gaspersic/java-design-patterns
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

refactoring: execute around idiom (#1945)

Browse Source 
* Refactor execute around the idiom

* fix checkstyle errors

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>
This commit is contained in:
Ilkka Seppälä
2022-01-10 13:34:19 +02:00
committed by GitHub
parent c5492184b7
commit 07ee94d671
3 changed files with 54 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
execute-around/README.md
View File

@ -17,10 +17,10 @@ the user to specify only what to do with the resource.
## Explanation
Real world example
Real-world example
> We need to provide a class that can be used to write text strings to files. To make it easy for
> the user we let our service class open and close the file automatically, the user only has to
> A class needs to be provided for writing text strings to files. To make it easy for
> the user, the service class opens and closes the file automatically. The user only has to
> specify what is written into which file.
In plain words
@ -35,35 +35,50 @@ In plain words
**Programmatic Example**
Let's introduce our file writer class.
`SimpleFileWriter` class implements the Execute Around idiom. It takes `FileWriterAction` as a
constructor argument allowing the user to specify what gets written into the file.
```java
@FunctionalInterface
public interface FileWriterAction {
void writeFile(FileWriter writer) throws IOException;
}
@Slf4j
public class SimpleFileWriter {
public SimpleFileWriter(String filename, FileWriterAction action) throws IOException {
try (var writer = new FileWriter(filename)) {
action.writeFile(writer);
public SimpleFileWriter(String filename, FileWriterAction action) throws IOException {
LOGGER.info("Opening the file");
try (var writer = new FileWriter(filename)) {
LOGGER.info("Executing the action");
action.writeFile(writer);
LOGGER.info("Closing the file");
}
}
}
}
```
To utilize the file writer the following code is needed.
The following code demonstrates how `SimpleFileWriter` is used. `Scanner` is used to print the file
contents after the writing finishes.
```java
FileWriterAction writeHello = writer -> {
writer.write("Hello");
writer.append(" ");
writer.append("there!");
};
new SimpleFileWriter("testfile.txt", writeHello);
FileWriterAction writeHello = writer -> {
writer.write("Gandalf was here");
};
new SimpleFileWriter("testfile.txt", writeHello);
var scanner = new Scanner(new File("testfile.txt"));
while (scanner.hasNextLine()) {
LOGGER.info(scanner.nextLine());
}
```
Here's the console output.
```
21:18:07.185 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Opening the file
21:18:07.188 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Executing the action
21:18:07.189 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Closing the file
21:18:07.199 [main] INFO com.iluwatar.execute.around.App - Gandalf was here
```
## Class diagram
@ -74,8 +89,7 @@ To utilize the file writer the following code is needed.
Use the Execute Around idiom when
* You use an API that requires methods to be called in pairs such as open/close or
allocate/deallocate.
* An API requires methods to be called in pairs such as open/close or allocate/deallocate.
## Credits