I can't seem to find a concrete example of how to write a custom converter for Restlet. I'm having an issue with an object containing an ArrayList of a base type. (ie List )
I've been able to painstakingly do the conversion by reading in the object as JSON, converting it to a JSONObject and processing each field individually to create the representation I need on the deserialization. This seems very odd that I'd have to do this.
any help would be appreciated.
Related
I have json array & want to group weeks according to person id's as mentioned in below example. I tried code but unable to get it because i am new to free-marker code. The JSON Array as follows:-
[{"Hours":"5.500","Status":"Draft","Week":"17","person_name":"Raj","person_id":"1414"},
{"Hours":"0.500","Status":"Draft","Week":"17","person_name":"Raj","person_id":"1414"},
{"Hours":"24.500","Status":"Draft","Week":"14","person_name":"Mukesh","person_id":"1046"},
{"Hours":"7.500","Status":"Draft","Week":"15","person_name":"Mukesh","person_id":"1046"},
{"Hours":"3.000","Status":"Draft","Week":"16","person_name":"Mukesh","person_id":"1046"}]
Could please help me. The output in below foramt
for id {1046:[14,15,16], 1414:[17,17]}
Such kind of restructuring is not something that should be done inside a template. While FTL can add together map-like values and also list-like values, it would be very inefficient to hack this together with that (it's only for very simple tasks). The entries should be already grouped before passing the data to the template.
If you must initiate this from the template, then you will need a utility Java object that has a method that does this grouping, or a TemplateMethodModelEx implementation that does it. Then you call that utility object from the template (like utils.groupByPersonId(foo) or groupByPersonId(foo)). Such utility objects can be exposed to the template on various ways: as part of the data-model, globally as "shared variable" through the freemarker.tempalte.Configuration object, or by ensuring that the utility TemplateMethodModelEx (or any other TemplateModel) class is visible for Java and then do something like <#assign groupByPersonId = 'com.example.GroupByPersonIdMethod'?new()> in the template.
I'm guessing that the type is used for CRUD operations. Is it used for anything else besides that? I'm wondering what impact there could be from configuring how it gets populated.
The _class field is written to allow polymorphic properties in your domain model. See this sample:
class Wrapper {
Object inner;
}
Wrapper wrapper = new Wrapper();
wrapper.inner = new Foo();
couchbaseOperations.save(wrapper);
You see how the field inner will get Foo serialized and persisted. On the reading side of things we now have to find out which type to create an object of and the type information in Wrapper is not enough to do so as it only states Object.
That's why Spring Data object mapping persists an additional field (name customizable but defaulting to _class) to store that information to be able to inspect the source document, derive a type from the value written for that field and eventually map that document back to that particular type.
The Spring Data Couchbase reference documentation doesn't really document it, you can find information about the way this works in the docs for the MongoDB module. I've also created a ticket for Spring Data Couchbase to improve on the docs for that.
I am working on a REST service which uses Spring 4.x. As per a requirement I have to produce several different views out of same object. Sample URIs:
To get full details of a location service: /services/locations/{id}/?q=view:full
To get summary of a location service: /services/locations/{id}/?q=view:summary
I have thought of two solutions for such problem:
1. Create different objects for different views.
2. Create same object, but filter out the fields based on some configuration (shown below)
location_summary_fields = field1, field2
location_detail_fields = field1, field2, field3
Could someone help me to understand what could be an ideal solution? I am not aware of any standard practice followed for this kind of problems.
Thanks,
NN
In my opinion the best option is to use separate POJOs for different views. It's a lot easier to document it (for example when you use some automated tools like Swagger). Also you've to remember that your application will change after some time, and then having one common POJO could make troubles - then you'll need to add one field to one service and don't expose it through another.
See this article on how google gson uses annotations to convert a Java Object representation to a json format : http://www.javacreed.com/gson-annotations-example/
Since you want two different representations for the same object you could roll your own
toJson method as follows :
a) Annotate each field of you model with either #Summary, #Detail or #All
b) Implement a toJson() method that returns a json representation by examining the annotations for the fields and appropriately using them
If you need an XML representation same thing, except you would have a toXML().
I would need some clarification regarding the difference between Spring MVC formatters and converters.
My understanding of the main difference between them is that the formatter works on data that is going to be displayed to the end user such as a date, SSN or credit card number whereas the converter works on data hidden behind form controls such as the value attribute of an select's option.
Am I right or wrong? Can someone please provide advice and/or samples in order to better explain the difference between the two.
Converters are used to convert one Java type to another Java type. For example, from Long to java.util.Date or from Integer to Color or from String to Date. It can be used in the web tier or any other tier that needs conversion service.
Formatters are used to convert String to another Java type and back. So, one type must be String. You cannot, for example, write a formatter that converts a Long to a Date. Examples of formatters are DateFormatter, for parsing String to java.util.Date and formatting a Date. In addition, formatters' messages can be localized.
Conclusion: formatters are suitable in the web environment, such as a Spring MVC application.
Converter components are used for converting one type to another type and also to provide a cleaner separation by forcing to place all such conversion related code in one single place.
Spring already supports built-in converters for the commonly used types and the framework is extensible enough for writing custom converters as well.
Spring Formatters come into picture to format the data according to the display where it is rendered. Examples may include formatting date/timestamp values according to locales etc.
I am currently designing a solution to a problem I have. I need to dynamically generate an XML file on the fly using Java objects, in the same way JAXB generates Java classes from XML files, however the opposite direction. Is there something out there already like this?
Alternatively, a way in which one could 'save' a state of java classes.
The goal I am working towards is a dynamically changing GUI, where a user can redesign their GUI in the same way you can with iGoogle.
You already have the answer. It's JAXB! You can annotate your classes and then have JAXB marshal them to XML (and back) without the need to create an XML schema first.
Look at https://jaxb.dev.java.net/tutorial/section_6_1-JAXB-Annotations.html#JAXB%20Annotations to get started.
I don't know, if this is exactly what you're looking for, but there's the java.beans.XMLEncoder:
XMLEncoder enc = new XMLEncoder(new FileOutputStream(file));
enc.writeObject(obj);
enc.close();
The result can then be loaded by XMLDecoder:
XMLDecoder dec = new XMLDecoder(new FileInputStream(file));
Object obj = dec.readObject();
dec.close();
"generate xml from java objects:"
try xtream.
Here's what is said on the tin:
No mappings required. Most objects can be serialized without need for specifying mappings.
Requires no modifications to objects.
Full object graph support
For saving java object state:
Serialization is the way to do this in Java