前言
目前常见的json解析工具有jackson、fastjson、gson。
- jackson是Spring mvc内置的json转换工具；
- fastjson是阿里的开源JSON解析库，由于fastjson经常会出现漏洞，暂不考虑；
Jackson相关注解
注解 | 说明 |
@JsonProperties | 把属性的名称序列化时转换为另外一个名称 ；@JsonProperty(“DepName”) |
@JsonFormat | 把属性的格式序列化时转换成指定的格式；@JsonFormat(pattern = “yyyy-MM-dd”) |
@JsonPropertyOrder | 指定属性在序列化时 json 中的顺序；@JsonPropertyOrder({ “age”, “name” }) |
@JsonIgnore | 排除指定属性不被json序列化 |
@JacksonXmlProperty | 指定XML命名空间的名称；@JacksonXmlProperty(localName = “DepName”) |
@JacksonXmlRootElement | 指定XML根元素命名空间的名称；@JacksonXmlRootElement(localName = “RootName”) |
@JacksonXmlElementWrapper | 可用于指定List等集合类，外围标签名；@JacksonXmlElementWrapper(localName = “EmpMessage”) |
1、对象和json互转
引入jackson相关依赖：
<!--注解包，提供标准注解功能-->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
</dependency>
<!--核心包，提供基于"流模式"解析的相关 API-->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
</dependency>
<!--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-->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
<!--日期类型序列化包-->
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>
<!--引入xml功能-->
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
</dependency>Employees实体类：
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Employees {
private String name;
private Integer age;
private String sex;
}测试代码：
/**
* @author 秋一叶
* @create 2024-04-23 21:00
* json字符串和对象、集合、map互转
*
*/
public class Demo2 {
public static void main(String[] args) {
ObjectMapper objectMapper = new ObjectMapper();
Employees employees1 = new Employees("秋一叶",18,"男");
Employees employees2 = new Employees("小王",20,"男");
try {
//对象转json字符串
String jsonString = objectMapper.writeValueAsString(employees1);
//json字符串转为对象
Employees emp1 = objectMapper.readValue(jsonString, Employees.class);
System.out.println("json字符串：" + jsonString);
System.out.println("对象1：" + emp1);
System.out.println("====================================================");
//对象转为json字符串写入文件
objectMapper.writeValue(new File("emp.json"), employees1);
//从文件中读取json字符串转为对象
Employees emp2 = objectMapper.readValue(new File("emp.json"), Employees.class);
System.out.println("对象2：" + emp2);
System.out.println("====================================================");
//对象写为字节流
byte[] bytes = objectMapper.writeValueAsBytes(employees1);
//字节流转为对象
Employees emp3 = objectMapper.readValue(bytes, Employees.class);
System.out.println("对象3：" + emp3);
System.out.println();
System.out.println("*****************************************************");
System.out.println();
//Map和json互转
Map<String, Object> map = Maps.newHashMap();
map.put("001", employees1);
map.put("002", "元旦");
String mapToString = objectMapper.writeValueAsString(map);
Map<String, Object> stringToMap = objectMapper.readValue(mapToString, new TypeReference<Map<String, Object>>() {
});
System.out.println("json字符串：" + mapToString);
System.out.println("map：" + stringToMap);
System.out.println("====================================================");
//List和json互转
List<Employees> empList = Lists.newArrayList(employees1, employees2);
String jsonList = objectMapper.writeValueAsString(empList);
List<Employees> stringToList = objectMapper.readValue(jsonList, new TypeReference<List<Employees>>() {
});
System.out.println("json字符串：" + jsonList);
System.out.println("map：" + stringToList);
} catch (IOException e) {
e.printStackTrace();
}
}
}打印结果：
json字符串：{"name":"秋一叶","age":18,"sex":"男"}
对象1：Employees(name=秋一叶, age=18, sex=男)
====================================================
对象2：Employees(name=秋一叶, age=18, sex=男)
====================================================
对象3：Employees(name=秋一叶, age=18, sex=男)
*****************************************************
json字符串：{"001":{"name":"秋一叶","age":18,"sex":"男"},"002":"元旦"}
map：{001={name=秋一叶, age=18, sex=男}, 002=元旦}
====================================================
json字符串：[{"name":"秋一叶","age":18,"sex":"男"},{"name":"小王","age":20,"sex":"男"}]
map：[Employees(name=秋一叶, age=18, sex=男), Employees(name=小王, age=20, sex=男)]2、XML和对象互转
Department实体：
@Data
@JacksonXmlRootElement(localName = "RootName")
public class Department {
@JacksonXmlProperty(localName = "DepName")
private String depName;
@JacksonXmlElementWrapper(localName = "EmpMessage")
@JacksonXmlProperty(localName = "EmpName")
List<Employees> employees;
}测试代码：
public class Demo1 {
public static void main(String[] args) {
XmlMapper xmlMapper = new XmlMapper();
//字段为null，自动忽略，不再序列化
xmlMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
Department department = new Department();
Employees employees1 = new Employees("秋一叶",18,"男");
Employees employees2 = new Employees("小王",20,"男");
department.setDepName("产品研发部门");
department.setEmployees(Lists.newArrayList(employees1, employees2));
try {
//对象转xml
String xml = xmlMapper.writeValueAsString(department);
//xml转对象
Department dep = xmlMapper.readValue(xml, Department.class);
System.out.println("返回的xml：" + xml);
System.out.println("返回的实体：" + dep);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
}打印结果：
返回的xml：<RootName><DepName>产品研发部门</DepName><EmpMessage><EmpName><name>秋一叶</name><age>18</age><sex>男</sex></EmpName><EmpName><name>小王</name><age>20</age><sex>男</sex></EmpName></EmpMessage></RootName>
返回的实体：Department(depName=产品研发部门, employees=[Employees(name=秋一叶, age=18, sex=男), Employees(name=小王, age=20, sex=男)])
