JarCasting
Bean Utils Light Library
BULL is a Java Bean to Java Bean transformer that recursively copies data from one object to another, it is generic, flexible, reusable, configurable, and incredibly fast. It's the only library able to transform Mutable, Immutable, and Mixed bean without any custom configuration.
Start using
All BULL modules are available on Maven Central:
-
Bean Transformer
<dependency>
<groupId>com.hotels.beans</groupId>
<artifactId>bull-bean-transformer</artifactId>
<version>x.y.z</version>
</dependency>
-
MapTransformer
<dependency>
<groupId>com.hotels.beans</groupId>
<artifactId>bull-map-transformer</artifactId>
<version>x.y.z</version>
</dependency>
The project provides two different builds, one compatible with jdk 8 (or above) and one with jdk 11 or above.
In case you need to integrate it in a jdk 8 (or above project) please refer to CHANGELOG-JDK8 file or CHANGELOG otherwise.
-
Suggestions
Some jdk versions remove the Java Bean constructor's argument names from the compiled code and this may cause problems to the library. On top of that, it's suggested to configure the maven-compiler-plugin, inside your project, as follow:
<build>
...
<pluginManagement>
<plugins>
...
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven.compiler.plugin.version}</version>
<configuration>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
<parameters>true</parameters>
<forceJavacCompilerUse>true</forceJavacCompilerUse>
</configuration>
</plugin>
</plugins>
</pluginManagement>
...
</build>
Maven build
Full build
./mvnw clean install
or on Windows
mvnw.cmd clean install
Skip test coverage and checkstyle check
./mvnw clean install -P relaxed
or on Windows
mvnw.cmd clean install -P relaxed
Features:
- support copy of immutable beans.
- support copy of mutable beans.
- support copy of hybrid beans (some fields private and some not).
- support copy of Java beans without getter and setter methods.
- support copy with Java primitive type.
- support copy with Java Collection type. e.g.
List<BeanA> => List<BeanB> - support copy with nested map fields. e.g.
Map<String, Map<String, String>> - support copy with array containing primitive types. e.g.
String[]=>String[] - support copy with an array type. e.g.
BeanA[]=>BeanB[] - support copy with property name mapping. e.g.
int id => int userId - support copy with recursion copy.
- support validation through annotations.
- support copy of beans with different field's name.
- support lambda function field transformation.
- support copy of java bean built through Builder.
- easy usage, declarative way to define the property mapping (in case of different names), or simply adding the Lombok annotations.
- allows setting the default value for all objects not existing in the source object.
- allows skipping transformation for a given set of fields.
- supports the retrieval of the value from getters if a field does not exist in the source object.
- supports the automatic conversion of primitive types.
Feature samples
- Bean Transformation
- Bean Validation
- Primitive Type conversion
- Map Transformation
- Supported Builder Pattern
- How to use it in Kotlin
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);
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 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);
Assign a default value in case of missing field in the source object:
Assign a default value in case of 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 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 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 off a lambda transformation function that 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 defined on a specific field. This means that once the FieldTransformer function will be executed the field value has already been transformed.
Builder supported patterns
The library support the transformation of Java Bean using the following Builder patterns:
Standard pattern:
public class ItemType {
private final Class<?> objectClass;
private final Class<?> genericClass;
ItemType(final Class<?> objectClass, final Class<?> genericClass) {
this.objectClass = objectClass;
this.genericClass = genericClass;
}
public static ItemTypeBuilder builder() {
return new ItemType.ItemTypeBuilder();
}
// getter methods
public static class ItemTypeBuilder {
private Class<?> objectClass;
private Class<?> genericClass;
ItemTypeBuilder() {
}
public ItemTypeBuilder objectClass(final Class<?> objectClass) {
this.objectClass = objectClass;
return this;
}
public ItemTypeBuilder genericClass(final Class<?> genericClass) {
this.genericClass = genericClass;
return this;
}
public com.hotels.transformer.model.ItemType build() {
return new ItemType(this.objectClass, this.genericClass);
}
}
}
Custom Builder pattern:
To enable the transformation of Java Beans using the following Builder pattern:
public class ItemType {
private final Class<?> objectClass;
private final Class<?> genericClass;
ItemType(final ItemTypeBuilder builder) {
this.objectClass = builder.objectClass;
this.genericClass = builder.genericClass;
}
public static ItemTypeBuilder builder() {
return new ItemType.ItemTypeBuilder();
}
// getter methods
public static class ItemTypeBuilder {
private Class<?> objectClass;
private Class<?> genericClass;
ItemTypeBuilder() {
}
public ItemTypeBuilder objectClass(final Class<?> objectClass) {
this.objectClass = objectClass;
return this;
}
public ItemTypeBuilder genericClass(final Class<?> genericClass) {
this.genericClass = genericClass;
return this;
}
public com.hotels.transformer.model.ItemType build() {
return new ItemType(this);
}
}
}
It's needed to enable the custom Builder Transformation as following:
ToBean toBean = new BeanTransformer()
.setCustomBuilderTransformationEnabled(true)
.transform(sourceObject, ToBean.class);
Constraints:
- the class's fields that have to be copied must not be static
More sample beans can be found in the test package: com.hotels.beans.sample
Third-party library comparison
Following a comparison between the BULL functionalities and the following Third-Party libraries:
| BULL | Apache Bean Utils | Jackson | Dozer | |
|---|---|---|---|---|
| Mutable bean copy | X | X | X | X+ |
| Mutable bean with nested objects | X | - | X | X+ |
| Mutable bean extending classes | X | - | X | X+ |
| Immutable bean copy | X | - | - | X* |
| Mixed bean copy | X | - | - | X+ |
| Copy of beans without getter and setter methods defined | X | - | - | - |
| Mutable Bean with different field's name | X | - | - | X+ |
| Mixed with different field's type | X | - | - | X+ |
| Immutable with different field's type | X | - | - | X+ |
| Mutable Bean containing collection type fields containing complex objects | X | - | X | X |
| Mixed Bean containing collection type fields containing complex objects | X | - | - | X+ |
| Immutable Bean containing collection type fields containing complex objects | X | - | - | X+ |
Mutable Bean containing containing Map type fields with nested Maps inside. e.g. Map<String, Map<String, Integer>> |
X | - | X | X |
Mixed Bean containing containing Map type fields with nested Maps inside. e.g. Map<String, Map<String, Integer>> |
X | - | - | X+ |
Immutable Bean containing containing Map type fields with nested Maps inside. e.g. Map<String, Map<String, Integer>> |
X | - | - | X+ |
| Annotation field validation | X | - | X | - |
[*] Immutable types are not supported by Dozer. When a type doesn't have a no-arg constructor and all fields are final, Dozer can't perform the mapping. A workaround is introducing the Builder Pattern. An example can be found here [+] Requires a custom configuration
Performance
Let's have a look at the performance library performance. The test has been executed on the following objects:
- Mutable objects
- Mutable objects extending another mutable object
- Immutable objects
- Immutable objects extending another immutable object
- Mixed objects
| Mutable | Immutable | Mixed | |
|---|---|---|---|
| Simple objects (without nested objects) | ~0.011ms | ~0.018ms | NA |
| Complex objects (containing several nested object and several items in Map and Array objects) | ~0.37ms | ~0.21ms | ~0.22ms |
| CPU/Heap usage | ~0.2%/35 MB | ~0.2%/30 MB | ~0.2%/25 MB |
Transformation time screenshot
Real case testing
The Bean Utils library has been tested on a real case scenario integrating it into a real edge service (called BPE). The purpose was to compare the latency introduced by the library plus the memory/CPU usage. The dashboard's screenshot shows the latency of the invoked downstream service (called BPAS) and the one where the library has been installed (BPE). Following the obtained results:
| Classic transformer | BeanUtils library | |
|---|---|---|
| Throughput per second | 60 | 60 |
| Average CPU usage | 0.3% | 0.3% |
| Min/Max Heap Memory Usage (MB) | 90/320 | 90/320 |
| Average Latency than the downstream service | +2ms | +2ms |
| JVM stats screenshot | screenshot | screenshot |
| Dashboard screenshot | screenshot | screenshot |
Validation samples
Validate a java bean has never been so simple. The library offers different API related to this, following some examples:
Validate a Java Bean:
Given the following bean:
public class SampleBean {
@NotNull
private BigInteger id;
private String name;
// constructor
// getters and setters...
}
an instance of the above object:
SampleBean sampleBean = new SampleBean();
And one line code as:
beanUtils.getValidator().validate(sampleBean);
this will throw an InvalidBeanException as the id field is null.
Retrieve the violated constraints:
Given the following bean:
public class SampleBean {
@NotNull
private BigInteger id;
private String name;
// constructor
// getters and setters...
}
an instance of the above object:
SampleBean sampleBean = new SampleBean();
And one line code as:
List<String> violatedConstraints = beanUtils.getValidator().getConstraintViolationsMessages(sampleBean);
this will returns a list containing a constraint validation message for the id field as it's null and the constraint: @NotNull is not met.
in case it's needed to have the ConstraintViolation object:
Set<ConstraintViolation<Object>> violatedConstraints = beanUtils.getValidator().getConstraintViolations(sampleBean);
Primitive type object converter
Converts a given primitive value into the given primitive type. The supported types, in which an object can be converted (from / to), are:
Byte,byteorbyte[]ShortorshortIntegerorintLongorlongFloatorfloatDoubleordoubleBigDecimalBigIntegerCharacterorcharBooleanorbooleanString
Convert a String into an int:
Given the following variable:
String indexNumber = "26062019";
to convert it in an int:
Converter converter = new BeanUtils().getPrimitiveTypeConverter();
int indexNumber = converter.convertValue(indexNumber, int.class);
Obtain a conversion function that converts from char to byte:
It's possible to obtain a type conversion function, reusable several times in different places. Assuming that the required conversion is from char to `byte
char c = '1';
the conversion function is retrieved through:
Converter converter = new BeanUtils().getPrimitiveTypeConverter();
Optional<Function<Object, Object>> conversionFunction = converter.getConversionFunction(char.class, byte.class);
byte converted = conversionFunction.map(processor -> processor.apply(c)).orElse(0);
- in case the conversion is not needed as the primitive type and the destination type are the same it will return an empty
Optional - in case the conversion function is unavailable or no not possible the method throws a:
TypeConversionException
Map transformation samples
Samples on how to transform a Map and all others function applicable to it can be viewed here
Documentation
Detailed project documentation is available here, including some samples for testing the library inside your project.
An article that explains how it works, with suggestion and examples is available on DZone: How to Transform Any Type of Java Bean With BULL
Credits
Created by: Fabio Borriello with the contribution of: Patrizio Munzi, Andrea Marsiglia, Giorgio Delle Grottaglie & the Hotels.com's Checkout team in Rome.
The application's logo has been designed by Rob Light.
Related articles
- DZone: How to Transform Any Type of Java Bean With BULL
- InfoQ: How Expedia Is Getting Rid of Java Bean Transformers [EN] [PT-BR]
Release
All the instructions for releasing a new version are available at RELEASES.md
Badge your project
Add the following snippet in your Markdown file:
[](https://github.com/HotelsDotCom/bull)
Support
For any question, proposal, or help, please refer to the slack channel: #bull.
Legal
This project is available under the Apache 2.0 License.
Copyright 2018-2019 Expedia Inc.
