Question

我有一个jsonstring，如下所示

{"coaList":[{"iD":324,"strName":"Cash","hasChildren":false,"amount":3500.0,"transDate":1421346600000},{"iD":326,"strName":"Cash","hasChildren":false,"amount":2000.0,"transDate":1421346600000},{"iD":328,"strName":"HDFC Bank","hasChildren":false,"amount":2500.0,"transDate":1421346600000}]}

我需要将此字符串转换为CoaAccountList类对象.Below是CoaAccountList类。 CoaAccountList.java：

public class CoaAccountList implements Serializable  {

private List<COAAccount> coaList;

public List<COAAccount> getCoaList() {
    return coaList;
}

public void setCoaList(List<COAAccount> coaList) {
    this.coaList = coaList;
}

}

其中COAAccount类包含transDate作为TimeStamp变量，而在json字符串中它作为Long变量，所以我的转换过程为这个长transDate值产生com.google.gson.JsonSyntaxException。下面是我用来转换json字符串的代码到CoaAccountList

Gson gson = new Gson();
CoaAccountList transHisList=gson.fromJson(jsonString, CoaAccountList.class);

以下是COAAccount类。

COAAccount.java：

public class COAAccount implements Serializable {
private int iD;
private String strName;
private boolean hasChildren;
private float amount;
private Timestamp transDate;

public COAAccount() {
    super();
    // TODO Auto-generated constructor stub
}

public COAAccount(int iD, String strName, boolean hasChildren, float amount, Timestamp transDate) {
    super();
    this.iD = iD;
    this.strName = strName;
    this.hasChildren = hasChildren;
    this.amount = amount;
    this.transDate = transDate;
}

public int getiD() {
    return iD;
}

public void setiD(int iD) {
    this.iD = iD;
}

public String getStrName() {
    return strName;
}

public void setStrName(String strName) {
    this.strName = strName;
}

public boolean isHasChildren() {
    return hasChildren;
}

public void setHasChildren(boolean hasChildren) {
    this.hasChildren = hasChildren;
}

public float getAmount() {
    return amount;
}

public void setAmount(float amount) {
    this.amount = amount;
}

public Timestamp getTransDate() {
    return transDate;
}

public void setTransDate(Timestamp transDate) {
    this.transDate = transDate;
}

@Override
public String toString() {
    return strName;
}
}

请帮我将这个json字符串转换为CoaAccountList对象。

Answer 1

在需要使用自定义反序列化模式的情况下，Gson允许您根据类型注册自己的反序列化代码。

为此，您首先需要在GsonBuilder中实例化Gson，而不是在以下代码中：

GsonBuilder gson = new GsonBuilder();

然后，在处理类型JsonDeserializer时，您需要将GsonBuilder个实例附加到Timestamp，如下所示：

gson.registerTypeAdapter(Timestamp.class, new GsonTimestampDeserializer());

注意：GsonTimestampDeserializer是我们在下面创建的自定义类，您可以在技术上将其命名为任意内容。

注册自定义反序列化器时，当需要将原始类型（int，string，double等）转换为指定的注册类型时，Gson将根据需要自动从JsonDeserializer接口调用deserialize（）方法。为了利用这一点，我们实现了如下的解串器：

private class GsonTimestampDeserializer implements JsonDeserializer<Timestamp>{
    public Timestamp deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException{
        return new Timestamp(json.getAsJsonPrimitive().getAsLong());
    }
}

N.B：我假设您正在使用java.sql中的Timestamp对象，它提供了一个需要很长时间的构造函数。

全部放在一起：

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(Timestamp.class, new GsonTimestampDeserializer());

private class GsonTimestampDeserializer implements JsonDeserializer<Timestamp>{
    public Timestamp deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException{
        return new Timestamp(json.getAsLong());
    }
}

Gson gsonInstance = gson.create();

CoaAccountList transHisList = gsonInstance.fromJson(jsonString, CoaAccountList.class);

当Gson解析JSON字符串并尝试填写相应的值时，它会遇到transDate上的Timestamp类型，而不是使用java拥有的默认Object反序列化方案，使用我们提供的自定义反序列化方案来转换长到Timestamp对象。

这种方法可以推广到各种复杂的容器类，它们可以将数据存储为单一的基本类型，等效的GsonSerializer可以用来实现相反的。

Answer 2

您需要创建一个自定义反序列化方法来解析时间戳。

E.g。：

GsonBuilder builder = new GsonBuilder();

builder.registerTypeAdapter(Timestamp.class, new JsonDeserializer<Timestamp>() {

@Override
public Timestamp deserialize(JsonElement json, Type type, JsonDeserializationContext deserializationContext) throws JsonParseException {
    return new Timestamp(json.getAsJsonPrimitive().getAsLong());
    }
});

Gson gson = builder.create();
CoaAccountList transHisList = gson.fromJson(jsonString, CoaAccountList.class);

Answer 3

您需要在构建器中为Data.class注册Json反序列化程序。原始答案here

// Creates the json object which will manage the information received
    GsonBuilder builder = new GsonBuilder();

    // Register an adapter to manage the date types as long values
    builder.registerTypeAdapter(Date.class, new JsonDeserializer<Date>() {
        public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            return new Date(json.getAsJsonPrimitive().getAsLong());
        }
    });

如何使用时间戳数据反序列化包含arraylist的类

3 个答案: