I have this query
http://localhost:8555/list/csv?search={}
Where search is a json object (omitted other params as they are irrelevant here).
How can i convert this into a nested object?
public record CsvParams<T>(
T search,
/* Other query params */ ) {}
Right now im getting error that string cannot be cast into object.
class java.lang.String cannot be cast to class classname
Is there anyway to do this? Old solution uses ObjectMapper to convert string into corresbonding object. I was hoping that maybe there is a way to do it more simpli and remove this boilerplate.
Any single value of a query param can't be automatically converted to a non-primitive type. You can convert multiple params to a class, but not one that happens to be a JSON AFAIK. But you can create a converter custom deserialiser and then use it in different controllers, but in the end you'd still use an ObjectMapper.
More info on how to do the latter here: https://www.baeldung.com/spring-mvc-send-json-parameters
If you have to work with query params than I don't think you can have it converted automatically by Spring boot. But if you work with POST or PUT methods and can pass your params as request params in request body your JSON params can be automatically converted to class instances by Spring boot and no effort required from you. However, if you have to work with query param (say you have to use method GET so you have no request body) than you can use Json-Jackson library or Gson library to parse your Json into class instance. If you use Jackson you will need to use class ObjectMapper. For Jackson lib info see this site, for ObjectMapper class see Javadoc here. However, I wrote my own JsonUtils that is very good for simple usecases like yours. It allows to to parse simple JSON into a class with a single method. It is very simple and strait forward. It is a thin wrapper over Jackson library. See the Javadoc for method readObjectFromJsonString. Class JsonUtils is part of Open Source MgntUtils library. You can get it as Maven artifact on Maven Central and as a jar (with source code and Javadoc) on Github
I would like to use JAXB to read and write only a few parts of a very large XML. I would like to be able to do this without having to define a root object class for every element and attribute in the XML. The example below outlines what I need:
I have the XML
<A>
<B/>
<C/>
<D/>
</A>
I would like to use JAXB to get two functions
public String getC() {
...
return C
}
public void writeC(String C) {
... // replaces C value with the paramter C inside the XML
}
Without having to define a new class A with the annotations for B, C, and D.
How can I do this with JAXB? Is there a faster / more efficient way to achieve what I am trying to do than JAXB or a simple File Reader and Writer?
The purpose of this is to use a GUI to load and edit config settings that are stored in an XML file. Thank you.
I managed to solve this by using StAX instead. It offered complete flexibility for me to pick out which tags and which attrbitues I needed.
There is a project called EclipseLink MOXy that could solve this type of problem using JAXB. It allows you to map an existing java bean to or from xml and define exceptions from default JAXB using xml or json for the mapping description.
I am planning to provide a interface to iOS Apps, the developer asked to add an additional field call class contains the name of the pojo I used on server so he can convert to his class on client easily. The problem is I have to do this when the json lib is processing the values.I think the registerJsonValueProcessor can do the trick. I got then class name by obj.getClass().getName() but I still have no idea how to attach it to json-lib.
If you are using jackson for serialization/deserialization of json than please apply the annotation JsonTypeInfo on your class. It could help you
#JsonTypeInfo(use=Id.CLASS, include=As.PROPERTY, property="class")
I am trying to work out how to unmarshall and XML document to a Java document.
The top of the xml document looks like this
<xs:myData xmlns:xs="http://www.example.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.com example.xsd ">
There is a schema file whose top section looks like this:
<schema targetNamespace="http://www.example.com"
elementFormDefault="qualified"
xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:xs="http://www.example.com">
I would like to unmarshall the xml document using Spring/JaxB and eventually convert it to a JPA object. I am not sure how to go about so i looked for examples on google and came up with this http://thoughtforge.net/610/marshalling-xml-with-spring-ws-and-jaxb/
I understand most of it except how or where the schema is used.
I have seen other examples where the schema is explicitly specified, i.e.
SchemaFactory schemaFac = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema sysConfigSchema = schemaFac.newSchema(
new File("example.xsd"));
unmarshaller.setSchema(sysConfigSchema);
RootElement root = (RootElement)unmarshaller.unmarshal(
new File("example1.xml"));
How is the schema shown in the first link used to validate the xml document?
Are there any disadvantages to using Spring's jaxb2Marshaller as opposed to direct use of JAXB?
What is the effect of having the namespace next to the XmlElement annotation? (See the Person class)
I would appreciate any more examples showing Spring/REST with unmarshalling with schema validation.
Thanks
As far as I know JAXB does not parse xsi attribute to dereference XSD, load it and use for validation. Perhaps that was done to disable automatic validation, otherwise it would be problematic to switch it off :)
Spring Jaxb2Marshaller was obviously added to implement the same interface org.springframework.oxm.Marshaller (which is implemented also by CastorMarshaller, JibxMarshaller, ...). It is very powerful and allows you to tune JAXBContext in very flexible way (I can't imagine the scenario when provided API is not enough). From pattern point of new Jaxb2Marshaller is a builder, so it does not add anything to core JAXB functionality. But there are some evident advantages. For example, schema loading is very simple. In the article the Spring context refers the person.xsd (<property name="schema" value="classpath:schema/person.xsd"/>) which one need to put into resources explicitly. Then JAXB marshaller/unmarshaller will use this schema to validate XML when XML is generated/loaded.
#XmlElement(..., namepsace="xxx") will automatically generate this XML element with a specified namespace. It's rare case if somebody does not use namespaces. I would say writing XSD without namespaces is not normal, as you want to avoid the element name collision.
Using JAXB with RestTemplate is very simple. You need to be sure that JAXB runtime is in your classpath (JDK 6 already has it) and your bean is annotated with #XmlRootElement. Then just use Person person = restTemplate.getForObject(restServiceUrl, Person.class),
In Jersey RESTful frame work, I know I can get xml data in client as following:
private static final String BaseURI = "http://DOMAN.com";
ClientConfig config = new DefaultClientConfig();
Client client = Client.create(config);
WebResource service = client.resource(BaseURI);
String xmlData = service.path("rest").path("todos").accept(
MediaType.APPLICATION_XML).get(String.class)
My question is how can I parse the xmlData then? I would like to get the needed data from xmlData, and transfer the needed data to JSON, what is the best way to implement this?
As a general rule, NEVER convert straight from XML to JSON (or vice versa) if you do not have to.
Rather, bind data from XML or JSON to POJOs, then do the other conversion. While it may seem non-intuitive this results in cleaner result and less problems, since conversions between POJOs and data formats have much more options, mature, well-designed libs; and POJOs are easier to configure (with annotations) and have more metadata to guide conversion process.
Direct conversions libs (like Jettison, see below) are plagued with various issues; often producing "franken-JSON", JSON that is technically correct but looks alien because of added constructs needed by conversion.
In case of Jersey, then, use JAXB for XML to/from POJOs, and Jackson for doing the same with JSON. These are libraries Jersey uses anyway; and direct usage is quite easy.
If you absolutely insist on direct conversion, you could try Jettison, but be prepared to hit a problem with Lists, arrays and Maps, if you need them (esp. single-element arrays -- arrays are problematic with XML, and auto-conversion often goes wrong).
If your service doesn't provide JSON as an option already (what happens if you change MediaType.APPLICATION_XML to MediaType.APPLICATION_JSON?), then I believe you have a few options, which I list in order of my preference.
Option 1: You have an XML schema for the the data
If you have an XML schema for the returned XML, you could use xjc to generate the JAXB annotated java classes and then leverage jackson to convert the instances to JSON data. I think this will get you going fast by leveraging this libraries over doing the parsing youself. Jackson is a robust library, used by glassfish for their Jersey(JAX-RS) implementation and I don't feel there is any risk in depending on this library.
Option 2: Use the json.org library, but I've had significant problem with this library having to do with its reflection-based methodology, etc. That said, it might work well for you...and you can test relatively easily and see if it does meet your requirements. If so...you're done! =)
Option 3: You don't have the XML schema and/or you want more control
as #Falcon pointed out, you can always use traditional XML parsing technologies to parse the XML into whatever you want. I'm partial to SAX parsing, but DOM could work depending on xml side
Regards,
Steve
Simplest and easiest way would be using org.json package : http://json.org/javadoc/org/json/XML.html
XML.toJSONObject(xmlData).toString()
Just this one line apart from necessary import statement will do it all.
Now that i have mentioned org.json library, lot of people may comment bad about it. Remember, I have said the simplest and easiest way, not the best or the most performant way ;-)
In case you are using maven, add this dependency :
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20090211</version>
</dependency>
Do you have any access to the "lower level interface" that generates the XML? If you do, the only change needed is to have the xml objects annotated with "#XmlRootElement". Then, you can just pass back the XMLobject as JSON without any further code.
Check Jsonix. If you have an XML schema, you can generate XML-JSON mappings and unmarshal/marshal XML in JavaScript. Very similar to JAXB (which Steve Siebert mentioned), but works on client.
// The PO variable provides Jsonix mappings for the purchase order test case
// Its definition will be shown in the next section
var PO = { };
// ... Declaration of Jsonix mappings for the purchase order schema ...
// First we construct a Jsonix context - a factory for unmarshaller (parser)
// and marshaller (serializer)
var context = new Jsonix.Context([ PO ]);
// Then we create an unmarshaller
var unmarshaller = context.createUnmarshaller();
// Unmarshal an object from the XML retrieved from the URL
unmarshaller.unmarshalURL('/org/hisrc/jsonix/samples/po/test/po-0.xml',
// This callback function will be provided with the result
// of the unmarshalling
function(result) {
// We just check that we get the values we expect
assertEquals('Alice Smith', result.value.shipTo.name);
assertEquals('Baby Monitor', result.value.item[1].productName);
});