Bean Transformation samples
Simple case:
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger id;
private final List<FromSubBean> subBeanList; private final String name;
private List<String> list; private final List<String> list;
private final FromSubBean subObject; private final List<ToSubBean> subBeanList;
private ImmutableToSubFoo subObject;
// all constructors // all args constructor
// getters and setters... // getters and setters...
}
And one line code as:
ToBean toBean = beanUtils.getTransformer().transform(fromBean, ToBean.class);
Different field names copy:
From class and To class with different field names:
public class FromBean { public class ToBean {
private final String name; private final String differentName;
private final int id; private final int id;
private final List<FromSubBean> subBeanList; private final List<ToSubBean> subBeanList;
private final List<String> list; private final List<String> list;
private final FromSubBean subObject; private final ToSubBean subObject;
// getters...
public ToBean(final String differentName,
final int id,
} final List<ToSubBean> subBeanList,
final List<String> list,
final ToSubBean subObject) {
this.differentName = differentName;
this.id = id;
this.subBeanList = subBeanList;
this.list = list;
this.subObject = subObject;
}
// getters...
}
And one line code as:
beanUtils.getTransformer().withFieldMapping(new FieldMapping<>("name", "differentName")).transform(fromBean, ToBean.class);
it is also possible to map a field in the source class into multiple fields in the destination object.
Given the following source class:
public class SourceClass {
private final String name;
private final int id;
}
the following destination class:
public class DestinationClass {
private final String name;
private final int id;
private final int index;
}
and the following operations:
var sourceObj = new SourceClass("foo", 123);
var multipleFieldMapping = new FieldMapping<>("id", "index", "identifier");
var destObj = new BeanUtils().getBeanTransformer()
.withFieldMapping(multipleFieldMapping)
.transform(sourceObj, DestinationClass.class);
System.out.println("name = " + destObj.getName());
System.out.println("id = " + destObj.getId());
System.out.println("index = " + destObj.getIndex());
the output will be:
name = foo
id = 123
index = 123
Mapping destination fields with correspondent fields contained inside one of the nested objects in the source object:
Assuming that the object FromSubBean is declared as follow:
public class FromSubBean {
private String serialNumber;
private Date creationDate;
// getters and setters...
}
and our source object and destination object are described as follow:
public class FromBean { public class ToBean {
private final int id; private final int id;
private final String name; private final String name;
private final FromSubBean subObject; private final String serialNumber;
private final Date creationDate;
// all args constructor // all args constructor
// getters... // getters...
} }
the fields: serialNumber and creationDate needs to be retrieved from subObject, this can be done by defining the whole path to the end property:
FieldMapping serialNumberMapping = new FieldMapping<>("subObject.serialNumber", "serialNumber");
FieldMapping creationDateMapping = new FieldMapping<>("subObject.creationDate", "creationDate");
beanUtils.getTransformer()
.withFieldMapping(serialNumberMapping, creationDateMapping)
.transform(fromBean, ToBean.class);
Different field names defining constructor args:
public class FromBean { public class ToBean {
private final String name; private final String differentName;
private final int id; private final int id;
private final List<FromSubBean> subBeanList; private final List<ToSubBean> subBeanList;
private final List<String> list; private final List<String> list;
private final FromSubBean subObject; private final ToSubBean subObject;
// all args constructor
// getters...
public ToBean(@ConstructorArg("name") final String differentName,
@ConstructorArg("id") final int id,
} @ConstructorArg("subBeanList") final List<ToSubBean> subBeanList,
@ConstructorArg(fieldName ="list") final List<String> list,
@ConstructorArg("subObject") final ToSubBean subObject) {
this.differentName = differentName;
this.id = id;
this.subBeanList = subBeanList;
this.list = list;
this.subObject = subObject;
}
// getters...
}
And one line code as:
ToBean toBean = beanUtils.getTransformer().transform(fromBean, ToBean.class);
Different field names and types applying transformation through lambda function:
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger identifier;
private final List<FromSubBean> subBeanList; private final String name;
private List<String> list; private final List<String> list;
private final FromSubBean subObject; private final List<ImmutableToSubFoo> nestedObjectList;
private final String locale; private final Locale locale;
private ImmutableToSubFoo nestedObject;
// constructors... // constructors...
// getters and setters... // getters and setters...
} }
FieldTransformer<BigInteger, BigInteger> fieldTransformer = new FieldTransformer<>("identifier", BigInteger::negate);
FieldTransformer<String, Locale> localeTransformer = new FieldTransformer<>("locale", Locale::forLanguageTag);
beanUtils.getTransformer()
.withFieldMapping(new FieldMapping<>("id", "identifier"))
.withFieldTransformer(fieldTransformer).transform(fromBean, ToBean.class)
.withFieldTransformer(localeTransformer);
It's also possible to apply the same transformation function on multiple fields. Taking as an example the above bean and assuming that we would negate both the id and the identifier, the transformer function has to be defined as follows:
FieldTransformer<BigInteger, BigInteger> fieldTransformer = new FieldTransformer<>(List.of("identifier", "index"), BigInteger::negate);
Assign a default value in case of missing field in the source object:
Assign a default value in case of a missing field in the source object:
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger id;
private final String name;
private String notExistingField; // this will be null and no exceptions will be raised
// constructors... // constructors...
// getters... // getters and setters...
} }
And one line code as:
ToBean toBean = beanUtils.getTransformer()
.setDefaultValueForMissingField(true).transform(fromBean, ToBean.class);
Disable the default value set for primitive types in case they are null:
BULL by default sets the default value for all primitive types fields in case their value is in the source object. Given the following Java Bean:
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger id;
private final String name;
// constructors... // constructors...
// getters... // getters and setters...
} }
in case the field id in the FromBean object is null, the value assigned the correspondent field in the ToBean object will be 0.
To disable this you can simply do:
ToBean toBean = beanUtils.getTransformer()
.setDefaultValueForMissingPrimitiveField(false).transform(fromBean, ToBean.class);
in this case, the field id after the transformation will be null
Applying a transformation function in case of missing fields in the source object:
Assign a default value in case of a missing field in the source object:
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger id;
private final String name;
private String notExistingField; // this will have value: sampleVal
// all args constructor // constructors...
// getters... // getters and setters...
} }
And one line code as:
FieldTransformer<String, String> notExistingFieldTransformer = new FieldTransformer<>("notExistingField", () -> "sampleVal");
ToBean toBean = beanUtils.getTransformer()
.withFieldTransformer(notExistingFieldTransformer)
.transform(fromBean, ToBean.class);
Apply a transformation function on a field contained in a nested object:
This example shows how a lambda transformation function can be applied to a nested object field.
Given:
public class FromBean { public class ToBean {
private final String name; private final String name;
private final FromSubBean nestedObject; private final ToSubBean nestedObject;
// all args constructor // all args constructor
// getters... // getters...
} }
and
public class ToSubBean {
private final String name;
private final long index;
}
Assuming that the lambda transformation function should be applied only to field: name contained into the ToSubBean object, the transformation function has to be defined as
follow:
FieldTransformer<String, String> nameTransformer = new FieldTransformer<>("nestedObject.name", StringUtils::capitalize);
ToBean toBean = beanUtils.getTransformer()
.withFieldTransformer(nameTransformer)
.transform(fromBean, ToBean.class);
Map a primitive type field in the source object into a nested object:
This example shows how to map a primitive field into a nested object into the destination one.
Given:
public class FromBean { public class ToBean {
private final String name; private final String name;
private final FromSubBean nestedObject; private final ToSubBean nestedObject;
private final int x;
// all args constructor // all args constructor
// getters... // getters...
} }
and
public class ToSubBean {
private final int x;
// all args constructor
} // getters...
Assuming that the value x should be mapped into the field: x contained into the ToSubBean object, the field mapping has to be defined as
follow:
ToBean toBean = beanUtils.getTransformer()
.withFieldMapping(new FieldMapping<>("x", "nestedObject.x"));
Apply a transformation function on all fields matching with the given one:
This example shows how a lambda transformation function can be applied to all fields matching with the given one independently from their position.
Given:
public class FromBean { public class ToBean {
private final String name; private final String name;
private final FromSubBean nestedObject; private final ToSubBean nestedObject;
// all args constructor // all args constructor
// getters... // getters...
} }
and
public class FromSubBean { public class ToSubBean {
private final String name; private final String name;
private final long index; private final long index;
// all args constructor // all args constructor
// getters... // getters...
} }
Assuming that the lambda transformation function should be applied only to the field: name contained in the ToSubBean object, the transformation function has to be defined
as
follow:
FieldTransformer<String, String> nameTransformer = new FieldTransformer<>("name", StringUtils::capitalize);
ToBean toBean = beanUtils.getTransformer()
.setFlatFieldNameTransformation(true)
.withFieldTransformer(nameTransformer)
.transform(fromBean, ToBean.class);
Static transformer function:
List<FromFooSimple> fromFooSimpleList = Arrays.asList(fromFooSimple, fromFooSimple);
can be transformed as follow:
Function<FromFooSimple, ImmutableToFooSimple> transformerFunction = BeanUtils.getTransformer(ImmutableToFooSimple.class);
List<ImmutableToFooSimple> actual = fromFooSimpleList.stream()
.map(transformerFunction)
.collect(Collectors.toList());
or if you have a pre-configured transformer:
Function<FromFooSimple, ImmutableToFooSimple> transformerFunction = BeanUtils.getTransformer(<yourPreconfiguredTransformer>, ImmutableToFooSimple.class);
List<ImmutableToFooSimple> actual = fromFooSimpleList.stream()
.map(transformerFunction)
.collect(Collectors.toList());
Enable Java Beans validation:
Assuming that the field: id in the fromBean instance is null.
public class FromBean { public class ToBean {
private final String name; @NotNull
private final BigInteger id; public BigInteger id;
private final String name;
// all args constructor // all args constructor
// getters... // getters and setters...
} }
adding the following configuration an exception will be thrown:
ToBean toBean = beanUtils.getTransformer()
.setValidationEnabled(true)
.transform(fromBean, ToBean.class);
Copy on an existing instance:
Given:
public class FromBean { public class ToBean {
private final String name; private String name;
private final FromSubBean nestedObject; private ToSubBean nestedObject;
// all args constructor // constructor
// getters... // getters and setters...
} }
if you need to perform the copy on an already existing object, just do:
ToBean toBean = new ToBean();
beanUtils.getTransformer().transform(fromBean, toBean);
Skip transformation on a given set of fields:
Given:
public class FromBean { public class ToBean {
private final String name; private String name;
private final FromSubBean nestedObject; private ToSubBean nestedObject;
// all args constructor // constructor
// getters... // getters and setters...
} }
public class FromBean2 {
private final int index;
private final FromSubBean nestedObject;
// all args constructor
// getters...
}
if you need to skip the transformation for a given field, just do:
ToBean toBean = new ToBean();
beanUtils.getTransformer()
.skipTransformationForField("nestedObject")
.transform(fromBean, toBean);
where nestedObject is the name of the field in the destination object.
This feature allows us to transform an object keeping the data from different sources.
To better explain this function let's assume that the ToBean (defined above) should be transformed as follow:
namefield value has been taken from theFromBeanobjectnestedObjectfield value has been taken from theFromBean2object
the objective can be reached by doing:
// create the destination object
ToBean toBean = new ToBean();
// execute the first transformation skipping the copy of: 'nestedObject' field that should come from the other source object
beanUtils.getTransformer()
.skipTransformationForField("nestedObject")
.transform(fromBean, toBean);
// then execute the transformation skipping the copy of: 'name' field that should come from the other source object
beanUtils.getTransformer()
.skipTransformationForField("name")
.transform(fromBean2, toBean);
Not existing field in the source object:
In case the destination class has a field that does not exist in the source object, but it contains a getter method returning the value, the library should gets the field value from that method.
public class FromBean { public class ToBean {
private final BigInteger id;
public BigInteger getId() {
return BigInteger.TEN; // all args constructor
} // getters...
}
}
And one line code as:
ToBean toBean = beanUtils.getTransformer().transform(fromBean, ToBean.class);
Transform primitive types automatically
Given the following Java Bean:
public class FromBean { public class ToBean {
private final String indexNumber; private final int indexNumber;
private final BigInteger id; public Long id;
// constructors... // constructors...
// getters... // getters and setters...
} }
as, by default the primitive type conversion is disabled, to get the above object converted we should have
implemented transformer functions for both field indexNumber and id, but this can be done automatically by enabling the
the functionality described above.
Transformer transformer = beanUtils.getTransformer()
.setPrimitiveTypeConversionEnabled(true);
ToBean toBean = transformer.transform(fromBean, ToBean.class);
IMPORTANT: The primitive type transformation (if enabled) is executed before any other FieldTransformer function is defined on a specific field.
This means that once the FieldTransformer function will be executed the field value has already been transformed.
Transform Java Record
Simple case:
public record FromFooRecord(BigInteger id, String name) { public record RecordToFoo(BigInteger id, String name) {
} }
And one line code as:
var toBean = beanUtils.getTransformer().transform(fromBean, RecordToFoo.class);
More sample beans can be found in the test package: com.expediagroup.beans.sample or on
DZone: How to Transform Any Type of Java Bean With BULL