After reading about the remote shell in the Spring Boot documentation I started playing around with it. I implemented a new Command that produces a Stream of one of my database entities called company.
This works fine. So I want to output my stream of companies in the console. This is done by calling toString() by default. While this seams reasonable there is also a way to get nicer results by using a Renderer.
Implementing one should be straight forward as I can delegate most of the work to one of the already existing ones. I use MapRenderer.
class CompanyRenderer extends Renderer<Company> {
private final mapRenderer = new MapRenderer()
#Override Class<Company> getType() { Company }
#Override LineRenderer renderer(Iterator<Company> stream) {
def list = []
stream.forEachRemaining({
list.add([id: it.id, name: it.name])
})
return mapRenderer.renderer(list.iterator())
}
}
As you can see I just take some fields from my entity put them into a Mapand then delegate to a instance of MapRenderer to do the real work.
TL;DR
Only problem is: How do I register my Renderer with CRaSH?
Links
Spring Boot documentation http://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-remote-shell.html
CRaSH documentation (not helping) http://www.crashub.org/1.3/reference.html#_renderers
Related
I need to write an application startup event listener, here I have an #EventListener:
#EventListener
public void onApplicationEvent(ApplicationStartedEvent startedEvent)
How do I go with this? What I have done until now is, wrote many other unit tests but don't understand if I should (somehow) create an object for the ApplicationStartedEvent which doesn't sound right.
Other questions on SO like this one provide information about creating tests for custom events but this isn't a custom event and I don't want to create this object manually.
I solved it differently as I wanted to unit-test this, but seems like we can only write an Integration Test for this.
Used the following to create sample data:
private static final EasyRandomParameters EASY_RANDOM_PARAMETERS = new EasyRandomParameters()
.seed(123L)
.objectPoolSize(100)
.randomizationDepth(3)
.charset(StandardCharsets.UTF_8)
.timeRange(LocalTime.of(9, 0), LocalTime.of(17, 0))
.stringLengthRange(5, 50)
.collectionSizeRange(1, 10)
.scanClasspathForConcreteTypes(true)
.overrideDefaultInitialization(false)
.ignoreRandomizationErrors(true);
public static <T> T create(Class<T> ofType) {
EasyRandom easyRandom = new EasyRandom(EASY_RANDOM_PARAMETERS);
return easyRandom.nextObject(ofType);
}
And used it like:
ApplicationStartedEvent applicationStartedEvent = create(ApplicationStartedEvent.class);
Then called the required method. Not exactly the event listener of course but did the job.
Currently using reddison, creating a redissonClient and trying to poll data from redis server. I can see the data in the redis db if I check via redis-cli but when I look at the string value in my java application it is always the first 8 characters of the string and no more. Not sure why it won't give me the whole value.
I've tried using the .peek() method as well and I see the same symptom in that I only get 8 characters of the string returned.
Here is the main part of the code I can provide more details as needed:
#Service
#Slf4j
public class RedisConsumer {
RedisConfig redisConfig;
//RQueue<String> redisQueue;
RBlockingQueue<String> redisQueue;
#Autowired
RedisConsumer(RedisConfig redisConfig) {
this.redisConfig = redisConfig;
}
public void pollAuditQueue() {
//Redisson
redisQueue.add("{JSON string here snipped out for brevity}");
String item = redisQueue.poll();
if (!Objects.isNull(item)) {
log.info("I found this item: " + item);
} else {
log.info("Nothing in queue...");
}
}
#PostConstruct
private void init() throws Exception {
RedissonClient redissonClient = redisConfig.redisson();
redisQueue = redissonClient.getBlockingQueue("test");
while(true) {
pollAuditQueue();
Thread.sleep(5000);
}
}
When I look at the print statement in my console I see:
I found this item: {"AuditEv
When I check the redis-cli I can see the whole value:
1) "\xfc\t{\"AuditEvent\":{\"timestamp\":\"2018-11-27 04:31:47.818000+0000\" snipped the rest out for brevity}"
Lastly if I check that the item was removed from Redis after being polled in the Java app I can confirm that it is.
Any help would be great since it's not throwing any specific error I'm not finding any resources online to help address it.
I've found one thing I didn't notice in my earlier testing. When I manually insert using the redis cli I was replicating what my first tests through Java did which put the \xfc\t at the front which can be seen in my sample above.
Just now when I used redisQueue.add from within my application I noticed in redis it has \xfc\x80\x90\x01 instead and those do return the entire string to me in my application. I assume then this has to do with memory allocation somehow? I'm marking the question as resolved as I am no longer experiencing the issue. If anyone can drop on comment on what those letter/numbers mean though it may be meaningful for anyone that reads this post later. Once I have researched it I will add that comment myself if no one has beat me to it!
Add encoding:
RMap map = redisson.getMap("SessionMap"); -->
RMap map = redisson.getMap("SessionMap", new StringCodec("UTF-8"));
Is there a way to pass data to dependencies registered with either Execution Context Scope or Lifetime Scope in Simple Injector?
One of my dependencies requires a piece of data in order to be constructed in the dependency chain. During HTTP and WCF requests, this data is easy to get to. For HTTP requests, the data is always present in either the query string or as a Request.Form parameter (and thus is available from HttpContext.Current). For WCF requests, the data is always present in the OperationContext.Current.RequestContext.RequestMessage XML, and can be parsed out. I have many command handler implementations that depend on an interface implementation that needs this piece of data, and they work great during HTTP and WCF scoped lifestyles.
Now I would like to be able to execute one or more of these commands using the Task Parallel Library so that it will execute in a separate thread. It is not feasible to move the piece of data out into a configuration file, class, or any other static artifact. It must initially be passed to the application either via HTTP or WCF.
I know how to create a hybrid lifestyle using Simple Injector, and already have one set up as hybrid HTTP / WCF / Execution Context Scope (command interfaces are async, and return Task instead of void). I also know how to create a command handler decorator that will start a new Execution Context Scope when needed. The problem is, I don't know how or where (or if I can) "save" this piece of data so that is is available when the dependency chain needs it to construct one of the dependencies.
Is it possible? If so, how?
Update
Currently, I have an interface called IProvideHostWebUri with two implementations: HttpHostWebUriProvider and WcfHostWebUriProvider. The interface and registration look like this:
public interface IProvideHostWebUri
{
Uri HostWebUri { get; }
}
container.Register<IProvideHostWebUri>(() =>
{
if (HttpContext.Current != null)
return container.GetInstance<HttpHostWebUriProvider>();
if (OperationContext.Current != null)
return container.GetInstance<WcfHostWebUriProvider>();
throw new NotSupportedException(
"The IProvideHostWebUri service is currently only supported for HTTP and WCF requests.");
}, scopedLifestyle); // scopedLifestyle is the hybrid mentioned previously
So ultimately unless I gut this approach, my goal would be to create a third implementation of this interface which would then depend on some kind of context to obtain the Uri (which is just constructed from a string in the other 2 implementations).
#Steven's answer seems to be what I am looking for, but I am not sure how to make the ITenantContext implementation immutable and thread-safe. I don't think it will need to be made disposable, since it just contains a Uri value.
So what you are basically saying is that:
You have an initial request that contains some contextual information captured in the request 'header'.
During this request you want to kick off a background operation (on a different thread).
The contextual information from the initial request should stay available when running in the background thread.
The short answer is that Simple Injector does not contain anything that allows you to do so. The solution is in creating a piece of infrastructure that allows moving this contextual information along.
Say for instance you are processing command handlers (wild guess here ;-)), you can specify a decorator as follows:
public class BackgroundProcessingCommandHandlerDecorator<T> : ICommandHandler<T>
{
private readonly ITenantContext tenantContext;
private readonly Container container;
private readonly Func<ICommandHandler<T>> decorateeFactory;
public BackgroundProcessingCommandHandlerDecorator(ITenantContext tenantContext,
Container container, Func<ICommandHandler<T>> decorateeFactory) {
this.tenantContext = tenantContext;
this.container = container;
this.decorateeFactory = decorateeFactory;
}
public void Handle(T command) {
// Capture the contextual info in a local variable
// NOTE: This object must be immutable and thread-safe.
var tenant = this.tenantContext.CurrentTenant;
// Kick off a new background operation
Task.Factory.StartNew(() => {
using (container.BeginExecutionContextScope()) {
// Load a service that allows setting contextual information
var context = this.container.GetInstance<ITenantContextApplier>();
// Set the context for this thread, before resolving the handler
context.SetCurrentTenant(tenant);
// Resolve the handler
var decoratee = this.decorateeFactory.Invoke();
// And execute it.
decoratee.Handle(command);
}
});
}
}
Note that in the example I make use of an imaginary ITenantContext abstraction, assuming that you need to supply the commands with information about the current tenant, but any other sort of contextual information will obviously do as well.
The decorator is a small piece of infrastructure that allows you to process commands in the background and it is its responsibility to make sure all the required contextual information is moved to the background thread as well.
To be able to do this, the contextual information is captured and used as a closure in the background thread. I created an extra abstraction for this, namely ITenantContextApplier. Do note that the tenant context implementation can implement both the ITenantContext and the ITenantContextApplier interface. If however you define the ITenantContextApplier in your composition root, it will be impossible for the application to change the context, since it does not have a dependency on ITenantContextApplier.
Here's an example:
// Base library
public interface ITenantContext { }
// Business Layer
public class SomeCommandHandler : ICommandHandler<Some> {
public SomeCommandHandler(ITenantContext context) { ... }
}
// Composition Root
public static class CompositionRoot {
// Make the ITenantContextApplier private so nobody can see it.
// Do note that this is optional; there's no harm in making it public.
private interface ITenantContextApplier {
void SetCurrentTenant(Tenant tenant);
}
private class AspNetTenantContext : ITenantContextApplier, ITenantContext {
// Implement both interfaces
}
private class BackgroundProcessingCommandHandlerDecorator<T> { ... }
public static Container Bootstrap(Container container) {
container.RegisterPerWebRequest<ITenantContext, AspNetTenantContext>();
container.Register<ITenantContextApplier>(() =>
container.GetInstance<ITenantContext>() as ITenantContextApplier);
container.RegisterDecorator(typeof(ICommandHandler<>),
typeof(BackgroundProcessingCommandHandlerDecorator<>));
}
}
A different approach would be to just make the complete ITenantContext available to the background thread, but to be able to pull this off, you need to make sure that:
The implementation is immutable and thus thread-safe.
The implementation doesn't require disposing, because it will typically be disposed when the original request ends.
I have combed through SO, and have found many questions on the topic of my problem but do not answer it.
I am setting up an MVC, I have set up things correctly to best of my knowledge but I cannot get the Controller to show in my view. I am working on an assignment that essentially is a program for a Video Rental Store.
First, In a class called RentalStoreGUI, I set up my panels and everything looks good when I run.
RentalStoreEngine model = new RentalStoreEngine();
JList<DVD> list = new JList<DVD>();
list.setModel(model);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.setVisible(true);
list.setSelectedIndex(0);
jScrollPane = new JScrollPane(list);
add(jScrollPane, BorderLayout.CENTER);
add(buttonPanel, BorderLayout.SOUTH);
As you can see I set my model for the list based on another class called RentalStoreEngine() and it implements AbstractListModel. The Abstract List model is functioning when I do class specific testing and all of the necessary methods are implemented. Here is an example of my add method from that class:
public void add(DVD d){
if (d != null){
rentals.add(d);//rentals is an arrayList<DVD> instantiated earlier
fireIntervalAdded(this, rentals.size() - 1, rentals.size() - 1);
}
}
Here is the actionPerformed method, it runs DVD_Dialog which simply gets some input from the user and creates a new DVD object from that.
public void actionPerformed(ActionEvent event) {
if(event.getSource() == rentDVD){
DVD_Dialog = new RentDVDDialog(this, null);
DVD_Dialog.clear();
DVD_Dialog.setVisible(true);
dvd = new DVD(DVD_Dialog.getTitleText(),DVD_Dialog.getRenterText(),
DVD_Dialog.getRentedOnText(), DVD_Dialog.getDueBackText());
if(DVD_Dialog.closeStatus() == true){
model.add(dvd);
}
}
Eclipse gives me no errors, until I run it. I then receive a nullPointerException at the line model.add(dvd); Based on all my research the list.setModel(model) and the fireIntervalAdded method line should update the Jlist on its own. But it does not. And as I said, class specific testing for both the GUI and the Model are producing the desired results, but when it comes to integrating them I am at a loss.
I'm new to Google's Guava library and am interested in Guava's Caching package. Currently I have version 10.0.1 downloaded. After reviewing the documentation, the JUnit tests source code and even after searching google extensively, I still can't figure out how to use the Caching package. The documentation is very short, as if it was written for someone who has been using Guava's library not for a newbie like me. I just wish there are more real world examples on how to use Caching package propertly.
Let say I want to build a cache of 10 non expiring items with Least Recently Used (LRU) eviction method. So from the example found in the api, I build my code like the following:
Cache<String, String> mycache = CacheBuilder.newBuilder()
.maximumSize(10)
.build(
new CacheLoader<String, String>() {
public String load(String key) throws Exception {
return something; // ?????
}
});
Since the CacheLoader is required, I have to include it in the build method of CacheBuilder. But I don't know how to return the proper value from mycache.
To add item to mycache, I use the following code:
mycache.asMap().put("key123", "value123");
To get item from mycache, I use this method:
mycache.get("key123")
The get method will always return whatever value I returned from CacheLoader's load method instead of getting the value from mycache. Could someone kindly tell me what I missed?
Guava's Cache type is generally intended to be used as a computing cache. You don't usually add values to it manually. Rather, you tell it how to load the expensive to calculate value for a key by giving it a CacheLoader that contains the necessary code.
A typical example is loading a value from a database or doing an expensive calculation.
private final FooDatabase fooDatabase = ...;
private final LoadingCache<Long, Foo> cache = CacheBuilder.newBuilder()
.maximumSize(10)
.build(new CacheLoader<Long, Foo>() {
public Foo load(Long id) {
return fooDatabase.getFoo(id);
}
});
public Foo getFoo(long id) {
// never need to manually put a Foo in... will be loaded from DB if needed
return cache.getUnchecked(id);
}
Also, I tried the example you gave and mycache.get("key123") returned "value123" as expected.