I would like to set the value of a field which is of the type map using the reflection api for a protobuf message.
I have tried using the set field method as shown below. This does not seem to work. I can make it work by using the suggestion in Filling up a map field in Proto using reflection API. But this not seem to be a nice solution!
message OuterMessage {
map<string, InnerMessage> mapInner = 1;
}
Map<String, InnerMessage> map = new HashMap<>();
map.put("R1", im1);
map.put("R2", im2);
OuterMessage.newBuilder().setField(fieldDescriptor, map);
I am getting the error,
java.lang.ClassCastException: java.base/java.util.HashMap cannot be cast to java.base/java.util.List
Which is understandable when i look at the implementation. But how else would i set a map?
Related
I'm deserializing a large XML file (not mine) and it contains custom entities defined as:
<!ENTITY math "mathematics">
and elements used this way:
<field>&math;</field>
When I try to deserialize it by:
XmlMapper xmlMapper = new XmlMapper();
ClassLoader classloader = Thread.currentThread().getContextClassLoader();
return xmlMapper.readValue(classloader.getResourceAsStream("file.xml"), MyClass.class);
I get this error:
com.fasterxml.jackson.databind.JsonMappingException: Undeclared general entity "math"
I think it might be a security measure to prevent Xml External Entity injections.
Is there a way to mark these custom entities as valid? Like create an Enum for them or something?
If not, is there a flag to just parse these as Strings?
Update:
I was able to work around this problem by basically doing a find-replace on the text file. It's quite an ugly solution and if anyone has a better idea, I'm all ears. :)
I know it may be a little late, but just in case someone else is stuck on the same issue:
You have to set a custom XMLResolver as XMLInputFactory's property:
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import com.ctc.wstx.api.WstxInputProperties;
import javax.xml.stream.XMLResolver;
import javax.xml.stream.XMLStreamException;
var xmlMapper = new XmlMapper();
xmlMapper.getFactory().getXMLInputFactory().setProperty(
WstxInputProperties.P_UNDECLARED_ENTITY_RESOLVER,
new XMLResolver() {
#Override
public Object resolveEntity(String publicId, String systemId, String baseUri, String ns) throws XMLStreamException {
// replace the entity with a string of your choice, e.g.
switch (ns) {
case "nbsp":
return " ";
default:
return "";
}
// some useful tool is org.apache.commons.text.StringEscapeUtils
// e.g.
// return StringEscapeUtils.escapeXml10(StringEscapeUtils.unescapeHtml4('&' + ns + ';'));
}
}
);
// then xmlMapper.readValue....
It happens to me that I am bound to use light 4j .
I couldn't find a simple example of a simple CRUD service in entire source code base of light 4j.
All there examples simply return dummy response in their handler.
None of them have actually injected a service and perform any logic .
Q1) Is anyone aware of any documentation or sample source code of light 4j which is complete in terms of CRUD operation including how to inject services with multiple implementation ?
PS : There documentation just display how to get ALL the implementations of a Service and not a SINGLE implementation out of many.
Q2) The actual question :
How to convert a very simple JSON Request body to a JAVA POJO object .
The worst of all possibility I found out is this .
Map<String, Object> bodyMap = (Map<String, Object>) exchange
.getAttachment(BodyHandler.REQUEST_BODY);
AccontRegisterRequest request = new AccontRegisterRequest();
request.setDob(LocalDate.parse((String) bodyMap.get("dob")));
request.setName((String) bodyMap.get("name"));
request.setInitialDeposite(
Float.parseFloat((String) bodyMap.get("initialDeposite")));
Request Payload
{
"name" : "Some Name",
"dob" : "1999-02-02",
"initialAmount" : 10000
}
Please dont recommend of adding a key in this JSON like this :
{
"somekey like body" : {
... and here goes by previous json
}
}
Because this BodyHandler is UN-NECESSARILY reading the input stream and converts it into a linkedHasMap.
So I cannot simply read the request input stream in my logic and pass it to JACKSON mapper to create my POJO.
Please help me to get me rid of this .
Sorry I didn't find this question in my previous scan.
You can convert a map to POJO with Jackson and it is very fast as there is no need to parse the JSON.
Take a look at this example in light-oauth2
https://github.com/networknt/light-oauth2/blob/master/client/src/main/java/com/networknt/oauth/client/handler/Oauth2ClientPostHandler.java#L44
I'm looking to create a gRPC response that returns a list of maps. Here is what I imagined the structure being:
message GetSettingsResponse {
repeated map<string, string> settings = 1;
}
Repeating maps is not supported, however, and I had to nest the map in a separate message to make it work:
message GetSettingsResponse {
repeated Setting settings = 1;
}
message Setting {
map<string, string> setting = 1;
}
This works, but it forces us to write some confusing code on both the client and server. Is there any way to avoid this solution and get closer to my desired structure?
No, basically. What you have is the closest you can do in protobuf.
I'd like to change the representation of C# Doubles to rounded Int64 with a four decimal place shift in the serialization C# Driver's stack for MongoDB. In other words, store (Double)29.99 as (Int64)299900
I'd like this to be transparent to my app. I've had a look at custom serializers but I don't want to override everything and then switch on the Type with fallback to the default, as that's a bit messy.
I can see that RegisterSerializer() won't let me add one for an existing type, and that BsonDefaultSerializationProvider has a static list of primitive serializers and it's marked as internal with private members so I can't easily subclass.
I can also see that it's possible to RepresentAs Int64 for Doubles, but this is a cast not a conversion. I need essentially a cast AND a conversion in both serialization directions.
I wish I could just give the default serializer a custom serializer to override one of it's own, but that would mean a dirty hack.
Am I missing a really easy way?
You can definitely do this, you just have to get the timing right. When the driver starts up there are no serializers registered. When it needs a serializer, it looks it up in the dictionary where it keeps track of the serializers it knows about (i.e. the ones that have been registered). Only it it can't find one in the dictionary does it start figuring out where to get one (including calling the serialization providers) and if it finds one it registers it.
The limitation in RegisterSerializer is there so that you can't replace an existing serializer that has already been used. But that doesn't mean you can't register your own if you do it early enough.
However, keep in mind that registering a serializer is a global operation, so if you register a custom serializer for double it will be used for all doubles, which could lead to unexpected results!
Anyway, you could write the custom serializer something like this:
public class CustomDoubleSerializer : BsonBaseSerializer
{
public override object Deserialize(BsonReader bsonReader, Type nominalType, Type actualType, IBsonSerializationOptions options)
{
var rep = bsonReader.ReadInt64();
return rep / 100.0;
}
public override void Serialize(BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
{
var rep = (long)((double)value * 100);
bsonWriter.WriteInt64(rep);
}
}
And register it like this:
BsonSerializer.RegisterSerializer(typeof(double), new CustomDoubleSerializer());
You could test it using the following class:
public class C
{
public int Id;
public double X;
}
and this code:
BsonSerializer.RegisterSerializer(typeof(double), new CustomDoubleSerializer());
var c = new C { Id = 1, X = 29.99 };
var json = c.ToJson();
Console.WriteLine(json);
var r = BsonSerializer.Deserialize<C>(json);
Console.WriteLine(r.X);
You can also use your own serialization provider to tell Mongo which serializer to use for certain types, which I ended up doing to mitigate some of the timing issues mentioned when trying to override existing serializers. Here's an example of a serialisation provider that overrides how to serialize decimals:
public class CustomSerializationProvider : IBsonSerializationProvider
{
public IBsonSerializer GetSerializer(Type type)
{
if (type == typeof(decimal)) return new DecimalSerializer(BsonType.Decimal128);
return null; // falls back to Mongo defaults
}
}
If you return null from your custom serialization provider, it will fall back to using Mongo's default serialization provider.
Once you've written your provider, you just need to register it:
BsonSerializer.RegisterSerializationProvider(new CustomSerializationProvider());
I looked through the latest iteration of the driver's code and checked if there's some sort of backdoor to set custom serializers. I am afraid there's none; you should open an issue in the project's bug tracker if you think this needs to be looked at for future iterations of the driver (https://jira.mongodb.org/).
Personally, I'd open a ticket -- and if a quick workaround is necessary or required, I'd subclass DoubleSerializer, implement the new behavior, and then use Reflection to inject it into either MongoDB.Bson.Serialization.Serializers.DoubleSerializer.__instance or MongoDB.Bson.Serialization.BsonDefaultSerializationProvider.__serializers.
I have an unmarshaller along with an MySchema.xsd file.
StreamSource sources = new StreamSource(getClass().getClassLoader().getResourceAsStream("/xmlValidation.xsd"));
SchemaFactory sf = SchemaFactory.newInstance( XMLConstants.W3C_XML_SCHEMA_NS_URI );
unmarshaller.setSchema(sf.newSchema(sources));
And make a call to unmarshaller.setEventHandler() function, to specify a custom validation event handler, which basically format a error tips string , by:
final String errorString = new String();
unmarshaller.setEventHandler(new ValidationEventHandler() {
#Override
public boolean handleEvent(ValidationEvent validationevent) {
if(validationevent.getSeverity()!= ValidationEvent.WARNING){
errorString.format( "Line:Col[" + validationevent.getLocator().getLineNumber()
+ ":" + validationevent.getLocator().getColumnNumber()
+ "]:" + validationevent.getMessage());
return false;
}
return true;
}
});
The above codes seem work ok(I can get java object when the input string is validated. and also the error tips string is formated as excepted)
The problem is that, when the input xml is not well form, it also throw a SaxParseException.
Thanks in advance.
Andrew
Well formed relates to the XML syntax itself, as opposed to being valid WRT an XML schema:
http://en.wikipedia.org/wiki/Well-formed_element
If you have XML that is not well formed then you will get a ValidationEvent.FATAL_ERROR and unmarshalling will not be able to continue, as the underlying parser used by JAXB cannot continue.
For more information:
http://bdoughan.blogspot.com/2010/12/jaxb-and-marshalunmarshal-schema.html
K, I mess up something and get this problem.
Now I figure it out. If I am wrong, please point me out. below it's what I find in javadoc and test on my project:
javax.xml.bind.ValidationEventHandler can handler the constrain error with the given schema constrains, when unmarshaller is unmarshaling.
unmarshaller.unmarshal(xmlInputStream);
The ValidationEventHandler will be called during the unmarshaling process if error occurs.
The SAXEception will be thrown, if the xmlInputStream is not well form.
And I cant find a way to catch the SAXException, throw by the sax parser, so I guess using validation during unmarshaling can't due with un-well form xml string.
I use javax.xml.validation.Validator to validate that the xml string is well form and under constrain.
jaxbValidator.validate(xmlSource);
The above code will throw SAXException.
If no exception is thrown, then unmarshall the xml string into object.