Thursday, September 25, 2014

Don't write boilerplate code for java objects any longer

When you write java classes, you usually have many properties you expose via getter/setter methods.
This gives a lot of code, which is not very interesting to write and maintain, but for the sake of java bean (and other reasons) you will do it correctly.

It's one of the features of the IDE that you can let them generate the proper getter/setter methods.
Usually it's called something like "Encapsulate property access". You then select the properties you wish setter/getter created and you are done, the idea puts the correct code in your class.

Nice, but, it could be simpler.
The drawback of all this is, that you fill up your class file with a lot of set/get code which you usually don't want to see.

Fortunally there is help for this as well.
Look at the project Lombook.

With this project you write your class like this:

01 import lombok.AccessLevel;
02 import lombok.Setter;
03 import lombok.Data;
04 import lombok.ToString;
05
06 @Data public class DataExample {
07   private final String name;
08   @Setter(AccessLevel.PACKAGEprivate int age;
09   private double score;
10   private String[] tags;
11   
12   @ToString(includeFieldNames=true)
13   @Data(staticConstructor="of")
14   public static class Exercise<T> {
15     private final String name;
16     private final T value;
17   }
18 }
 
These 18 lines of code do the same as these 118 lines of plain java coding:
001 import java.util.Arrays;

002
003 public class DataExample {
004   private final String name;
005   private int age;
006   private double score;
007   private String[] tags;
008   
009   public DataExample(String name) {
010     this.name = name;
011   }
012   
013   public String getName() {
014     return this.name;
015   }
016   
017   void setAge(int age) {
018     this.age = age;
019   }
020   
021   public int getAge() {
022     return this.age;
023   }
024   
025   public void setScore(double score) {
026     this.score = score;
027   }
028   
029   public double getScore() {
030     return this.score;
031   }
032   
033   public String[] getTags() {
034     return this.tags;
035   }
036   
037   public void setTags(String[] tags) {
038     this.tags = tags;
039   }
040   
041   @Override public String toString() {
042     return "DataExample(" this.getName() ", " this.getAge() ", " this.getScore() ", " + Arrays.deepToString(this.getTags()) ")";
043   }
044   
045   protected boolean canEqual(Object other) {
046     return other instanceof DataExample;
047   }
048   
049   @Override public boolean equals(Object o) {
050     if (o == thisreturn true;
051     if (!(instanceof DataExample)) return false;
052     DataExample other = (DataExampleo;
053     if (!other.canEqual((Object)this)) return false;
054     if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false;
055     if (this.getAge() != other.getAge()) return false;
056     if (Double.compare(this.getScore(), other.getScore()) != 0return false;
057     if (!Arrays.deepEquals(this.getTags(), other.getTags())) return false;
058     return true;
059   }
060   
061   @Override public int hashCode() {
062     final int PRIME = 59;
063     int result = 1;
064     final long temp1 = Double.doubleToLongBits(this.getScore());
065     result = (result*PRIME(this.getName() == null this.getName().hashCode());
066     result = (result*PRIMEthis.getAge();
067     result = (result*PRIME(int)(temp1 ^ (temp1 >>> 32));
068     result = (result*PRIME+ Arrays.deepHashCode(this.getTags());
069     return result;
070   }
071   
072   public static class Exercise<T> {
073     private final String name;
074     private final T value;
075     
076     private Exercise(String name, T value) {
077       this.name = name;
078       this.value = value;
079     }
080     
081     public static <T> Exercise<T> of(String name, T value) {
082       return new Exercise<T>(name, value);
083     }
084     
085     public String getName() {
086       return this.name;
087     }
088     
089     public T getValue() {
090       return this.value;
091     }
092     
093     @Override public String toString() {
094       return "Exercise(name=" this.getName() ", value=" this.getValue() ")";
095     }
096     
097     protected boolean canEqual(Object other) {
098       return other instanceof Exercise;
099     }
100     
101     @Override public boolean equals(Object o) {
102       if (o == thisreturn true;
103       if (!(instanceof Exercise)) return false;
104       Exercise<?> other = (Exercise<?>o;
105       if (!other.canEqual((Object)this)) return false;
106       if (this.getName() == null ? other.getValue() != null : !this.getName().equals(other.getName())) return false;
107       if (this.getValue() == null ? other.getValue() != null : !this.getValue().equals(other.getValue())) return false;
108       return true;
109     }
110     
111     @Override public int hashCode() {
112       final int PRIME = 59;
113       int result = 1;
114       result = (result*PRIME(this.getName() == null this.getName().hashCode());
115       result = (result*PRIME(this.getValue() == null this.getValue().hashCode());
116       return result;
117     }
118   }
119 }
 
 
 
 
So with project lombok you can concentrate on the real code, and the annotations do expand on build to the boilerplate code.
There are many options in lombok to also generate other things for java classes, be sure to look at the documentation.

There is just one "bad" thing about it:
By definition annotations should not create java code, but in this case I think it is worth the "break" of rules.