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");