Jackson使用示例-Bean、XML、Json之間相互轉換

更新時間：2024年05月18日 09:36:34 作者：秋一葉葉

Jackson是一個強大工具,可用于Json、XML、實體之間的相互轉換,JacksonXmlElementWrapper用于指定List等集合類,外圍標簽名,JacksonXmlProperty指定包裝標簽名,或者指定標簽內部屬性名,JacksonXmlRootElement指定生成xml根標簽的名字,JacksonXmlText指定當前這個值

前言

目前常見的json解析工具有jackson、fastjson、gson。

jackson是Spring mvc內置的json轉換工具；
fastjson是阿里的開源JSON解析庫，由于fastjson經常會出現(xiàn)漏洞，暫不考慮；
Jackson是一個強大工具，可用于Json、XML、實體之間的相互轉換。

Jackson相關注解

注解	說明
@JsonProperties	把屬性的名稱序列化時轉換為另外一個名稱；@JsonProperty(“DepName”)
@JsonFormat	把屬性的格式序列化時轉換成指定的格式；@JsonFormat(pattern = “yyyy-MM-dd”)
@JsonPropertyOrder	指定屬性在序列化時 json 中的順序；@JsonPropertyOrder({ “age”, “name” })
@JsonIgnore	排除指定屬性不被json序列化
@JacksonXmlProperty	指定XML命名空間的名稱；@JacksonXmlProperty(localName = “DepName”)
@JacksonXmlRootElement	指定XML根元素命名空間的名稱；@JacksonXmlRootElement(localName = “RootName”)
@JacksonXmlElementWrapper	可用于指定List等集合類，外圍標簽名；@JacksonXmlElementWrapper(localName = “EmpMessage”)

1、對象和json互轉

引入jackson相關依賴：

<!--注解包，提供標準注解功能-->
<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
</dependency>
<!--核心包，提供基于"流模式"解析的相關 API-->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
</dependency>
<!--數(shù)據(jù)綁定包，提供基于"對象綁定" 解析的相關 API （ ObjectMapper ） 和"樹模型" 解析的相關 API-->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>
<!--日期類型序列化包-->
<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實體類：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Employees {
    private String name;
    private Integer age;
    private String sex;
}

測試代碼：

/**
 * @author 秋一葉
 * @create 2024-04-23 21:00
 * json字符串和對象、集合、map互轉
 *
 */
public class Demo2 {
    public static void main(String[] args) {
   		ObjectMapper objectMapper = new ObjectMapper();
        Employees employees1 = new Employees("秋一葉",18,"男");
        Employees employees2 = new Employees("小王",20,"男");
        
        try {
            //對象轉json字符串
            String jsonString = objectMapper.writeValueAsString(employees1);
            //json字符串轉為對象
            Employees emp1 = objectMapper.readValue(jsonString, Employees.class);
            System.out.println("json字符串：" + jsonString);
            System.out.println("對象1：" + emp1);

            System.out.println("====================================================");

            //對象轉為json字符串寫入文件
            objectMapper.writeValue(new File("emp.json"), employees1);
            //從文件中讀取json字符串轉為對象
            Employees emp2 = objectMapper.readValue(new File("emp.json"), Employees.class);
            System.out.println("對象2：" + emp2);

            System.out.println("====================================================");

            //對象寫為字節(jié)流
            byte[] bytes = objectMapper.writeValueAsBytes(employees1);
            //字節(jié)流轉為對象
            Employees emp3 = objectMapper.readValue(bytes, Employees.class);
            System.out.println("對象3：" + emp3);

            System.out.println();
            System.out.println("*****************************************************");
            System.out.println();


            //Map和json互轉
            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互轉
            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();
        }
    }
}

打印結果：

json字符串：{"name":"秋一葉","age":18,"sex":"男"}
對象1：Employees(name=秋一葉, age=18, sex=男)
====================================================
對象2：Employees(name=秋一葉, age=18, sex=男)
====================================================
對象3：Employees(name=秋一葉, age=18, sex=男)

*****************************************************

json字符串：{"001":{"name":"秋一葉","age":18,"sex":"男"},"002":"元旦"}
map：{001={name=秋一葉, age=18, sex=男}, 002=元旦}
====================================================
json字符串：[{"name":"秋一葉","age":18,"sex":"男"},{"name":"小王","age":20,"sex":"男"}]
map：[Employees(name=秋一葉, age=18, sex=男), Employees(name=小王, age=20, sex=男)]

2、XML和對象互轉

Department實體：

@Data
@JacksonXmlRootElement(localName = "RootName")
public class Department {
    @JacksonXmlProperty(localName = "DepName")
    private String depName;
    
    @JacksonXmlElementWrapper(localName = "EmpMessage")
    @JacksonXmlProperty(localName = "EmpName")
    List<Employees> employees; 
}

測試代碼：

public class Demo1 {
    public static void main(String[] args) {
        XmlMapper xmlMapper = new XmlMapper();
        //字段為null，自動忽略，不再序列化
        xmlMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

        Department department = new Department();
        Employees employees1 = new Employees("秋一葉",18,"男");
        Employees employees2 = new Employees("小王",20,"男");
        department.setDepName("產品研發(fā)部門");
        department.setEmployees(Lists.newArrayList(employees1, employees2));

        try {
            //對象轉xml
            String xml = xmlMapper.writeValueAsString(department);
            //xml轉對象
            Department dep = xmlMapper.readValue(xml, Department.class);

            System.out.println("返回的xml：" + xml);
            System.out.println("返回的實體：" + dep);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
    }
}

打印結果：

返回的xml：<RootName><DepName>產品研發(fā)部門</DepName><EmpMessage><EmpName><name>秋一葉</name><age>18</age><sex>男</sex></EmpName><EmpName><name>小王</name><age>20</age><sex>男</sex></EmpName></EmpMessage></RootName>
返回的實體：Department(depName=產品研發(fā)部門, employees=[Employees(name=秋一葉, age=18, sex=男), Employees(name=小王, age=20, sex=男)])

Jackson使用示例-Bean、XML、Json互轉_jackson