I have tried several ways
e.g.
1.create a custom JsonSerializer, and override serialize method
#Override
public void serialize(Object value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
gen.writeString("");
}
and set the JsonSerializer to NullValueSerializer,like this:
objectMapper.getSerializerProvider().setNullValueSerializer(new NullStringSerializer());
but we can not get the Class Type from null. All null will be covert to "" , include the object.
2.if use SimpleModule
SimpleModule simpleModule = new SimpleModule("StringModule", Version.unknownVersion());
simpleModule.addSerializer(Object.class, new NullStringSerializer());
objectMapper.registerModule(simpleModule);
in the serialize method, the param value do not have any properties which is null.
from the resouce code of jackson 2.6.0 , find method serializeFields in MapSerializer.java (my object is a map) line: 545
for (Map.Entry<?,?> entry : value.entrySet()) {
Object valueElem = entry.getValue();
// First, serialize key
Object keyElem = entry.getKey();
if (keyElem == null) {
provider.findNullKeySerializer(_keyType, _property).serialize(null, gen, provider);
} else {
// One twist: is entry ignorable? If so, skip
if (ignored != null && ignored.contains(keyElem)) continue;
keySerializer.serialize(keyElem, gen, provider);
}
// And then value
if (valueElem == null) {
provider.defaultSerializeNull(gen);
} else {...}
}
when the valueElem is null, the provide just covert it to null.
and do not have any interface for me to change the strategy.
I can override MapSerializer ,but I do not know how to set the new MapSerializer to the factory.
Is there any solution?
expect your help,thank you!
find a solution :
the abstract class SerializerProvider has a method named findNullValueSerializer, which is called to get the serializer to use for serializing null values for specified property.
We can override SerializerProvider#findNullValueSerializer and match String class:
#Override
public JsonSerializer<Object> findNullValueSerializer(BeanProperty property) throws JsonMappingException {
if (property.getType().getRawClass().equals(String.class)) {
return EmptyStringSerializer.INSTANCE;
} else {
return super.findNullValueSerializer(property);
}
}
and then set SerializerProvider to our ObjectMapper instance.
done.
Related
I have a JAXB-annotated employee class:
#XmlRootElement(name = "employee")
public class Employee {
private Integer id;
private String name;
...
#XmlElement(name = "id")
public int getId() {
return this.id;
}
... // setters and getters for name, equals, hashCode, toString
}
And a JAX-RS resource object (I'm using Jersey 1.12)
#GET
#Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Path("/")
public List<Employee> findEmployees(
#QueryParam("name") String name,
#QueryParam("page") String pageNumber,
#QueryParam("pageSize") String pageSize) {
...
List<Employee> employees = employeeService.findEmployees(...);
return employees;
}
This endpoint works fine. I get
<employees>
<employee>
<id>2</id>
<name>Ana</name>
</employee>
</employees>
However, if I change the method to return a Response object, and put the employee list in the response body, like this:
#GET
#Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Path("/")
public Response findEmployees(
#QueryParam("name") String name,
#QueryParam("page") String pageNumber,
#QueryParam("pageSize") String pageSize) {
...
List<Employee> employees = employeeService.findEmployees(...);
return Response.ok().entity(employees).build();
}
the endpoint results in an HTTP 500 due to the following exception:
javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class java.util.ArrayList, and Java type class java.util.ArrayList, and MIME media type application/xml was not found
In the first case, JAX-RS has obviously arranged for the proper message writer to kick in when returning a collection. It seems somewhat inconsistent that this doesn't happen when the collection is placed in the entity body. What approach can I take to get the automatic JAXB serialization of the list to happen when returning a response?
I know that I can
Just return the list from the resource method
Create a separate EmployeeList class
but was wondering whether there is a nice way to use the Response object and get the list to serialize without creating my own wrapper class.
You can wrap the List<Employee> in an instance of GenericEntity to preserve the type information:
http://docs.oracle.com/javaee/6/api/javax/ws/rs/core/GenericEntity.html
You can use GenericEntity to send the collection in the Response. You must have included appropriate marshal/unmarshal library like moxy or jaxrs-jackson.
Below is the code :
#GET
#Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Path("/")
public Response findEmployees(
#QueryParam("name") String name,
#QueryParam("page") String pageNumber,
#QueryParam("pageSize") String pageSize) {
...
List<Employee> employees = employeeService.findEmployees(...);
GenericEntity<List<Employee>> entity = new GenericEntity<List<Employee>>(Lists.newArrayList(employees))
return Response.ok().entity(entity).build();
}
I resolved this issue by extending the default JacksonJsonProvider class, in particular method writeTo.
Analyzing the source code of this class I found the block where the actual type is instantiated by reflection, so I've modified the source code as below:
public void writeTo(Object value, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String,Object> httpHeaders, OutputStream entityStream) throws IOException {
/* 27-Feb-2009, tatu: Where can we find desired encoding? Within
* HTTP headers?
*/
ObjectMapper mapper = locateMapper(type, mediaType);
JsonEncoding enc = findEncoding(mediaType, httpHeaders);
JsonGenerator jg = mapper.getJsonFactory().createJsonGenerator(entityStream, enc);
jg.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
// Want indentation?
if (mapper.getSerializationConfig().isEnabled(SerializationConfig.Feature.INDENT_OUTPUT)) {
jg.useDefaultPrettyPrinter();
}
// 04-Mar-2010, tatu: How about type we were given? (if any)
JavaType rootType = null;
if (genericType != null && value != null) {
/* 10-Jan-2011, tatu: as per [JACKSON-456], it's not safe to just force root
* type since it prevents polymorphic type serialization. Since we really
* just need this for generics, let's only use generic type if it's truly
* generic.
*/
if (genericType.getClass() != Class.class) { // generic types are other impls of 'java.lang.reflect.Type'
/* This is still not exactly right; should root type be further
* specialized with 'value.getClass()'? Let's see how well this works before
* trying to come up with more complete solution.
*/
//**where the magic happens**
//if the type to instantiate implements collection interface (List, Set and so on...)
//Java applies Type erasure from Generic: e.g. List<BaseRealEstate> is seen as List<?> and so List<Object>, so Jackson cannot determine #JsonTypeInfo correctly
//so, in this case we must determine at runtime the right object type to set
if(Collection.class.isAssignableFrom(type))
{
Collection<?> converted = (Collection<?>) type.cast(value);
Class<?> elementClass = Object.class;
if(converted.size() > 0)
elementClass = converted.iterator().next().getClass();
//Tell the mapper to create a collection of type passed as parameter (List, Set and so on..), containing objects determined at runtime with the previous instruction
rootType = mapper.getTypeFactory().constructCollectionType((Class<? extends Collection<?>>)type, elementClass);
}
else
rootType = mapper.getTypeFactory().constructType(genericType);
/* 26-Feb-2011, tatu: To help with [JACKSON-518], we better recognize cases where
* type degenerates back into "Object.class" (as is the case with plain TypeVariable,
* for example), and not use that.
*/
if (rootType.getRawClass() == Object.class) {
rootType = null;
}
}
}
// [JACKSON-578]: Allow use of #JsonView in resource methods.
Class<?> viewToUse = null;
if (annotations != null && annotations.length > 0) {
viewToUse = _findView(mapper, annotations);
}
if (viewToUse != null) {
// TODO: change to use 'writerWithType' for 2.0 (1.9 could use, but let's defer)
ObjectWriter viewWriter = mapper.viewWriter(viewToUse);
// [JACKSON-245] Allow automatic JSONP wrapping
if (_jsonpFunctionName != null) {
viewWriter.writeValue(jg, new JSONPObject(this._jsonpFunctionName, value, rootType));
} else if (rootType != null) {
// TODO: change to use 'writerWithType' for 2.0 (1.9 could use, but let's defer)
mapper.typedWriter(rootType).withView(viewToUse).writeValue(jg, value);
} else {
viewWriter.writeValue(jg, value);
}
} else {
// [JACKSON-245] Allow automatic JSONP wrapping
if (_jsonpFunctionName != null) {
mapper.writeValue(jg, new JSONPObject(this._jsonpFunctionName, value, rootType));
} else if (rootType != null) {
// TODO: change to use 'writerWithType' for 2.0 (1.9 could use, but let's defer)
mapper.typedWriter(rootType).writeValue(jg, value);
} else {
mapper.writeValue(jg, value);
}
}
}
I am having some issues in the mapping mentioned in the title. Here are the details:
class MyDomain
{
public Iesi.Collections.Generic.ISet<SomeType> MySomeTypes{ get; set; }
....
}
class MyDTO
{
public IList<SomeTypeDTO> MySomeTypes{ get; set; }
...
}
The mapping:
Mapper.CreateMap<MyDomain, MyDTO>().ForMember(dto=>dto.MySomeTypes, opt.ResolveUsing<DomaintoDTOMySomeTypesResolver>());
Mapper.CreateMap<MyDTO, MyDomain>().ForMember(domain=>domain.MySomeTypes, opt.ResolveUsing<DTOtoDomainMySomeTypesResolver>());
The Resolvers:
class DomaintoDTOMySomeTypesResolver: ValueResolver<MyDomain, IList<SomeTypeDTO>>
{
protected override IList<SomeTypeDTO> ResolveCore(MyDomain source)
{
IList<SomeTypeDTO> abc = new List<DemandClassConfigurationDTO>();
//Do custom mapping
return abc;
}
}
class DTOtoDomainMySomeTypesResolver: ValueResolver<MyDTO, Iesi.Collections.Generic.ISet<SomeType>>
{
protected override Iesi.Collections.Generic.ISet<SomeType> ResolveCore(SystemParameterDTO source)
{
Iesi.Collections.Generic.ISet<SomeType> abc = new HashedSet<SomeType>();
//Do custom mapping
return abc;
}
}
Mapping from Domain to DTO works ok and as expected I get a MyDTO object with IList of "SomeTypeDTO" objects.
However mapping of the DTO to Domain throws the following error:
Exception of type 'AutoMapper.AutoMapperMappingException' was thrown.
----> AutoMapper.AutoMapperMappingException : Trying to map Iesi.Collections.Generic.HashedSet`1[SomeType, MyAssembly...] to Iesi.Collections.Generic.ISet`1[SomeType, MyAssembly...]
Exception of type 'AutoMapper.AutoMapperMappingException' was thrown.
----> System.InvalidCastException : Unable to cast object of type 'System.Collections.Generic.List`1[SomeType]' to type 'Iesi.Collections.Generic.ISet`1[SomeType]
What might I be doing wrong and what do the error messages imply? It almost seems that automapper is having some issues in mapping the ISet ( together with its concrete implementation HashedSet). My understanding is that in the above described scenario automapper should just use the ISet reference returned by "DTOtoDomainMySomeTypesResolver". I also don't see why I am getting the "cast from List to ISet error".
This is because AutoMapper currently doesn't support ISet<> collection properties. It works when the destination property of ISet<> is already instantiated (is not null), because the ISet<> actually inherits from ICollection<>, thus Automapper can understand that and will do the collection mapping properly.
It doesn't work when the destination property is null and is interface type. You get this error, because automapper actually found out it can be assigned from ICollection<> so it instantiates the property using generic List<>, which is default collection when automapper must create new collection property, but then when it tries to actually assign it, it will fail, because obviously List<> cannot be cast to ISet<>
There are three solution to this:
Create a feature request to support ISet<> collections and hope they will add it
Make sure the property is not null. Eg. instantiate it in constructor to empty HashSet<>. This might cause some troubles for ORM layers, but is doable
The best solution that I went with is to create custom value resolver, which you already have and instantiate the property yourself if it is null. You need to implement the IValueResolver, because the provided base ValueResolver will not let you instantiate the property. Here is the code snippet that I used:
public class EntityCollectionMerge : IValueResolver
where TDest : IEntityWithId
where TSource : IDtoWithId
{
public ResolutionResult Resolve(ResolutionResult source)
{
//if source collection is not enumerable return
var sourceCollection = source.Value as IEnumerable;
if (sourceCollection == null) return source.New(null, typeof(IEnumerable));
//if the destination collection is ISet
if (typeof(ISet).IsAssignableFrom(source.Context.DestinationType))
{
//get the destination ISet
var destSet = source.Context.PropertyMap.GetDestinationValue(source.Context.DestinationValue) as ISet;
//if destination set is null, instantiate it
if (destSet == null)
{
destSet = new HashSet();
source.Context.PropertyMap.DestinationProperty.SetValue(source.Context.DestinationValue, destSet);
}
Merge(sourceCollection, destSet);
return source.New(destSet);
}
if (typeof(ICollection).IsAssignableFrom(source.Context.DestinationType))
{
//get the destination collection
var destCollection = source.Context.PropertyMap.GetDestinationValue(source.Context.DestinationValue) as ICollection;
//if destination collection is null, instantiate it
if (destCollection == null)
{
destCollection = new List();
source.Context.PropertyMap.DestinationProperty.SetValue(source.Context.DestinationValue, destCollection);
}
Merge(sourceCollection, destCollection);
return source.New(destCollection);
}
throw new ArgumentException("Only ISet and ICollection are supported at the moment.");
}
public static void Merge(IEnumerable source, ICollection destination)
{
if (source == null) return;
var destinationIds = destination.Select(x => x.Id).ToHashSet();
var sourceDtos = source.ToDictionary(x => x.Id);
//add new or update
foreach (var sourceDto in sourceDtos)
{
//if the source doesnt exist in destionation add it
if (sourceDto.Key (sourceDto.Value));
continue;
}
//update exisiting one
Mapper.Map(sourceDto.Value, destination.First(x => x.Id == sourceDto.Key));
}
//delete entity in destination which were removed from source dto
foreach (var entityToDelete in destination.Where(entity => !sourceDtos.ContainsKey(entity.Id)).ToList())
{
destination.Remove(entityToDelete);
}
}
}
Then on your mapping use opt => opt.ResolveUsing(new EntitCollectionMerge<Entity,Dto>()).FromMember(x => x.ISetMember) or if you have lots of collection like this you can add them automatically to all of them via typeMaps.
I have a Spring3 controller in which I'm using the #RequestMapping annotation. I know I can use the params value to route based on the the presence or lack of a url parameter, but is there a way to route based on the presence of one of two parameters?
Ideally I'd have something like the following:
#RequestMapping(value="/auth", params="error OR problem")
public ModelAndView errorInAuthenticate()
Where I route to errorInAuthenticate if the parameters error OR problem exist.
Unfortunately #RequestMapping params are combined using AND, not OR. (Source)
simply map both params as not required and test them:
#RequestMapping(value="/auth")
public ModelAndView errorInAuthenticate(#RequestParam(value="error", required=false) String errorParam,
#RequestParam(value="problem", required=false) String problemParam) {
if(errorParam != null || problemParam != null) {
//redirect
}
}
You can do it using Spring AOP and create a surrounding aspect for that request mapping.
Create an annotation like the following:
public #interface RequestParameterOrValidation{
String[] value() default {};
}
Then you can annotate your request mapping method with it:
#GetMapping("/test")
#RequestParameterOrValidation(value={"a", "b"})
public void test(
#RequestParam(value = "a", required = false) String a,
#RequestParam(value = "b", required = false) String b) {
// API code goes here...
}
Create an aspect around the annotation. Something like:
#Aspect
#Component
public class RequestParameterOrValidationAspect {
#Around("#annotation(x.y.z.RequestParameterOrValidation) && execution(public * *(..))")
public Object time(final ProceedingJoinPoint joinPoint) throws Throwable {
Object[] args= joinPoint.getArgs();
MethodSignature methodSignature = (MethodSignature) thisJoinPoint.getStaticPart().getSignature();
Method method = methodSignature.getMethod();
Annotation[][] parameterAnnotations = method.getParameterAnnotations();
RequestParameterOrValidation requestParamsOrValidation= method.getAnnotation(RequestParameterOrValidation.class);
String[] params=requestParamsOrValidation.value();
boolean isValid=false;
for (int argIndex = 0; argIndex < args.length; argIndex++) {
for (Annotation annotation : parameterAnnotations[argIndex]) {
if (!(annotation instanceof RequestParam))
continue;
RequestParam requestParam = (RequestParam) annotation;
if (Arrays.stream(params).anyMatch(requestParam.value()::equals) && args[argIndex]!=null) {
// Atleast one request param exist so its a valid value
return joinPoint.proceed();
}
}
}
throw new IllegalArgumentException("illegal request");
}
}
Note:- that it would be a good option to return 400 BAD REQUEST here since the request was not valid. Depends on the context, of course, but this is a general rule of thumb to start with.
Is there any way to check declaratively whether an enum has a specified value. For example:
<h:graphicImage name="error.png" library="images"
rendered="#{viewController.current.status == Status.ERROR}" />
It's a little bit tedious to define a method in the managed beand that checks this for every enum value, e.g.
public boolean isStateIsError() {
return current.getStatus() == Status.ERROR;
}
Is there a shorter/better way of doing this?
Until EL 3.0 it's not possible to import enums in EL scope. You can however just treat and compare them like strings, i.e. the enum constant value must be quoted like below.
<h:graphicImage name="error.png" library="images"
rendered="#{viewController.current.status eq 'ERROR'}" />
I know this question is a bit older now, but i had the same problem and found another solution, which i want to share :
Create a Custom EL-Resolver and use enums and java constants as objects in jsf el:
<h:graphicImage name="error.png" library="images"
rendered="#{viewController.current.status == Status.ERROR}" />
But before you can use enums this way you have to do 3 steps.
1. step - Copy this Class and replace "MY_ENUM" through your enumClass (in the example above it would be "Status")
public class EnumCache {
private Map<String, Object> propertCache = new HashMap<String, Object>();
private Map<String, Class> baseCache = new HashMap<String, Class>();
private static EnumCache staticEnumCache = null;
public static EnumCache instance() {
if (staticEnumCache == null) { staticEnumCache = new EnumCache(); }
return staticEnumCache;
}
private EnumCache() {
List<Class<?>> classes = new ArrayList<Class<?>>();
classes.add(MY_ENUM.class);
for(Class clazz : classes) {
try {
baseCache.put(clazz.getSimpleName(), clazz);
Method m = clazz.getMethod("values", (Class[]) null);
Enum<?>[] valueList = (Enum[]) m.invoke(null, (Object[]) null);
for (Enum<?> en : valueList) {
propertCache.put(clazz.getSimpleName() + "." + en.name(), en);
}
} catch (Exception e) {
System.err.println(clazz.getSimpleName(), e);
}
}
}
public Object getValueForKey(String key) {
return propertCache.get(key);
}
public Class getClassForKey(String key) {
return baseCache.get(key);
}
}
2. step - add this EnumResolver - This class will map your JSF expression to the enum in cache (step 1)
public class MyEnumResolver extends ELResolver {
public Object getValue(ELContext context, Object base, Object property) {
Object result = null;
if (base == null) {
result = EnumCache.instance().getClassForKey(property + "");
} else if (base instanceof Class) {
result = EnumCache.instance().getValueForKey(((Class) base).getSimpleName() + "." + property);
}
if (result != null) {
context.setPropertyResolved(true);
}
return result;
}
public Class<?> getCommonPropertyType(ELContext context, Object base) {
return null;
}
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
return null;
}
public Class<?> getType(ELContext context, Object base, Object property) {
return null;
}
public boolean isReadOnly(ELContext context, Object base, Object property) {
return false;
}
public void setValue(ELContext context, Object base, Object property, Object arg3) {
}
}
3. step - register the EnumResolver in faces-config.xml
<faces-config>
<application>
<el-resolver>com.asd.MyEnumResolver</el-resolver>
</application>
</faces-config>
NOTE:
If you want to access your java constants this way, you just have to extend the constructor of the enumCache class.
This (untestet) example should work:
baseCache.put(CLASS_WITH_CONSTANTS.getSimpleName(), clazz);
for (Field field : CLASS_WITH_CONSTANTS.getDeclaredFields()) {
try {
propertCache.put(CLASS_WITH_CONSTANTS.getSimpleName() + "."
+ field.getName(), field.get(null));
} catch (Exception e) { }
}
Hope this reduced but working code can help anybody.
Update
I see this benefits:
If you use strings in jsf (viewController.current.status == 'ERROR_abcdefg'), you can misspell the value and wont recognise it so fast.
With my solution you would get an error while loading the jsf file, because the enum could not be resolved.
You can see in the sourcecode that "ERROR" is value of the enum "STATUS".
When you compare two values in el, the class of the enums will be compared too.
So for example PersonState.ACTIV is not the same like AccounState.ACTIV.
When i have to change my enum value from PersonState.ACTIV to PersonState.ACTIVATED i can search for the String "PersonState.ACTIV" in my sourcecode. searching for "ACTIV" would have much more matches.
I solved a similar problem by statically dumping all the enum keys (which are used in the rendered UI components) in a map and then I use a static getByKey method to convert the value from the UI into an actual native enum in the setter, throwing an Exception if the value provided is invalid:
public enum ReportType {
FILING("F", "Filings"),
RESOLUTION("R", "Resolutions"),
BASIS("B", "Bases"),
STAFF("T", "Staff Counts"),
COUNTS("I", "Counts");
private String key;
private String label;
private static Map<String, ReportType> keyMap = new HashMap<String, ReportType>();
static {
for(ReportType type : ReportType.values()) {
keyMap.put(type.getKey(), type);
}
}
private ReportType(String _key, String _label) {
this.key = _key;
this.label = _label;
}
public String getKey() {
return this.key;
}
public String getLabel() {
return this.label;
}
public static List<ReportType> getValueList() {
return Arrays.asList(ReportType.values());
}
public static ReportType getByKey(String _key) {
ReportType result = keyMap.get(_key);
if(result == null) {
throw new IllegalArgumentException("Invalid report type key: " + _key);
}
return result;
}
}
In the UI tier, the enum key is used as the value and the enum label is used as the label:
<f:selectItems var="rptTypeItem" value="#{reportController.allReportTypes}"
itemLabel="#{rptTypeItem.label}" itemValue="#{rptTypeItem.key}"/>
In the managed bean, I convert the enum into a renderable list, using the getValueList() from the enum:
public List<ReportType> getAllReportTypes() {
return ReportType.getValueList();
}
Finally, the [g|s]etters in the managed bean look as follows:
public String getReportType() {
return this.crtRptType.getKey();
}
public void setReportType(String _val) {
this.crtRptType = ReportType.getByKey(_val);
}
I think it could be done it the following way:
Create a method in you bean that would return the list of enums, for example
public Status[] getStatuses() {
Status.values();
}
then you can use the enum in EL like this
<h:graphicImage name="error.png" library="images"
rendered="#{viewController.current.status == someBean.statuses[0]}" />
assuming that the order of enum members is not going to be changed (for ex. here statuses[0] is ERROR). However, I would fix the positions like this:
public Status[] getStatuses() {
Status myStatuses = new Status [2]; // or whatever number of statuses you are going to use in UI
myStatuses [0] = Status.ERROR;
myStatuses [1] = Status.RUNNING;
return myStatuses;
}
This is still not dynamic solution, but it's better than hard-coding in EL. Might be especially useful when you'r using localization for you statuses (enum values depending on locale/translation).
Using Automapper, what is the best way to setup a global convention such that all System.Uri properties are converted to a string that represents the AbsoluteUri property?
Ideally, I'd like to have a null System.Uri resolve to a value of String.Empty rather than null.
Setup the map:
Mapper.CreateMap<System.Uri, string>().ConvertUsing<UriToStringConverter>();
Create the TypeConverter class:
public class UriToStringConverter : ITypeConverter<System.Uri, string>
{
public string Convert(ResolutionContext context)
{
if (context.SourceValue == null)
{
return String.Empty;
}
return ((System.Uri)context.SourceValue).AbsoluteUri;
}
}