON序列化的方法，可以把JSON字符串保存File、OutputStream等不同的介質(zhì)中。* writeValue(File arg0, Object arg1)把a(bǔ)rg1轉(zhuǎn)成json序列，并保存到arg0文件中。* writeValue(OutputStream arg0, Object arg1)把a(bǔ)rg1轉(zhuǎn)成json序列，并保存到arg0輸出流中。* writeValueAsBytes(Object arg0)把a(bǔ)rg0轉(zhuǎn)成json序列，并把結(jié)果輸出成字節(jié)數(shù)組。* writeValueAsString(Object arg0)把a(bǔ)rg0轉(zhuǎn)成json序列，并把結(jié)果輸出成字符串。*/ObjectMapper mapper = new ObjectMapper();//User類轉(zhuǎn)JSON//輸出結(jié)果：{"name":"zhangsan","age":20,"birthday":844099200000,"email":"zhangsan@163.com"}String json = mapper.writeValueAsString(user);System.out.println(json);//Java集合轉(zhuǎn)JSON//輸出結(jié)果：[{"name":"zhangsan","age":20,"birthday":844099200000,"email":"zhangsan@163.com"}]List<User> users = new ArrayList<User>();users.add(user);String jsonlist = mapper.writeValueAsString(users);System.out.println(jsonlist);} }

三、JSON轉(zhuǎn)Java類[JSON反序列化]

public class JacksonDemo {public static void main(String[] args) throws ParseException, IOException {String json = "{\"name\":\"zhangsan\",\"age\":20,\"birthday\":844099200000,\"email\":\"zhangsan@163.com\"}";/*** ObjectMapper支持從byte[]、File、InputStream、字符串等數(shù)據(jù)的JSON反序列化。*/ObjectMapper mapper = new ObjectMapper();User user = mapper.readValue(json, User.class);System.out.println(user);} }

結(jié)果

User{name='zhangsan', age=20, birthday=Tue Oct 01 00:00:00 CST 1996, email='zhangsan@163.com'} public class JacksonDemo {public static ObjectMapper mapper = new ObjectMapper();public static void main(String[] args) throws ParseException, IOException {String json = "[{\"name\":\"zhangsan\",\"age\":20,\"birthday\":844099200000,\"email\":\"zhangsan@163.com\"}]";List<User> beanList = mapper.readValue(json, new TypeReference<List<User>>() {});System.out.println(beanList);}}

結(jié)果

[User{name='zhangsan', age=20, birthday=Tue Oct 01 00:00:00 CST 1996, email='zhangsan@163.com'}]

四、JSON注解

Jackson提供了一系列注解，方便對(duì)JSON序列化和反序列化進(jìn)行控制，下面介紹一些常用的注解。
@JsonIgnore 此注解用于屬性上，作用是進(jìn)行JSON操作時(shí)忽略該屬性。
@JsonFormat 此注解用于屬性上，作用是把Date類型直接轉(zhuǎn)化為想要的格式，如@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")。
@JsonProperty 此注解用于屬性上，作用是把該屬性的名稱序列化為另外一個(gè)名稱，如把trueName屬性序列化為name，@JsonProperty("name")。

import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.annotation.JsonIgnore; import com.fasterxml.jackson.annotation.JsonProperty;import java.util.Date;/*** JSON序列化和反序列化使用的User類*/ public class User {private String name;//不JSON序列化年齡屬性 @JsonIgnoreprivate Integer age;//格式化日期屬性@JsonFormat(pattern = "yyyy年MM月dd日")private Date birthday;//序列化email屬性為mail@JsonProperty("my_email")private String email;public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "User{" +"name='" + name + '\'' +", age=" + age +", birthday=" + birthday +", email='" + email + '\'' +'}';} } import com.fasterxml.jackson.databind.ObjectMapper; import java.io.IOException; import java.text.ParseException; import java.text.SimpleDateFormat;public class JacksonDemo {public static void main(String[] args) throws ParseException, IOException {User user = new User();user.setName("zhangsan");user.setEmail("zhangsan@163.com");user.setAge(20);SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd");user.setBirthday(dateformat.parse("1996-10-01"));ObjectMapper mapper = new ObjectMapper();String json = mapper.writeValueAsString(user);System.out.println(json);} } {"name":"zhangsan","birthday":"1996年09月30日","my_email":"zhangsan@163.com"}

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本文轉(zhuǎn)載自網(wǎng)絡(luò)，本文僅用于個(gè)人學(xué)習(xí)記錄及備忘

轉(zhuǎn)載于:https://www.cnblogs.com/xiwai/p/10138328.html

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