markdown
## Json简述
#### 数组
```text
[test,a,demo,123]
```
#### 对象
```text
{
"id":1,
"salary":5000.0,
"annualSalary":60000.0,
"name":"halrod",
"city":12,
"entryTime":"2023/05/08 10/23/24"
}
```
#### 相互嵌套
```text
[
{"id":1,
"salary":5000.0,
"annualSalary":60000.0,
"name":"halrod",
"city":12,
"entryTime":"2023/05/08 10/23/24"
},{"id":3,
"salary":53634.0,
"annualSalary":643608.0,
"name":"dashwood",
"city":23,
"entryTime":"2023/05/09 00/31/33"
},{"id":23,
"salary":34443.0,
"annualSalary":413316.0,
"name":"demo",
"city":64,
"entryTime":"2023/05/09 05/37/38"
}
]
```
## spring Jackson
Jackson 依赖于 mvc 包
```text
org.springframework.boot
spring-boot-starter-web
```
### 注解
```text
#格式化LocaldateTime
@JsonFormat(pattern = "yyyy/MM/dd HH/mm/ss", timezone = "GMT-8")
#将pojo装换成ResponseBody时隐藏该字段
@JsonIgnore
#将pojo装换成ResponseBody时更改该字段名称
@JsonProperty("城市代号")
#如果为空将不显示
@JsonInclude(JsonInclude.Include.NON_NULL)
#重新定义pojo字段顺序
@JsonPropertyOrder(value = {"id","name","salary","annualSalary","city","entryTime"})
```
### 对象转换
#### pojo转Json
```text
ObjectMapper objectMapper = new ObjectMapper();
try {
objectMapper.findAndRegisterModules();
String s = objectMapper.writeValueAsString(对象list);
} catch (JsonProcessingException e) {
throw new RuntimeException(e);
}
```
#### Json转pojo
```text
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.readValue("jsonstring",目标对象.class)
```
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