// pom依赖
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.8</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.8</version>
</dependency>Jackson's use of readValue and write
1.定义一个User对象
public class User {
private String name;
private int age;
private Date birthday; // 没有使用jackson注解将会变成时间戳
private String email;
public User(String name, int age, Date birthday, String email) {
this.name = name;
this.age = age;
this.birthday = birthday;
this.email = 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;
}
}
2.使用jackson 的ObjectMapper 类中的 readValue()方法进行转换
public class JsonTest
{
public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
User user=new User("隔壁老王", 18, new Date(), "110");
User user1=new User("隔壁老王", 18, new Date(), "110");
List<User> list = new ArrayList<User>();
list.add(user);
list.add(user1);
//转换器
ObjectMapper mapper = new ObjectMapper();
// 对象--json数据
String json=mapper.writeValueAsString(user); //将对象转换成json
// 将json 字符串转成User类
User u = mapper.readValue(json, User.class);
// 将json 字符串转化成List<User>
List<User> list1 = mapper.readValue(list, new TypeReference<List<People>>(){}f)
// 其他的如将文件中转化成类的方法也相识 如
// readValue(File src, TypeReference valueTypeRef)
// readValue(File src, Class<T> valueType)
}
}
3.使用jackson 的ObjectMapper 类中的 writerValue()方法进行转换
public class JsonTest
{
public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd");
User user=new User("隔壁老王", 18, dateformat.parse("1996-10-01"), "110");
//转换器
ObjectMapper mapper = new ObjectMapper();
//User类转JSON 字符串
String json = mapper.writeValueAsString(user);
System.out.println(json);
//Java集合转JSON 字符串
List<User> users = new ArrayList<User>();
users.add(user);
String jsonlist = mapper.writeValueAsString(users);
System.out.println(jsonlist);
}
}
}
4.使用jackson ObjectMapper获取具体json 字符串中某个key值对于的value
// 假设 json字符串格式为 {content:{rendered: "23"}, titile:{rendered: "别跑"}} 则获取方式如下：
ObjectMapper mapper = new ObjectMapper();
mapper.readTree(content).forEach(jsonNode -> {
String renderedContent = jsonNode.path("content").path("rendered").asText("");
String title = jsonNode.path("title").path("rendered").asText("");
});
5.使用jackson 的提供了一系列注解
@JsonIgnore 此注解用于属性上，作用是进行JSON操作时忽略该属性。
@JsonFormat 此注解用于属性上，作用是把Date类型直接转化为想要的格式，如@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")。
@JsonProperty 此注解用于属性上，作用是把该属性的名称序列化为另外一个名称，如把trueName属性序列化Link: https: //www.jianshu.com/p/7e4bc9a535c8
Jackson notes and common usage
Recently wrote the project, use some of Jackson's notes, to sum up, to help you to remember.
1. @ JsonIgnore and @JsonIgnoreProperties
After two annotations may choose to use compared to controls:
@JsonIgnore
When json serialization java bean in some of the properties ignored , serialization and de-serialization are affected.
private String name;
private Integer age;
@JsonIgnore
private String color;
Print run in the console method
System.out.println(name+""+age+""+color+"");
Will only show the name and age, color is not affected notes are displayed.
Use Method: General marking property or method on, json returned data, i.e. does not contain the property.
@JsonIgnoreProperties
And the role of @JsonIgnore the same, which attributes are told that Jackson ignored,
Except @JsonIgnoreProperties is class level and may specify a plurality of attributes simultaneously.
@JsonIgnoreProperties(value = {"age","color"})
public class TestJackson {
private String id;
private String username;
private String password;
private Integer age;
private String color;
}
Class age and color attributes will be ignored during serialization and de-serialization.
2.@JsonProperty
It is used on the property, the role of the name of the attribute name sequence into another
@JsonProperty（"name"）
private String username;
The username attribute is serialized as name
3.@JsonInclude(JsonInclude.Include.NON_NULL)
This annotation indicates, if the value is null, is not returned , the annotations may be added on the class, the entity class json when the mutual conversion, the attribute value is null does not participate in serialization .
@JsonInclude(JsonInclude.Include.NON_NULL)
public Vector children;
@JsonInclude(JsonInclude.Include.NON_NULL)
public class TestJackson {
xxxxxx
}
Links: https://www.cnblogs.com/koudaiyoutang/p/9709806.html