kandi X-RAY | JavaTutorial Summary
kandi X-RAY | JavaTutorial Summary
你可以在 [Google Play] 或 [Pubu] 上，取得本系列的電子書版本。.
Top functions reviewed by kandi - BETA
- Create the DvdD tables .
- The main method .
- Finds a director with the specified name .
- Add a new dvd .
- Return a list of Dvd objects .
- Returns a String representation of this DvdObject .
- Gets a user .
- Add a new Dvd .
- Set the DvdLibrary service .
- Factory method to create an Account object .
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I really can't understand the reason for this error. I ran the sample application. It works correctly. Same code but cannot load correctly. I think the error is due to the version difference. Anyone have any suggestions for a solution?
The web service I created...
ANSWERAnswered 2021-Mar-02 at 20:55
The problem is that you are using Jersey 2.x, but your Multipart dependency is for Jersey 1.x. The two Jersey versions are incompatible. So the
@FormDataParam annotation you using is just being ignored. That's why what you are getting in the
InputStream is the entire multipart entity instead of just the file part.
What you need to do is get rid of all your Jersey 1.x dependencies then add the Jersey 2.x
I am new to kafka-spark streaming and trying to implement the examples from spark documentation with a Protocol buffer serializer/deserializer. So far I followed the official tutorials on
and now I stuck on with the following problem. This question might be similar with this post How to deserialize records from Kafka using Structured Streaming in Java?
I already implemented successful the serializer which writes the messages on the kafka topic. Now the task is to consume it with spark structured streaming with a custom deserializer....
ANSWERAnswered 2019-Jul-05 at 02:49
Did you miss this section of the documentation?
Note that the following Kafka params cannot be set and the Kafka source or sink will throw an exception:
- key.deserializer: Keys are always deserialized as byte arrays with ByteArrayDeserializer. Use DataFrame operations to explicitly deserialize the keys.
- value.deserializer: Values are always deserialized as byte arrays with ByteArrayDeserializer. Use DataFrame operations to explicitly deserialize the values.
You'll have to register a UDF that invokes your deserializers instead
I'm struggling to understand the overall use of Abstraction in Java.
I have been working off an example in this link: https://javatutorial.net/java-abstraction-example I understand the implementation of it but I don't understand why its even necessary. Why is their a calculateSalary method made in the Employee class if they are just going to made again in the 2 subclasses?...
ANSWERAnswered 2019-Feb-10 at 07:45
The overall use of abstraction is decoupling. To work with an
Employee, one does not need to know the implementation, only the interface and its contracts. This is, for example, used for
Collections.sort(List list): the programmers of
Collections.sort(...) did not need to know the implementation of a specific list in order to sort it. This provides the benefit that the implementation support future code that conforms to the
List interface. This question is related in that respect (#selfPromotion). Less coupling leads to less friction and overall less fragile code.
That said, the example you provided is a poor one since it violates the Single Responsibility Principle: It is not the responsibility of an
Employee instance to calculate the salary. For this, you should have a separate object that calculates the salary, based on an
Employee-instance and some hours worked. Internally, this Uber-calculator could use a Chain of Responsibility, which hold one
Employee-Implementation, decoupling the
Employee from how her/his salary is calculated. This provides the added benefit of extensability and flexibility: if the way a salary is calculated changes (e.g. maybe the company switches policy so that each
FullTimeEmployee earns the same salary, or maybe the company wants to calculate the salary on a by-week instead of a by-month basis), other services using the
FullTimeEmployee say unaffected).
val persons = Person()
- Person is a scala class generated using protobuf compiler in scala.
- I just wanted to read a pdub(a binary file) and append some more content in it and then write it back to disk.
- following this link https://developers.google.com/protocol-buffers/docs/javatutorial, its in java but for my case i am trying in scala.
Error : Type mismatch, expected: CodedInputStream, actual: FileInputStream...
ANSWERAnswered 2018-Dec-17 at 17:14
You have to provide a CodedInputStream.
Came across this block of Java code from the Google Protocol Buffers Tutorial:...
ANSWERAnswered 2018-Apr-17 at 18:19
That style of formatting is not completely normal in most code but when you are using a builder it is quite common since part of using a builder is the ability to chain calls to look like what you posted for readability.
It replaces a long parameter list which also tend to have strange formatting.
The dots indicate a call to the return value of the method on the previous line (Note that the line before each line starting with "." has no semi-colon). Every builder method returns "this" so that it can be chained in this way.
If one wasn't interested in readability your example could be re-written like this:
I have created a java cucumber maven project. Now I want to push all report in dropbox once execution of test script is done.
My main goal is to push report folder on Dropbox.
I am using below maven dependency:...
ANSWERAnswered 2017-Nov-03 at 13:32
The fact that it stuck on that line is normal. The program just expects the user's input from the console in order to proceed to the next line of code.
I have this code from here https://javatutorial.net/capture-network-packages-java But it does not return the src or destination ips. I can see the ip via...
ANSWERAnswered 2017-Aug-08 at 20:36
Really simple they changed the code. Instead of
sIP = ip.source(); dIP = ip.destination();
I am trying to convert a Spark RDD to a Spark SQL dataframe with
toDF(). I have used this function successfully many times, but in this case I'm getting a compiler error:
ANSWERAnswered 2017-Apr-29 at 19:51
The reason for the compilation error is that there's no
Encoder in scope to convert a
com.example.protobuf.SensorData to a
ExpressionEncoders to be exact) are used to convert
InternalRow objects into JVM objects according to the schema (usually a case class or a Java bean).
There's a hope you can create an
Encoder for the custom Java class using
Creates an encoder for Java Bean of type T.
Something like the following:
The JavaTutorials have this to say on
IdentityHashMapis an identity-based
Mapimplementation based on a hash table. This class is useful for topology-preserving object graph transformations, such as serialization or deep-copying. To perform such transformations, you need to maintain an identity-based "node table" that keeps track of which objects have already been seen. Identity-based maps are also used to maintain object-to-meta-information mappings in dynamic debuggers and similar systems. Finally, identity-based maps are useful in thwarting "spoof attacks" that are a result of intentionally perverse equals methods because
IdentityHashMapnever invokes the
equalsmethod on its keys. An added benefit of this implementation is that it is fast.
Could someone please explain in Simple English what is meant by both
- "identity-based Map" and
- "topology-preserving object graph transformations"?
ANSWERAnswered 2017-Jan-11 at 10:43
Read the Javadoc - as you always should if you need to understand a class.
This class implements the Map interface with a hash table, using reference-equality in place of object-equality when comparing keys (and values). In other words, in an
IdentityHashMap, two keys
k2are considered equal if and only if
(k1==k2). (In normal Map implementations (like
HashMap) two keys
k2are considered equal if and only if
(k1==null ? k2==null : k1.equals(k2)).)
A typical use of this class is topology-preserving object graph transformations, such as serialization or deep-copying. To perform such a transformation, a program must maintain a "node table" that keeps track of all the object references that have already been processed. The node table must not equate distinct objects even if they happen to be equal.
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