java - Jackson:反序列化 ArrayList 不起作用？

Question

我指的是这个例子here序列化我的对象。

我最初有这个并且它有效。

public class MyClass implements Serializable {
    private String mediaitem_id;
    private String customer_id;
    private int quantity;

    public MyClass(String item, String customer, int quantity){
        this.mediaitem_id = item;
        this.customer_id = customer;
        this.quantity = quantity;    
    }

    public String toJson(){
        ObjectMapper mapper = new ObjectMapper();

        try{
            mapper.setPropertyNamingStrategy(PropertyNamingStrategy.LOWER_CASE);
            return mapper.writeValueAsString(this);
        }catch(Exception ex){
            log.error("Error converting MyClass to json " + this, ex);
        }

        return "";
    }
}

MyClass myClass = new MyClass("1234", "23234", 5);

myClass.toJson() 给出以下内容，这就是我想要的:

{ mediaitem_id: '1234', customer_id: '23234', quantity: 5 }

但是现在我需要向类中添加一个数组列表，并且还需要对其进行序列化，因此我添加了一个新类 Account:

public static class Account implements Serializable {
    public String accountname;
    public String accountid;

    public Account(String accountname, String accountid) {
        this.accountname = accountname;
        this.accountid = accountid;
    }
}

public class MyClass implements Serializable {
    private String mediaitem_id;
    private String customer_id;
    private int quantity;
    private List<Account> accounts = new ArrayList<>();

    public MyClass(String item, String customer, int quantity){
        this.mediaitem_id = item;
        this.customer_id = customer;
        this.quantity = quantity;    
    }

    public void addAccount(String accountname, String accountid) {
        Account anAccount = new Account(accountname, accountid);
        accounts.add(anAccount);
    }       

    public String toJson(){
        ObjectMapper mapper = new ObjectMapper();

        try{
            mapper.setPropertyNamingStrategy(PropertyNamingStrategy.LOWER_CASE);
            return mapper.writeValueAsString(this);
        }catch(Exception ex){
            log.error("Error converting MyClass to json " + this, ex);
        }

        return "";
    }
}

MyClass myClass = new MyClass("1234", "23234", 5);
myClass.addAccount("acc-01", "a001");
myClass.addAccount("acc-02", "a002");

myClass.toJson() 仍然给出相同的结果:

{ mediaitem_id: '1234', customer_id: '23234', quantity: 5 }

我现在缺少什么？

我想要得到类似的东西:

{ mediaitem_id: '1234', customer_id: '23234', quantity: 5, accounts: [{accountname: 'acc-01', accountid: 'a001'}, {accountname: 'acc-02', accountid: 'a002'}]}

Answer 1

我建议为 MyClass 中的所有属性添加 getter 和 setter。

public String getMediaitem_id() {
        return mediaitem_id;
    }

    public void setMediaitem_id(String mediaitem_id) {
        this.mediaitem_id = mediaitem_id;
    }

    public String getCustomer_id() {
        return customer_id;
    }

    public void setCustomer_id(String customer_id) {
        this.customer_id = customer_id;
    }

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    public List<Account> getAccounts() {
        return accounts;
    }

    public void setAccounts(List<Account> accounts) {
        this.accounts = accounts;
    }