Rojo is a Java library for mapping the regular expression into a POJO objects and more! The regex groups are automatically converted to the POJO's field types. The currently supported types are:
- String
- Integer / int
- Short / short
- Long / long
- Float / float
- Double / double
- BigInteger, BigDecimal
- Date
<dependency>
<groupId>com.svetylkovo</groupId>
<artifactId>rojo</artifactId>
<version>1.0.3</version>
</dependency>Let's have an input string which will be used to demonstrate the Rojo's features. We will do some regex matching in a short (completely fictional) document which describes the results of a fruit picking session:
String input = "John picked 7 apples on 2/6/2016.\n" +
"Peter picked only 2 pears on 13/6/2016.\n" +
"Jane collected 5 bananas on 5/7/2016.";Now we'll define our POJO class:
@Regex("([A-Z]\\w+).+(\\d) (\\w+) on (\\d+/\\d+/\\d+)")
public class FruitPicker {
@Group(1)
private String name;
@Group(2)
private int count;
@Group(3)
private String fruitType;
@Group(4)
@DateFormat("dd/MM/yyyy")
private Date date;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
public String getFruitType() {
return fruitType;
}
public void setFruitType(String fruitType) {
this.fruitType = fruitType;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
}To use the POJO matching feature, call the Rojo.of() method. To get the first fruit picker, continue by calling match():
Optional<FruitPicker> firstPicker = Rojo.of(FruitPicker.class).match(input);
firstPicker.ifPresent( picker ->
System.out.println("The first picker is "+picker.getName()+", who picked "+picker.getCount()+" "+picker.getFruitType())
);Console output:
The first picker is John, who picked 7 apples
Note that match() returns an Optional, so if there was no match found, the Optional will be empty. To get a List of all fruit pickers, you will use matchList():
List<FruitPicker> allPickers = Rojo.of(FruitPicker.class).matchList(input);
for ( FruitPicker picker : allPickers) {
System.out.println(picker.getName()+" ("+picker.getCount()+" "+picker.getFruitType()+" on "+picker.getDate()+")");
}Console output:
John (7 apples on Thu Jun 02 00:00:00 CEST 2016)
Peter (2 pears on Mon Jun 13 00:00:00 CEST 2016)
Jane (5 bananas on Tue Jul 05 00:00:00 CEST 2016)
You can achieve the same thing by using the matchStream() directly:
Rojo.of(FruitPicker.class).matchStream(input).forEach( picker ->
System.out.println(picker.getName()+" ("+picker.getCount()+" "+picker.getFruitType()+" on "+picker.getDate()+")")
);Stream can have a lot of advantages. E.g. you can use it just to count all picked fruits:
long total = Rojo.of(FruitPicker.class).matchStream(input)
.collect(Collectors.summingInt(FruitPicker::getCount));
System.out.println("Total fruits collected: "+total);Console output:
Total fruits collected: 14
Imagine a situation where you want to match groups to POJO's fields, where one of those fields is an another POJO class with its own regex, which will match the content of the previously parsed group. Let's define such scenario, where we will match person's name and store his/her height and weight into the Body class, which will have a method to compute a person's BMI index:
@Regex("(\\w+): (.+)")
public class Person {
@Group(1)
private String name;
@Group(2)
private Body body;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Body getBody() {
return body;
}
public void setBody(Body body) {
this.body = body;
}
}@Regex("(\\d+)cm,(\\d+)kg")
public class Body {
@Group(1)
private double height;
@Group(2)
private double weight;
public double getBmi() {
return weight/Math.pow((height/100),2);
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
}We will match this input String and print the results:
String input = "Thomas: 180cm,75kg\n" +
"Jane: 163cm,45kg\n" +
"Mark: 175cm,60kg";
Rojo.of(Person.class).matchStream(input).forEach( person -> {
System.out.println(person.getName()+"'s BMI index is: "+person.getBody().getBmi());
});Console output:
Thomas's BMI index is: 23.148148148148145
Jane's BMI index is: 16.937031879257784
Mark's BMI index is: 19.591836734693878
Rojo can match multiple regex matches for a specific group as a List. If the List's generic type is not a class annotated by @Regex, you have to annotate the specific List field. Let's match people's favorite numbers:
@Regex("(\\w+): (.+)")
public class Person {
@Group(1)
private String name;
@Group(2)
@Regex("\\d+")
private List<Integer> favNumbers;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Integer> getFavNumbers() {
return favNumbers;
}
public void setFavNumbers(List<Integer> favNumbers) {
this.favNumbers = favNumbers;
}
}String input = "Thomas: 1,2,3\n" +
"Jane: 4,5,6\n" +
"Mark: 7,8,9";
Rojo.of(Person.class).matchStream(input).forEach( person -> {
String numbers = person.getFavNumbers().stream()
.map(String::valueOf)
.collect(Collectors.joining(" and "));
System.out.println(person.getName()+"'s favorite numbers are: "+numbers);
});Console output:
Thomas's favorite numbers are: 1 and 2 and 3
Jane's favorite numbers are: 4 and 5 and 6
Mark's favorite numbers are: 7 and 8 and 9
If you want to map a group to a type which is not supported by default, you can specify your own mapper using the @Mapper annotation, which takes a class which implements Function<String, ?> that maps a String to your specified type:
@Regex("(\\w+): (.+)")
public class Person {
@Group(1)
private String name;
@Group(2)
@Mapper(MyBooleanMapper.class)
private boolean evenAge;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isEvenAge() {
return evenAge;
}
public void setEvenAge(boolean evenAge) {
this.evenAge = evenAge;
}
}public class MyBooleanMapper implements Function<String, Boolean> {
@Override
public Boolean apply(String str) {
return Integer.valueOf(str) % 2 == 0;
}
}String input = "Thomas: 20\n" +
"Jane: 21\n" +
"Mark: 22";
Rojo.of(Person.class).matchStream(input).forEach( person -> {
System.out.println("Is "+person.getName()+"'s age even? => "+person.isEvenAge());
});Console output:
Is Thomas's age even? => true
Is Jane's age even? => false
Is Mark's age even? => true
You don't always need to match a POJO bean, but Rojo also enables you to do the "plain matching" in much more convenient way, than if you've used the Java's Pattern.compile() manually. Let's print just the first picker's name:
String input = "John picked 7 apples on 2/6/2016.\n" +
"Peter picked only 2 pears on 13/6/2016.\n" +
"Jane collected 5 bananas on 5/7/2016.";
Optional<String> firstName = Rojo.find("[A-Z]\\w+", input);
firstName.ifPresent( name ->
System.out.println("The first picker is "+name)
);Console output:
The first picker is John
To print out all names you can use asList():
List<String> allNames = Rojo.asList("[A-Z]\\w+", input);
for ( String name : allNames) {
System.out.println(name);
}Console output:
John
Peter
Jane
or the same thing using asStream():
Rojo.asStream("[A-Z]\\w+", input).forEach(System.out::println);In some cases you may want to match for a pair of groups and see the result as a Map<String,String>. You can do that by calling asMap(). Let's find pairs which will contain the picker's name and the count of the fruits that he/she has collected:
Map<String, String> pickersMap = Rojo.asMap("([A-Z]\\w+).+?(\\d)", input);
System.out.println(pickersMap);Console output:
{John=7, Peter=2, Jane=5}
What if we wanted to change all collected fruit names to upper-case? There's a useful replace() method for that:
String replaced = Rojo.replace("\\d \\w+", input, String::toUpperCase);
System.out.println(replaced);Console output:
John picked 7 APPLES on 2/6/2016.
Peter picked only 2 PEARS on 13/6/2016.
Jane collected 5 BANANAS on 5/7/2016.
... for more advanced replacement you can use replaceMatcher().
If you want to do the replacement dealing with the groups directly, it's handy to have them extracted as a lambda function parameters:
String replaced = Rojo.replaceGroup("(\\d) (\\w+)", input, (count, fruit) -> "and ate "+count+" "+fruit.toUpperCase() );
System.out.println(replaced);Console output:
John picked and ate 7 APPLES on 2/6/2016.
Peter picked only and ate 2 PEARS on 13/6/2016.
Jane collected and ate 5 BANANAS on 5/7/2016.
This method allows you to iterate over the regex matches, where it extracts all groups (2 and more, up to 10) into the lambda function arguments:
Rojo.forEach("([A-Z]\\w+).+(\\d) (\\w+) on (\\d+/\\d+/\\d+)", input,
(name, count, fruit, date) -> System.out.println(name + " (" + count + " " + fruit + " on " + date + ")")
);Console output:
John (7 apples on 2/6/2016)
Peter (2 pears on 13/6/2016)
Jane (5 bananas on 5/7/2016)
The same as forEach() except it returns a Stream<String>.
Sometimes you just want to extract the first group only. The firstGroup() method returns a Stream<String>, where each element is the extracted first group in the regex:
String input = "{apple},{banana},{pear}";
Rojo.firstGroup("\\{(.+?)\\}", input)
.forEach(System.out::println);Console output:
apple
banana
pear
Since Rojo.of() and all other plain-matching methods always create a new Pattern instance inside, it might be expensive if you want to do the matching with the same regex on a large amount of different input Strings. For this purpose you may want to store the matcher and re-use it. For POJO matching, you can just store the RojoBeanMatcher instance returned by Rojo.of(), so this code:
SimpleBean bean = Rojo.of(SimpleBean.class)
.match(input).get();will be replaced by:
RojoBeanMatcher<SimpleBean> matcher = Rojo.of(SimpleBean.class);
SimpleBean bean = matcher.match(input).get();For plain-matching there is a Rojo.matcher() method which obtains the RojoMatcher instance, so this code:
List<String> list = Rojo.asList("[a-z]", input);will turn into this one:
RojoMatcher matcher = Rojo.matcher("[a-z]");
List<String> list = matcher.asList(input);- @Regex - here's where you specify your regex pattern as String
- @Flags - if you want to use flags such as Pattern.DOTALL etc.
- @Regex - only for List type of fields which don't use the "nested class matching" (=class annotated by @Regex itself) as a generic type
- @Group - group number that corresponds to the field
- @DateFormat - this annotation is mandatory only for the Date type fields, where you have to specify the date format
- @Mapper - custom mapping of the matched group to your specified type