Gson parsing an exception to an empty string _java

Objective

In the actual development project, the server often uses the empty string "" as the return result indicates the null value, but this will encounter the problem in the Gson, if this data type is not the string, Gson parsing will be the error

JSON exception condition

Let's look at a background-returned JSON

Under normal conditions JSON:

{"
 code": 0,
 "msg": "OK",
 "data": {
  "id": 5638,
  "newsId": 5638
 }
}

The entity class corresponding to the data section:

public class Jsonbean {
 private int id;
 private int newsId;

 public int getId () {return
  ID;
 }

 public void setId (int id) {
  this.id = ID;
 }

 public int Getnewsid () {return
  newsId;
 }

 public void Setnewsid (int newsId) {
  this.newsid = newsId;
 }
}

exception Condition JSON (The Background Database NewSID field is not queried for the corresponding data):

{"
 code": 0,
 "msg": "OK",
 "data": {
  "id": 5638,
  "newsId": ""
 }
}

So Gson throws a parse error exception when parsing, and the app crashes because it can't convert "" to int

Processing of JSON exceptions

We expect the JSON exception returned in the background to parse successfully, and the null value will be converted to the default value, such as:newsId=0;

This eliminates the background developer output when you do corrective, or to rely on their own ah---

We write a type converter for int value, we need to implement Gson JsonSerializer<T> interface and JsonDeserializer<T> , that is, serialization and deserialization interface

public class Integerdefault0adapter implements Jsonserializer<integer>, jsondeserializer<integer> {
 @Override Public
 Integer Deserialize (jsonelement json, Type Typeoft, Jsondeserializationcontext context)
   Throws Jsonparseexception {
  try {
   if (json.getasstring). Equals ("") | | Json.getasstring (). Equals ("null")) {//defined as int type, if background returns "" or null, returns 0 return
    0;
   }
  catch (Exception Ignore) {
  }
  try {return
   json.getasint ();
  } catch (NumberFormatException e) {
   throw new Jsonsyntaxexception (e);
  }

 @Override public
 jsonelement Serialize (Integer src, Type typeofsrc, Jsonserializationcontext context) {
  return new jsonprimitive (SRC);
 }

Same long and double type

Double=>

public class Doubledefault0adapter implements Jsonserializer<double>, jsondeserializer<double> {
 @ Override Public
 Double Deserialize (jsonelement json, Type Typeoft, Jsondeserializationcontext context) throws jsonparseexception {
  try {
   if (json.getasstring). Equals ("") | | Json.getasstring (). Equals ("null")) {//defined as the double type, if the background returns "" or NULL, returns 0.00 return
    0.00;
  }
   catch ( Exception ignore) {
  }
  try {return
   json.getasdouble ();
  } catch (NumberFormatException e) {
   throw new Jsonsyntaxexception (e);
  }
 }

 @Override public
 jsonelement Serialize (Double src, Type typeofsrc, Jsonserializationcontext context) {
  return new jsonprimitive (SRC);
 }

Long=>

public class Longdefault0adapter implements Jsonserializer<long>, jsondeserializer<long> {
 @Override Public
 Long Deserialize (jsonelement json, Type Typeoft, Jsondeserializationcontext context)
  throws jsonparseexception {
  try {
   if (json.getasstring). Equals ("") | | Json.getasstring (). Equals ("null")) {//defined as a long and if the background returns "" or null, returns 0 return
     0l;
    }
   catch (Exception Ignore) {
  }
  try {return
   json.getaslong ();
  } catch (NumberFormatException e) {
   throw new Jsonsyntaxexception (e);
  }

 @Override public
 jsonelement Serialize (Long src, Type typeofsrc, Jsonserializationcontext context) {
  return New Jsonprimitive (SRC);
 }
}

So the use is this:

return new Retrofit.builder ()
  . Client (okhttpclient)/Set the network Access Framework
  . Addconverterfactory ( Gsonconverterfactory.create (Buildgson ())//Add JSON Transformation Framework
  . Addcalladapterfactory ( Rxjavacalladapterfactory.create ())//Let retrofit support Rxjava
  . BaseURL (BaseURL)
  . Build ();

/**
 * Increase background return "" and "null" processing
 * 1.int=>0 *
 2.double=>0.00
 * 3.long=>0l
 * * @return
 */Public
static Gson Buildgson () {
 if (Gson = null) {
  Gson = new Gsonbuilder ()
    . Registertypea Dapter (Integer.class, New Integerdefault0adapter ())
    . Registertypeadapter (Int.class, new Integerdefault0adapter ())
    . Registertypeadapter (Double.class, New Doubledefault0adapter ())
    . Registertypeadapter (Double.class, New Doubledefault0adapter ())
    . Registertypeadapter (Long.class, new Longdefault0adapter ())
    . Registertypeadapter (Long.class, New Longdefault0adapter ())
    . Create ();
 return Gson;
}

It's never going to crash because the background JSON field is empty.

Summarize

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