Java 对接口类型使用Gson
我正在编写一些服务器代码,其中客户端以JSON的形式发送请求。我的问题是,有许多可能的请求,在小的实现细节上都有所不同。 因此,我考虑使用一个请求接口,定义如下:Java 对接口类型使用Gson,java,json,gson,Java,Json,Gson,我正在编写一些服务器代码,其中客户端以JSON的形式发送请求。我的问题是,有许多可能的请求,在小的实现细节上都有所不同。 因此,我考虑使用一个请求接口,定义如下: public interface Request { Response process ( ); } 在此基础上,我在名为LoginRequest的类中实现了接口,如图所示: public class LoginRequest implements Request { private String type = "L
public interface Request {
Response process ( );
}
在此基础上,我在名为LoginRequest
的类中实现了接口,如图所示:
public class LoginRequest implements Request {
private String type = "LOGIN";
private String username;
private String password;
public LoginRequest(String username, String password) {
this.username = username;
this.password = password;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
/**
* This method is what actually runs the login process, returning an
* appropriate response depending on the outcome of the process.
*/
@Override
public Response process() {
// TODO: Authenticate the user - Does username/password combo exist
// TODO: If the user details are ok, create the Player and add to list of available players
// TODO: Return a response indicating success or failure of the authentication
return null;
}
@Override
public String toString() {
return "LoginRequest [type=" + type + ", username=" + username
+ ", password=" + password + "]";
}
}
public class LoginRequestCreator implements InstanceCreator<LoginRequest> {
@Override
public LoginRequest createInstance(Type arg0) {
return new LoginRequest("username", "password");
}
}
为了使用JSON,我创建了一个GsonBuilder
实例,并注册了一个InstanceCreator
,如图所示:
public class LoginRequest implements Request {
private String type = "LOGIN";
private String username;
private String password;
public LoginRequest(String username, String password) {
this.username = username;
this.password = password;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
/**
* This method is what actually runs the login process, returning an
* appropriate response depending on the outcome of the process.
*/
@Override
public Response process() {
// TODO: Authenticate the user - Does username/password combo exist
// TODO: If the user details are ok, create the Player and add to list of available players
// TODO: Return a response indicating success or failure of the authentication
return null;
}
@Override
public String toString() {
return "LoginRequest [type=" + type + ", username=" + username
+ ", password=" + password + "]";
}
}
public class LoginRequestCreator implements InstanceCreator<LoginRequest> {
@Override
public LoginRequest createInstance(Type arg0) {
return new LoginRequest("username", "password");
}
}
我得到了预期的输出
我希望做的事情是替换行Request=parser.fromJson(completeInput,LoginRequest.class)代码>类似于Request-Request=parser.fromJson(completeInput,Request.class)代码>但这样做不起作用,因为请求
是一个接口
我希望我的Gson
根据收到的JSON返回适当类型的请求
我传递给服务器的JSON示例如下所示:
{
"type":"LOGIN",
"username":"someuser",
"password":"somepass"
}
重申一下,我正在寻找一种方法来解析来自客户端的请求(JSON),并返回实现请求
接口的类的对象。默认情况下,GSON无法区分序列化为JSON的类;换句话说,您需要显式地告诉解析器您期望的是什么类
解决方案可以是自定义反序列化或使用类型适配器,如前所述。所述类型的多态映射在没有某种自定义编码的Gson中不可用。有一个扩展类型适配器提供了您正在寻找的大部分功能,但需要注意的是,多态子类型需要提前声明给适配器。以下是其使用示例:
public interface Response {}
public interface Request {
public Response process();
}
public class LoginRequest implements Request {
private String userName;
private String password;
// Constructors, getters/setters, overrides
}
public class PingRequest implements Request {
private String host;
private Integer attempts;
// Constructors, getters/setters, overrides
}
public class RequestTest {
@Test
public void testPolymorphicSerializeDeserializeWithGSON() throws Exception {
final TypeToken<List<Request>> requestListTypeToken = new TypeToken<List<Request>>() {
};
final RuntimeTypeAdapterFactory<Request> typeFactory = RuntimeTypeAdapterFactory
.of(Request.class, "type")
.registerSubtype(LoginRequest.class)
.registerSubtype(PingRequest.class);
final Gson gson = new GsonBuilder().registerTypeAdapterFactory(
typeFactory).create();
final List<Request> requestList = Arrays.asList(new LoginRequest(
"bob.villa", "passw0rd"), new LoginRequest("nantucket.jones",
"crabdip"), new PingRequest("example.com", 5));
final String serialized = gson.toJson(requestList,
requestListTypeToken.getType());
System.out.println("Original List: " + requestList);
System.out.println("Serialized JSON: " + serialized);
final List<Request> deserializedRequestList = gson.fromJson(serialized,
requestListTypeToken.getType());
System.out.println("Deserialized list: " + deserializedRequestList);
}
}
公共接口响应{}
公共接口请求{
公众反应过程();
}
公共类LoginRequest实现请求{
私有字符串用户名;
私有字符串密码;
//构造函数、getter/setter、重写
}
公共类PingRequest实现请求{
私有字符串主机;
私有整数尝试;
//构造函数、getter/setter、重写
}
公共类请求测试{
@试验
public void testPolymorphicSerializeDeserializeWithGSON()引发异常{
final TypeToken requestListTypeToken=新的TypeToken(){
};
最终RuntimeTypeAdapterFactory类型工厂=RuntimeTypeAdapterFactory
.of(Request.class,“type”)
.registerSubtype(LoginRequest.class)
.registerSubtype(PingRequest.class);
final Gson Gson=new GsonBuilder().registerTypeAdapterFactory(
创建();
最终列表requestList=Arrays.asList(新登录请求(
“bob.villa”、“passw0rd”、新登录请求(“nantucket.jones”,
“crabdip”),新的PingRequest(“example.com”,5));
序列化的最终字符串=gson.toJson(requestList,
requestListTypeToken.getType());
System.out.println(“原始列表:“+requestList”);
System.out.println(“序列化JSON:+Serialized”);
最终列表反序列化dRequestList=gson.fromJson(序列化,
requestListTypeToken.getType());
System.out.println(“反序列化列表:“+deserializedRequestList”);
}
}
请注意,您实际上不需要在单个Java对象上定义type
属性-它只存在于JSON中。库默认提供对多态类型的支持。以下是它的工作原理:
// tell genson to enable polymorphic types support
Genson genson = new Genson.Builder().setWithClassMetadata(true).create();
// json value will be {"@class":"mypackage.LoginRequest", ... other properties ...}
String json = genson.serialize(someRequest);
// the value of @class property will be used to detect that the concrete type is LoginRequest
Request request = genson.deserialize(json, Request.class);
您还可以为您的类型使用别名
// a better way to achieve the same thing would be to use an alias
// no need to use setWithClassMetadata(true) as when you add an alias Genson
// will automatically enable the class metadata mechanism
genson = new Genson.Builder().addAlias("loginRequest", LoginRequest.class).create();
// output is {"@class":"loginRequest", ... other properties ...}
genson.serialize(someRequest);
假设您可能拥有的不同JSON请求彼此之间没有太大差异,我建议使用不同的方法,我认为更简单
假设您有以下3个不同的JSON请求:
{
"type":"LOGIN",
"username":"someuser",
"password":"somepass"
}
////////////////////////////////
{
"type":"SOMEREQUEST",
"param1":"someValue",
"param2":"someValue"
}
////////////////////////////////
{
"type":"OTHERREQUEST",
"param3":"someValue"
}
Gson允许您使用单个类来包装所有可能的响应,如下所示:
public class Request {
@SerializedName("type")
private String type;
@SerializedName("username")
private String username;
@SerializedName("password")
private String password;
@SerializedName("param1")
private String param1;
@SerializedName("param2")
private String param2;
@SerializedName("param3")
private String param3;
//getters & setters
}
Gson gson = new Gson();
Request request = gson.fromJson(jsonString, Request.class);
通过使用注释@SerializedName
,当Gson尝试解析JSON请求时,它只需查找类中每个命名属性的JSON请求中是否有同名字段。如果没有这样的字段,则类中的属性仅设置为null
通过这种方式,您可以仅使用请求
类解析许多不同的JSON响应,如下所示:
public class Request {
@SerializedName("type")
private String type;
@SerializedName("username")
private String username;
@SerializedName("password")
private String password;
@SerializedName("param1")
private String param1;
@SerializedName("param2")
private String param2;
@SerializedName("param3")
private String param3;
//getters & setters
}
Gson gson = new Gson();
Request request = gson.fromJson(jsonString, Request.class);
一旦将JSON请求解析到类中,就可以将数据从wrap类传输到具体的XxxxRequest
对象,类似于:
switch (request.getType()) {
case "LOGIN":
LoginRequest req = new LoginRequest(request.getUsername(), request.getPassword());
break;
case "SOMEREQUEST":
SomeRequest req = new SomeRequest(request.getParam1(), request.getParam2());
break;
case "OTHERREQUEST":
OtherRequest req = new OtherRequest(request.getParam3());
break;
}
请注意,如果您有许多不同的JSON请求,并且这些请求彼此非常不同,那么这种方法会变得有点乏味,但即便如此,我认为这是一个很好且非常简单的方法…我找到了这个答案:它解决了我在使用Calendar作为接口时的问题,因为运行时类型将是GregorianCalendar。有一个实用方法为泛型接口创建GSON
//注册接口的实用方法及其在GSON中的实现
public static <T> Gson buildInterface(Class<T> interfaceType, List<Class<? extends T>> interfaceImplmentations) {
final RuntimeTypeAdapterFactory<T> typeFactory = RuntimeTypeAdapterFactory.of(interfaceType, "type");
for (Class<? extends T> implementation : interfaceImplmentations) {
typeFactory.registerSubtype(implementation);
}
final Gson gson = new GsonBuilder().registerTypeAdapterFactory(typeFactory).create();
return gson;
}
公共静态Gson构建接口(Class interfaceType,List您可以提供其他您可以从服务器获得的不同JSON响应的示例吗?因为如果您没有太多和非常不同的可能性,有一些事情您可以轻松完成…感谢@MiKO的输入。其他可能的请求有PlayRequest
,LogoutRequest
,GetPlayersRequest
,JoinGameRequest
,StartGameRequest
等等……我的意思是,如果您可以为至少一种其他类型的请求提供JSON请求的示例。我的意思是,对于您的LoginRequest
,您有五个字段:类型
,用户名
和密码
,其他请求如何它们看起来像吗?谢谢@MikO。我猜开关盒结构可能会进入某种请求工厂。谢谢。那就好了