An alternative API for filtering data with Spring MVC & Spring Data JPA.
A thorough introduction and the original rationale behind this component can be found my blog: http://blog.kaczmarzyk.net/2014/03/23/alternative-api-for-filtering-data-with-spring-mvc-and-spring-data/. In this file you can find a summary of all the current features and some API examples.
You can also take a look on a working Spring Boot app that uses this library: https://github.com/tkaczmarzyk/specification-arg-resolver-example.
The following HTTP request:
GET http://myhost/api/customers?firstName=Homer
can be handled with the following controller method:
@RequestMapping(value = "/customers", params = "firstName")
public Iterable<Customer> findByFirstName(
@Spec(path = "firstName", spec = Like.class) Specification<Customer> spec) {
return customerRepo.findAll(spec);
}which will result in the following JPA query:
select c from Customer c where c.firstName like '%Homer%'Alternatively you can annotate an interface:
@Spec(path="firstName", params="name", spec=Like.class)
public interface NameSpec extends Specification<Customer> {
}and then use it as a controller parameter without any further annotations.
All you need to do is to wire SpecificationArgumentResolver into your application. Then you can use @Spec and other annotations in your controllers. SpecificationArgumentResolver implements Spring's HandlerMethodArgumentResolver and can be plugged in as follows:
@Configuration
@EnableJpaRepositories
public class MyConfig extends WebMvcConfigurerAdapter {
@Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
argumentResolvers.add(new SpecificationArgumentResolver());
}
...
}Converter converts http parameter to object via Jackson. And you can determine your converting logic by passing your custom Converter into SpecificationArgumentResolver:
ObjectMapper myMapper = new ObjectMapper();
myMapper.registerModule(new com.fasterxml.jackson.datatype.jsr310.JavaTimeModule());
new SpecificationArgumentResolver(new Converter(myMapper));and then @Spec now supports JSR310 conversion, ex: java.time.LocalDate, java.time.LocalDateTime...
Use @com.fasterxml.jackson.annotation.JsonSubTypes to indicate the specify type of field, and it will be used by Converter to do the converting. It will help to get the correct java type, especially generic fields in super class.
We somethings declare id field in super class as generic type.
@MappedSuperclass
public abstract class Generic<ID extends Serializable> {
@Id
@GeneratedValue
private ID id;
}But generic type can not be recognized correctly in runtime, therefore we have to indicate the type.
@Entity
public class MyEntity extends Generic<Long>{
@JsonSubTypes(@Type(Long.class))
public Long getId() {
return super.getId();
}
// more fields
}It will try to find @JsonSubTypes on getter methods first, and then fields.
Use @Spec annotation to automatically resolve a Specification argument of your controller method. @Spec has path property that should be used to specify property path of the attribute of an entity, e.g. address.city. By default it's also the name of the expected HTTP parameter, e.g. GET http://myhost?address.city=Springfield.
Use spec attribute of the annotation to specify one of the following strategies for filtering.
Filters using JPAQL like expression. It adds a wildcard % at the beginning and the end of the actual value, e.g. (..) where firstName like %Homer%.
Usage: @Spec(path="firstName", spec=Like.class).
Works as Like, but the query is also case-insensitive.
Usage: @Spec(path="firstName", spec=LikeIgnoreCase.class).
Compares an attribute of an entity with the value of a HTTP parameter (exact match). E.g. (..) where gender = FEMALE.
Supports multiple data types: numbers, booleans, strings, dates, enums.
Usage: @Spec(path="gender", spec=Enum.class).
The default date format used for temporal fields is yyyy-MM-dd. It can be overriden with a configuration parameter (see LessThan below).
Works as Equal, but the query is also case-insensitive.
Compares an attribute of an entity with multiple values of a HTTP parameter. E.g. (..) where gender in (MALE, FEMALE).
HTTP request example:
GET http://myhost/customers?gender=MALE&gender=FEMALE
Supports multiple data types: numbers, booleans, strings, dates, enums.
Usage: @Spec(path="gender", spec=In.class).
The default date format used for temporal fields is yyyy-MM-dd. It can be overriden with a configuration parameter (see LessThan below).
Filters using is null or is not null, depending on the value of the parameter passed in. A value of true will filter for is null, and a value of false will filter for is not null.
The data type of the field specified in path can be anything, but the HTTP parameter must be a Boolean. You should use params attribute to make it clear that the parameter is filtering for null values.
Usage: @Spec(path="activationDate", params="activationDateNull" spec=Null.class).
If you want the query to be static, i.e. not depend on any HTTP param, use constVal attribute of Spec annotation:
For example @Spec(path="nickname", spec=Null.class, constVal="true") will always add nickname is null to the query.
Filters using a comparison operator (>, >=, < or <=). Supports multiple field types: strings, numbers, booleans, enums, dates. Field types must be Comparable (e.g, implement the Comparable interface); this is a JPA constraint.
Usage: @Spec(path="creationDate", spec=LessThan.class).
For temporal values, the default date format is yyyy-MM-dd. You can override it by providing a config value to the annotation: @Spec(path="creationDate", spec=LessThan.class, config="dd-MM-yyyy").
NOTE: comparisons are dependent on the underlying database.
- Comparisons of floats and doubles (especially floats) may be incorrect due to precision loss.
- Comparisons of booleans may be dependent on the underlying database representation.
- Comparisons of enums will be of their ordinal or string representations, depending on what you specified to JPA, e.g.,
@Enumerated(EnumType.STRING),@Enumerated(EnumType.ORDINAL)or the default (@Enumerated(EnumType.ORDINAL))
Filters by checking if a temporal field of an entity is in the provided date range. E.g. (..) where creation date between :after and :before.
It requires 2 HTTP parameters (for lower and upper bound). You should use params attribute of the @Spec annotation, i.e.: @Spec(path="registrationDate", params={"registeredAfter","registeredBefore"}, spec=DateBetween.class). The corresponding HTTP query would be: GET http://myhost/customers?registeredAfter=2014-01-01®isteredBefore=2014-12-31.
You can configure the date pattern as with LessThan described above.
You can use @JoinFetch annotation to specify paths to perform fetch join on. For example:
@RequestMapping("/customers")
public Object findByCityFetchOrdersAndAddresses(
@JoinFetch(paths = { "orders", "addresses" })
@Spec(path="address.city", params="town", spec=Like.class) Specification<Customer> customersByCitySpec) {
return customerRepo.findAll(customersByCitySpec);
}The default join type is LEFT. You can use joinType attribute of the annotation to specify different value. You can specify multiple different joins with container annotation @Joins, for example:
@RequestMapping("/customers")
public Object findByCityFetchOrdersAndAddresses(
@Joins({
@JoinFetch(paths = "orders")
@JoinFetch(paths = "addresses", joinType = JoinType.INNER)
})
@Spec(path="address.city", params="town", spec=Like.class) Specification<Customer> customersByCitySpec) {
return customerRepo.findAll(customersByCitySpec);
}You can use join annotations with custom specification interfaces (see below).
If the HTTP parameter is not present, the resolved Specification will be null. It means no filtering at all when passed to a repository. If you want to make the parameter non-optional, you should use standard Spring MVC annotations, e.g. @RequestMapping(params={"firstName"}).
By default, the expected HTTP parameter is the same as the property path. If you want them to differ, you can use params attribute of @Spec. For example this method:
@RequestMapping("/customers")
public Object findByCity(
@Spec(path="address.city", params="town", spec=Like.class) Specification<Customer> customersByCitySpec) {
return customerRepo.findAll(customersByCitySpec);
}will handle GET http://myhost/customers?town=Springfield as select c from Customer c where city.address like '%Springfield%'.
If you don't want to bind your Specification to any HTTP parameter, you can use constVal attribute of @Spec. For example:
@Spec(path="deleted", spec=Equal.class, constVal="false")will alwas produce the following: where deleted = false. It is often convenient to combine such a static part with dynamic ones using @And or @Or described below.
If you prefer an exception being thrown if the parameter is missing in the request, you can use required attribute of @Spec. For example:
@Spec(path="role", spec=Equal.class, required=true) // defaults to falseAlternatively, provide a constVal or defaultVal, which implicitly sets this flag to false.
The default value to use as a fallback when the request parameter is not provided or has an empty value.
@Spec(path="role", spec=Equal.class, defaultVal="USER")Supplying constVal implicitly sets defaultVal to empty.
You can combine the specs described above with or & and. Remember that by default all of the HTTP params are optional. If you want to make all parts of your query required, you must state that explicitly in @RequestMapping annotation (see above).
Usage:
@RequestMapping("/customers")
public Object findByName(
@And({
@Spec(path="registrationDate", params="registeredBefore", spec=DateBefore.class),
@Spec(path="lastName", spec=Like.class)}) Specification<Customer> customerSpec) {
return customerRepo.findAll(customerSpec);
}would handle requests like GET http://myhost/customers?registeredBefore=2015-01-18&lastName=Simpson
and execute queries like: select c from Customer c where c.registrationDate < :registeredBefore and c.lastName like '%Simpson%'.
Usage:
@RequestMapping("/customers")
public Object findByName(
@Or(
@Spec(path="firstName", params="name", spec=Like.class),
@Spec(path="lastName", params="name", spec=Like.class)) Specification<Customer> customerNameSpec) {
return customerRepo.findAll(customerNameSpec);
}would handle requests like GET http://myhost/customers?name=Mo
and execute queries like: select c from Customer c where c.firstName like '%Mo%' or c.lastName like '%Mo'.
You can put multiple @And inside @Disjunction or multiple @Or inside @Conjunction. @Disjunction joins nested @And queries with 'or' operator. @Conjunction joins nested @Or queries with 'and' operator. For example:
@RequestMapping("/customers")
public Object findByFullNameAndAddress(
@Conjunction({
@Or(@Spec(path="firstName", params="name", spec=Like.class),
@Spec(path="lastName", params="name", spec=Like.class)),
@Or(@Spec(path="address.street", params="address", spec=Like.class),
@Spec(path="address.city", params="address", spec=Like.class))
}) Specification<Customer> customerSpec) {
return customerRepo.findAll(customerSpec);
}would handle requests like GET http://myhost/customers?name=Sim&address=Ever
and execute queries like select c from Customer c where (c.firstName like '%Sim%' or c.lastName like '%Sim%') and (c.address.street like '%Ever%' or c.address.city like '%Ever%').
You must use @Conjunction and @Disjunction as top level annotations (instead of regular @And and @Or) because of limitations of Java annotation syntax (it does not allow cycle in annotation references).
You can join nested @And and @Or queries with simple @Spec, for example:
@RequestMapping("/customers")
public Object findByFullNameAndAddressAndNickName(
@Conjunction(value = {
@Or(@Spec(path="firstName", params="name", spec=Like.class),
@Spec(path="lastName", params="name", spec=Like.class)),
@Or(@Spec(path="address.street", params="address", spec=Like.class),
@Spec(path="address.city", params="address", spec=Like.class))
}, and = @Spec(path="nickName", spec=Like.class) Specification<Customer> customerSpec) {
return customerRepo.findAll(customerSpec);
}@RequestMapping("/customers")
public Object findByLastNameOrGoldenByFirstName(
@Disjunction(value = {
@And({@Spec(path="golden", spec=Equal.class, constVal="true"),
@Spec(path="firstName", params="name", spec=Like.class)})
}, or = @Spec(path="lastName", params="name", spec=Like.class) Specification<Customer> customerSpec) {
return customerRepo.findAll(customerSpec);
}You can annotate a custom interface that extends Specification, eg.:
@Or({
@Spec(path="firstName", params="name", spec=Like.class),
@Spec(path="lastName", params="name", spec=Like.class)
})
public interface FullNameSpec extends Specification<Customer> {
}It can be then used as a controller parameter without further annotations, i.e.:
@RequestMapping("/customers")
@ResponseBody
public Object findByFullName(FullNameSpec spec) {
return repository.findAll(spec);
}When such parameter is additionally annotated, the both specifications (from the interface and the parameter annotations) are joined with 'and' operator. For example you can define a base interface like this:
@Spec(path="deleted", spec=Equal.class, constVal="false")
public interface NotDeletedEntitySpec<T> extends Specification<T> {}and then use it as a foundation for you controller as follows:
@RequestMapping("/customers")
@ResponseBody
public Object findNotDeletedCustomerByLastName(
@Spec(path="lastName", spec=Equal.class) NotDeletedEntitySpec<Customer> spec) {
return repository.findAll(spec);
}to execute queries such as select c from Customer c where c.deleted = false and c.lastName like %Homer%.
Consider a field age of type Integer and the following specification definition:
@Spec(path="age", spec=Equal.class)If non-numeric values is passed with the HTTP request (e.g. ?age=test), then the result list will be empty. If you want an exception to be thrown instead, use onTypeMismatch property of the Spec annotation, i.e:
@Spec(path="age", spec=Equal.class, onTypeMismatch=OnTypeMismatch.EXCEPTION)This behaviour has changed in version 0.9.0 (exception was the default value in previous ones). The default OnTypeMismatch.EMPTY_RESULT is useful when using @And or @Or and their inner specs refer to fields of different types, e.g.:
@And({
@Spec(path="firstName", params="query", spec=Equal.class),
@Spec(path="customerId", params="query", spec=Equal.class)})(assuming that firstName is String and customerId is a numeric type)
Specification argument resolver is available in the Maven Central:
<dependency>
<groupId>net.kaczmarzyk</groupId>
<artifactId>specification-arg-resolver</artifactId>
<version>0.9.0</version>
</dependency>If a new version is not yet available in the central repository, you can grab it from my private repo:
<repository>
<id>kaczmarzyk.net</id>
<url>http://repo.kaczmarzyk.net</url>
</repository>