您当前的位置： 首页 > 慢生活 > 程序人生 网站首页程序人生

14_JSON_解析器Jackson_json转Java对象

发布时间：2022-10-01 12:11:59编辑：雪饮阅读（）

以上篇最终的hashMap转出去的json字符串为例：

这里是为了演示将json字符串转回到java对象。

这里需要预备一个java类，由于这个待转换的字符串里面有company1和company2，所以我们要预备的这个java类需要有company1和company2这两个getter和setter的方法，并且要有默认无参构造，对应的这个json字符串里面每个company1或company2是对应我们的company类，则company类也最好有无参构造，那么对应的person则更不必说了。

为什么需要无参构造？，人家转换成java对象时候，如何给你构造？他又不知道你每个构造怎样传参，我觉得人家肯定是通过getter和setter来判断的。

除了无参构造，相关类最好也有自己的toString方法，否则转换完成后只能看到java对象的地址值，而不能看到实际数据。

所以person类调整如：

package package3.servlet;

public class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Person() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

company类调整如：

package package3.servlet;
 
 import com.fasterxml.jackson.annotation.JsonFormat;
 
 import java.util.ArrayList;
 import java.util.Date;
 
 public class Company {
     private String company_name;
     private double salary;
     private ArrayList<Person> persons;
     private Person legalPerson;
     private Date register_date;
 
     public Company(String company_name, double salary, ArrayList<Person> persons, Person legalPerson, Date register_date) {
         this.company_name = company_name;
         this.salary = salary;
         this.persons = persons;
         this.legalPerson = legalPerson;
         this.register_date = register_date;
     }
 
     public Company() {
     }
 
 
     public String getCompany_name() {
         return company_name;
     }
 
     public void setCompany_name(String company_name) {
         this.company_name = company_name;
     }
 
     public double getSalary() {
         return salary;
     }
 
     public void setSalary(double salary) {
         this.salary = salary;
     }
 
     public ArrayList<Person> getPersons() {
         return persons;
     }
 
     public void setPersons(ArrayList<Person> persons) {
         this.persons = persons;
     }
 
     public Person getLegalPerson() {
         return legalPerson;
     }
 
     public void setLegalPerson(Person legalPerson) {
         this.legalPerson = legalPerson;
     }
     @JsonFormat(pattern="yyyy-MM-dd")
     public Date getRegister_date() {
         return register_date;
     }
 
     public void setRegister_date(Date register_date) {
         this.register_date = register_date;
     }
 
     @Override
     public String toString() {
         return "Company{" +
                 "company_name='" + company_name + '\'' +
                 ", salary=" + salary +
                 ", persons=" + persons +
                 ", legalPerson=" + legalPerson +
                 ", register_date=" + register_date +
                 '}';
     }
 }

我们需要新建的一个容下company1和company2的类BigCompany类如：

package package3.servlet;
 
 public class BigCompany {
     private Company company1;
     private Company company2;
 
     public Company getCompany1() {
         return company1;
     }
 
     public Company getCompany2() {
         return company2;
     }
 
     @Override
     public String toString() {
         return "BigCompany{" +
                 "company1=" + company1 +
                 ", company2=" + company2 +
                 '}';
     }
 }

最后我们实现json字符串转java对象的servlet如：

package package3.servlet;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 @WebServlet("/ServletTest")
 public class ServletTest extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         ObjectMapper objectMapper = new ObjectMapper();
 
         String json_str="{\"company1\":{\"company_name\":\"韦恩企业\",\"salary\":130000.0,\"persons\":[{\"name\":\"雪饮\",\"age\":24},{\"name\":\"布鲁斯韦恩\",\"age\":28},{\"name\":\"murphy pendleton\",\"age\":24},{\"name\":\"kasumi\",\"age\":28}],\"legalPerson\":{\"name\":\"布鲁斯韦恩\",\"age\":28},\"register_date\":\"2022-10-01\"},\"company2\":{\"company_name\":\"雪饮网络科技\",\"salary\":150000.0,\"persons\":[{\"name\":\"雪饮\",\"age\":24},{\"name\":\"布鲁斯韦恩\",\"age\":28},{\"name\":\"murphy pendleton\",\"age\":24},{\"name\":\"kasumi\",\"age\":28}],\"legalPerson\":{\"name\":\"kasumi\",\"age\":28},\"register_date\":\"2022-10-01\"}}";
 
         response.setContentType("text/html;charset=utf-8");
         response.getWriter().write(objectMapper.readValue(json_str,BigCompany.class).toString());
     }
 
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         this.doPost(request, response);
     }
 }