直接new 出來的Gson 物件是無法解析為""的Date屬性的.

需要通過GsonBuilder來進行建立.

static Gson ignoreDateGson=new GsonBuilder().registerTypeAdapterFactory(new DateNullAdapterFactory<>()).create();

這個registerTypeAdapterFactory()方法就是新增自己的介面卡,來對某些特定的型別進行處理.

new 出來的這個DateNullAdapterFactory.class 需要自己寫.

import java.util.Date;

import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;

public class DateNullAdapterFactory<T> implements TypeAdapterFactory {
	
    @SuppressWarnings("unchecked")
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        Class<T> rawType = (Class<T>) type.getRawType();
        if (rawType != Date.class) {
            return null;
        }
        return (TypeAdapter<T>) new DateNullAdapter();
    }
}
 

這個是為了指定什麼型別的屬性需要進行處理.真正處理的Date 的操作是在DateNullAdapter 裡面.

以下是這個類的程式碼.

import java.io.IOException;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.Date;
import java.util.Locale;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.internal.bind.DateTypeAdapter;
import com.google.gson.internal.bind.util.ISO8601Utils;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;
import com.zxtc.common.utils.StringUtils;

public class DateNullAdapter extends TypeAdapter<Date>{
	
	  public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
		    @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal
		    @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
		      return typeToken.getRawType() == Date.class ? (TypeAdapter<T>) new DateTypeAdapter() : null;
		    }
		  };

		  private final DateFormat enUsFormat
		      = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.US);
		  private final DateFormat localFormat
		      = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT);

		  @Override public Date read(JsonReader in) throws IOException {
			  
		    if (in.peek() == JsonToken.NULL) {
		      in.nextNull();
		      return null;
		    }
		    String jsonStr = in.nextString();
		    if(StringUtils.isBlank(jsonStr)) {
		    	return null;
		    }else {
		    	return deserializeToDate(jsonStr);
		    }
		  }

		  private synchronized Date deserializeToDate(String json) {
		    try {
		      return localFormat.parse(json);
		    } catch (ParseException ignored) {
		    }
		    try {
		      return enUsFormat.parse(json);
		    } catch (ParseException ignored) {
		    }
		    try {
		    	return ISO8601Utils.parse(json, new ParsePosition(0));
		    } catch (ParseException e) {
		      throw new JsonSyntaxException(json, e);
		    }
		  }

		  @Override public synchronized void write(JsonWriter out, Date value) throws IOException {
		    if (value == null) {
		      out.nullValue();
		      return;
		    }
		    String dateFormatAsString = enUsFormat.format(value);
		    out.value(dateFormatAsString);
		  }
		  
		  
}
 

接下來就可以進行反序列化了.

做一個例子:

import java.util.Date;

public class User {
	
	private String name;
	private Date birth;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Date getBirth() {
		return birth;
	}
	public void setBirth(Date birth) {
		this.birth = birth;
	}
}
 

對兩種gson建立方式進行對比.

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class Test {
	public static void main(String[] args) {
		Gson ignoreDateGson=new GsonBuilder().registerTypeAdapterFactory(new DateNullAdapterFactory<>()).create();
		Gson gson =new GsonBuilder().create();
		String  str = "{\"name\":\"張三\",\"birth\":\"\"}";
		User t1 = ignoreDateGson.fromJson(str, User.class);
//		User t2 = gson.fromJson(str, User.class);
		System.out.println(t1.getBirth());
		
	}
}

上邊的方法輸出為null,

下邊的方法直接報錯.