Java对象与Json之间的转换

使用Jackson的ObjectMapper对象的readValue和writeValueAsString方法可以进行转换。

对于简单基本类型或String类型的对象，使用上述方法可以满足。

但是如果要转换复杂类型Collection如 List<YourBean>，那么就需要先反序列化复杂类型为泛型的Collection Type。

如果是ArrayList<YourBean>那么使用ObjectMapper 的getTypeFactory().constructParametricType(collectionClass, elementClasses);

如果是HashMap<String,YourBean>那么 ObjectMapper 的getTypeFactory().constructParametricType(HashMap.class,String.class, YourBean.class);

例子如下，定义两个模型

 package com.khlin.com.khlin.jackson.json.test;

 import java.util.List;

 public class Student {

     private String familyname;

     private String lastname;

     private int age;

     private String[] familyMembers;

     private Place hometown;

     public Place getHometown() {
         return hometown;
     }

     public void setHometown(Place hometown) {
         this.hometown = hometown;
     }

     public List<Place> getFavoritePlaces() {
         return favoritePlaces;
     }

     public void setFavoritePlaces(List<Place> favoritePlaces) {
         this.favoritePlaces = favoritePlaces;
     }

     private List<Place> favoritePlaces;

     public String getFamilyname() {
         return familyname;
     }

     public void setFamilyname(String familyname) {
         this.familyname = familyname;
     }

     public String getLastname() {
         return lastname;
     }

     public void setLastname(String lastname) {
         this.lastname = lastname;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public String[] getFamilyMembers() {
         return familyMembers;
     }

     public void setFamilyMembers(String[] familyMembers) {
         this.familyMembers = familyMembers;
     }
 }

 package com.khlin.com.khlin.jackson.json.test;

 public class Place {

     private String province;

     private String city;

     public String getProvince() {
         return province;
     }

     public void setProvince(String province) {
         this.province = province;
     }

     public String getCity() {
         return city;
     }

     public void setCity(String city) {
         this.city = city;
     }
 }

转换代码：

 ObjectMapper objectMapper = new ObjectMapper();

         Place hometown = new Place();
         hometown.setProvince("guangdong");
         hometown.setCity("jieyang");

         Place place1 = new Place();
         place1.setProvince("fujian");
         place1.setCity("amoy");

         Place place2 = new Place();
         place2.setProvince("zhejiang");
         place2.setCity("hangzhou");

         List<Place> places = new ArrayList<Place>();
         places.add(place1);
         places.add(place2);
         Student student = generateStudent("dacui", "lin", hometown, places);

         Student student2 = generateStudent("ku", "lee", hometown, places);

         List<Student> students = new ArrayList<Student>();
         students.add(student);
         students.add(student2);

         String result = objectMapper.writeValueAsString(students);
         System.out.println(result);

         JavaType javaType = objectMapper.getTypeFactory()
                 .constructParametricType(ArrayList.class, Student.class);

         List<Student> mapperStudents = objectMapper.readValue(result,
                 javaType);
         Student mapperStudent1 = mapperStudents.get(0);
         Student mapperStudent2 = mapperStudents.get(1);
         System.out.println("success");