I have used Spring #ConfigurationProperties to map values from properties file to java object. It works flawlessly and I am trying to find the logic behind that,
I tried Java reflection packages to create proxy but it allows only interfaces. For classes I need to use third party library which I would like avoid at this point.
I explored the source in IDE as well as in Github but not able to get the
actual code.
Can anyone direct me in the right way to find the logic behind the #ConfigurationProperties and how it works?
Related
I have some classes having Java code with spring annotation, however its observed when we call them from .feature file, getting org.graalvm.polyglot.PolyglotException. When removed those annotation it worked. Now we have my libraries which use such classes, so can anybody help on same how to invoke spring flavoured classes from feature files.
Please note that re-using "production" objects in your test-suites is a common mistake, please don't do it. Because the risk is that when you re-factor some Java classes, you will never know if it really breaks some API consumers.
You can assume that what you are trying to do is not supported by Karate. If you follow this process, others will be in a better position to suggest a workaround: https://github.com/karatelabs/karate/wiki/How-to-Submit-an-Issue
I am trying to do something very similar to what spring #ConfigurationProperties does to map properties to a Java POJO, but at runtime. I am hoping to be able to reuse the spring framework code that does this for spring properties.
I looked through a bunch of spring's code but I am having trouble isolating the code that does this specific functionality. I can write my own algorithm to do this, but it feels like a waste since I know this is existing functionality in the spring framework and I have spring dependencies in my project already.
After some more digging, I found the following class: ConfigurationPropertiesBinder, which binds properties from various PropertySources to a Bindable object. I was able to extract enough information from this bean to create my own version to do the conversion I was looking for.
Suppose I've got a Java application, which uses properties files as its configuration. Now I'd like to make the application re-read the configuration without restart. I'll call such configuration "refreshable".
What is the easiest way to do that?
Suppose I am developing an application from scratch. How should I design it to make its configuration "refreshable"?
Using the commons-configuration is probably the easiest way to go. Here is an example of usage. There are many other features included, like hierarchical configuration (with overriding by defaults), JDBC sources, etc.
There must be some class say ConfigurationReader which has methods to read configurations and store them in-memory in some collection. Make sure that all the other classes uses the config information this in-memory map.
Now you can make a function call to re-read all the parameters and update the in-memory map, so that rest of the application will use the updated values from the map. This way you need to change code in entire application.
I am current using Seasar2 Framework on a project that I am in. The framework is quite popular here in Japan but I am having problem in finding English documentations. Even on their official English translation site, they just discuss that the framework use Dependency Injection and AOP.
I was intrigued with the way they use it in one of their component S2Dao. Basically you only need to create interface DAO class and the framework automatically, changes the code on runtime and creates intermediate class that get called in the middle. Hence DB transactions codes are automatically added to the class. I was wondering, is there any step by step explanation on how this is done? Can java change code on runtime and change the method on runtime?
Are good reference on how this is done? I just want to know how the framework is doing this.
Yes, it is possible to do dynamic implementations of an interface at runtime, and to manipulate the compiled bytecode also.
Java provides a built-in mechanism to implement interfaces at run-time, called dynamic proxy classes.
There are also good libraries like cglib or javassist, that allow you not only to implement interfaces, but also to extend classes and to manipulate bytecode at run-time (to change the behavior of a method, for example). Frameworks like Spring and Hibernate use libraries like these to make their magic, so your framework may be using some of these also.
NOTE: If you are curious, these libraries can "tweak" the bytecode because instead of using the default ClassLoader of the JVM, they load your classes using their own ClassLoader, so they have total control of every single byte of the loaded class, and they can do whatever they want with them :).
I'm trying to identify places where annotation names are the same or similar to compile a list of these things to make sure our team knows where possible points of confusion can be found. For example, Guice #provides and RESTeasy #provider are similar enough in spelling but different enough in semantics as to confuse people so I'd like to call that out explicitly and explain the differences.
What I'm looking for is a tool or even a website that enumerates the annotations associated with packages. This might be a pipe dream, but before I manually start going through and collecting these things I thought I'd check.
I was considering writing one based on Javadoc that simply only pulled in the annotations but I don't have access to Java source files in many cases.
Any thoughts or suggestions?
In Eclipse you can use the standard method "Search for references" (context menu of a used annotation References -> Project) and you are getting a list where the annotations is used within your project.
I suggest to scan for annotations yourself and generate a list for that.
You can do that by writing your own implementation of an annotation processer, i.e. extend AbstractProcessor. Within this processor you can write a text file containing all Annotations. You can add this processor to your build procedure, then it will execute the processor when you build the project.
Another way to do this is using the Google Reflections library. This might be a bit more work since you would need to write a small programm to fetch the annotations and write the file.
I wrote such a tool: https://github.com/MoserMichael/ls-annotations
it decompiles the byte code and lists declarations (classes, functions, variables) with annotations only. You can also use it to find all classes/interfaces derived from a given class/inerface - and all the classes/interfaces derived from a given class/interface.
The tool uses the asm library to scan class files and to extract annotations. it can detect annotations with retention policy CLASS and RUNTIME. It can't detect annotations with retention policy SOURCE that are not put into bytecode, for example #Override is one of these.
Why not scanning your classpath and export all used annotations? Then just use some simple parsing / text compare to see the elements with almost the same name?