I am using Spring version 4.3.3 and Jackson version 2.8.3. I am trying to filter out specific fields from an entity bean based on some custom logic that is determined at runtime. The #JsonFilter seems ideal for this type of functionality. The problem is that when I put it at the field or method level, my custom filter never gets invoked. If I put it at the class level, it gets invoked just fine. I don't want to use it at the class level though since then I would need to separately maintain the list of hardcoded field names that I want to apply the logic to. As of Jackson 2.3, the ability to put this annotation at the field level is supposed to exist.
Here is the most basic custom filter without any custom logic yet:
public class MyFilter extends SimpleBeanPropertyFilter {
#Override
protected boolean include(BeanPropertyWriter beanPropertyWriter) {
return true;
}
#Override
protected boolean include(PropertyWriter propertyWriter) {
return true;
}
}
Then I have the Jackson ObjectMapper configuration:
public class MyObjectMapper extends ObjectMapper {
public MyObjectMapper () {
SimpleFilterProvider filterProvider = new SimpleFilterProvider();
filterProvider.addFilter("myFilter", new MyFilter());
setFilterProvider(filterProvider);
}
}
Then finally I have my entity bean:
#Entity
public class Project implements Serializable {
private Long id;
private Long version;
#JsonFilter("myFilter") private String name;
#JsonFilter("myFilter") private String description;
// getters and setters
}
If I move the #JsonFilter annotation to the class level where #Entity is, the filter at least gets invoked, but when it is at the field level like in the example here, it never gets invoked.
I have the same need but after examining the unit tests I discovered that this is not the use-case covered by annotating a field.
Annotating a field invokes a filter on the value of the field not the instance containing the field. For example, imagine you have to classes, A and B, where A contains a field of type B.
class A {
#JsonFilter("myFilter") B foo;
}
Jackson applies "myFilter" to the fields in B not in A. Since your example contains fields of type String, which has no fields, Jackson never invokes your filter.
I have a need to exclude certain fields based on the caller's permissions. For example, an employee's profile may contain his taxpayer id, which is considered sensitive information and should only be serialized if the caller is a member of the Payrole department. Since I'm using Spring Security, I wish to integrate Jackson with the current security context.
public class EmployeeProfile {
private String givenName;
private String surname;
private String emailAddress;
#VisibleWhen("hasRole('PayroleSpecialist')")
private String taxpayerId;
}
The most obvious way to do this is to Jackson's filter mechanism but it has a few limitations:
Jackson does not support nested filters so adding an access filter prohibits using filters for any other purpose.
One cannot add Jackson annotations to existing, third-party classes.
Jackson filters are not designed to be generic. The intent is to write a custom filter for each class you wish to apply filtering. For example, I you need to filter classes A and B, then you have to write an AFilter and a BFilter.
For my use-case, the solution is to use a custom annotation introspector in conjunction with a chaining filter.
public class VisibilityAnnotationIntrospector extends JacksonAnnotationIntrospector {
private static final long serialVersionUID = 1L;
#Override
public Object findFilterId(Annotated a) {
Object result = super.findFilterId(a);
if (null != result) return result;
// By always returning a value, we cause Jackson to query the filter provider.
// A more sophisticated solution will introspect the annotated class and only
// return a value if the class contains annotated properties.
return a instanceof AnnotatedClass ? VisibilityFilterProvider.FILTER_ID : null;
}
}
This is basically a copy SimpleBeanProvider that replaces calls to include with calls to isVisible. I'll probably update this to use a Java 8 BiPredicate to make the solution more general but works for now.
This class also takes another filter as an argument and will delegate to it the final decision on whether to serialize the field if the field is visible.
public class AuthorizationFilter extends SimpleBeanPropertyFilter {
private final PropertyFilter antecedent;
public AuthorizationFilter() {
this(null);
}
public AuthorizationFilter(final PropertyFilter filter) {
this.antecedent = null != filter ? filter : serializeAll();
}
#Deprecated
#Override
public void serializeAsField(Object bean, JsonGenerator jgen, SerializerProvider provider, BeanPropertyWriter writer) throws Exception {
if (isVisible(bean, writer)) {
this.antecedent.serializeAsField(bean, jgen, provider, writer);
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(bean, jgen, provider);
}
}
#Override
public void serializeAsField(Object pojo, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer) throws Exception {
if (isVisible(pojo, writer)) {
this.antecedent.serializeAsField(pojo, jgen, provider, writer);
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(pojo, jgen, provider);
}
}
#Override
public void serializeAsElement(Object elementValue, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer) throws Exception {
if (isVisible(elementValue, writer)) {
this.antecedent.serializeAsElement(elementValue, jgen, provider, writer);
}
}
private static boolean isVisible(Object pojo, PropertyWriter writer) {
// Code to determine if the field should be serialized.
}
}
I then add a custom filter provider to each instance of ObjectMapper.
#SuppressWarnings("deprecation")
public class VisibilityFilterProvider extends SimpleFilterProvider {
private static final long serialVersionUID = 1L;
static final String FILTER_ID = "dummy-filter-id";
#Override
public BeanPropertyFilter findFilter(Object filterId) {
return super.findFilter(filterId);
}
#Override
public PropertyFilter findPropertyFilter(Object filterId, Object valueToFilter) {
if (FILTER_ID.equals(filterId)) {
// This implies that the class did not have an explict filter annotation.
return new AuthorizationFilter(null);
}
// The class has an explicit filter annotation so delegate to it.
final PropertyFilter antecedent = super.findPropertyFilter(filterId, valueToFilter);
return new VisibilityPropertyFilter(antecedent);
}
}
Finally, I have a Jackson module that automatically registers the custom annotaion introspector so I don't have to add it to each ObjectMapper instance manually.
public class FieldVisibilityModule extends SimpleModule {
private static final long serialVersionUID = 1L;
public FieldVisibilityModule() {
super(PackageVersion.VERSION);
}
#Override
public void setupModule(Module.SetupContext context) {
super.setupModule(context);
// Append after other introspectors (instead of before) since
// explicit annotations should have precedence
context.appendAnnotationIntrospector(new VisibilityAnnotationIntrospector());
}
}
There are more improvements that can be made and I still have more unit tests to write (e.g., handling arrays and collections) but this is the basic strategy I used.
You can try this approach for the same purpose:
#Entity
#Inheritance(
strategy = InheritanceType.SINGLE_TABLE
)
#DiscriminatorColumn(
discriminatorType = DiscriminatorType.STRING,
length = 2
)
#Table(
name = "project"
)
#JsonTypeInfo(
use = Id.CLASS,
include = As.PROPERTY,
property = "#class"
)
#JsonSubTypes({
#Type(
value = BasicProject.class,
name = "basicProject"
),
#Type(
value = AdvanceProject.class,
name = "advanceProject"
)})
public abstract class Project {
private Long id;
private Long version;
}
#Entity
#DiscriminatorValue("AD")
public class AdvanceProject extends Project {
private String name;
private String description;
}
#Entity
#DiscriminatorValue("BS")
public class BasicProject extends Project {
private String name;
}
I don't think you will make it work. I was trying and these are results of my investigation, maybe it will be helpful.
First of all, as #Faron noticed, the #JsonFilterannotation is applied for the class being annotated not a field.
Secondly, I see things this way. Let's imagine, somewhere in Jackson internals you are able to get the actual field. You can figure out if there is the annotation using Java Reflection API. You can even get the filter name. Then you get to the filter and pass the field value there. But it happens at runtime, how will you get the corresponding JsonSerializer of the field type if you decide to serialize the field? It is impossible because of type erasure.
The only alternative I see is to forget about dynamic logic. Then you can do the following things:
1) extend JacksonAnnotationIntrospector (almost the same as implement AnnotationIntrospector but no useless default code) overriding hasIgnoreMarker method. Take a look at this answer
2) criminal starts here. Kinda weird way taking into account your initial goal but still: extend BeanSerializerModifier and filter out fields there. An example can be found here. This way you can define serializer that actually doesn't serialize anything (again, I understand how strange it is but maybe one will find it helpful)
3) similar to the approach above: define useless serializer based on BeanDescription implementing ContextualSerializer's createContextual method. The example of this magic is here
Thanks to this really good blog, I was able to use #JsonView to filter out specific fields from an entity bean based on some custom logic that is determined at runtime.
Since the #JsonFilter does not apply for the fields within a class, I found this to be a cleaner workaround.
Here is the sample code:
#Data
#AllArgsConstructor
public class TestEntity {
private String a;
#JsonView(CustomViews.SecureAccess.class)
private Date b;
#JsonView(CustomViews.SecureAccess.class)
private Integer c;
private List<String> d;
}
public class CustomViews {
public static interface GeneralAccess {}
public static interface SecureAccess {}
public static class GeneralAccessClass implements GeneralAccess {}
public static class SecureAccessClass implements SecureAccess, GeneralAccess {}
public static Class getWriterView(final boolean hasSecureAccess) {
return hasSecureAccess
? SecureAccessClass.class
: GeneralAccessClass.class;
}
}
#Test
public void test() throws JsonProcessingException {
final boolean hasSecureAccess = false; // Custom logic resolved to a boolean value at runtime.
final TestEntity testEntity = new TestEntity("1", new Date(), 2, ImmutableList.of("3", "4", "5"));
final ObjectMapper objectMapper = new ObjectMapper().enable(MapperFeature.DEFAULT_VIEW_INCLUSION);
final String serializedValue = objectMapper
.writerWithView(CustomViews.getWriterView(hasSecureAccess))
.writeValueAsString(testEntity);
Assert.assertTrue(serializedValue.contains("a"));
Assert.assertFalse(serializedValue.contains("b"));
Assert.assertFalse(serializedValue.contains("c"));
Assert.assertTrue(serializedValue.contains("d"));
}
I want to implement an annotation which registers classes (not instances of classes) with a factory as soon as the application is started. I am using Spring Framework 4.2.7.
Consider a system with a dashboard and multiple widgets. The dashboard has a configuration file which contains a list of widgets to display for the current user. When displayed it reads the configuration and creates the widgets. The widgets will receive additional parameters from the configuration.
Here is a bit of code illustrating this:
public class TestDashboard implements Dashboard {
public void dashboardPreDisplay() {
List<String> widgets = getWidgetList(/* current user in session */);
for (String widgetId : widgets) {
// create instance of DashboardWidget with given ID
DashboardWidget x = widgetFactory.createWidget(widgetId);
}
}
public List<String> getWidgetList(String user) {
// load list of IDs of DashboardWidgets to be displayed for the user
}
#Autowired
private WidgetFactory widgetFactory;
}
#Service
public class WidgetFactory {
public DashboardWidget createWidget(String widgetId) {
// look up Class<> of DashboardWidget with given id in widgetClasses
// construct and initialize DashboardWidget
}
private HashMap<String, Class<?>> widgetClasses;
}
When implementing my widgets I don't want to deal with registering the widget with the factory class. Ideally I would just annotate the widget like that:
#DashboardWidget(id = "uniqueId")
public class DashboardWidgetA implements DashboardWidget {
// ...
}
When the application starts it should scan the classpath for #DashboardWidget annotations and register the classes with the factory, so that the widgets can be constructed by giving the createWidget-method the id of the widget.
At the moment I am a little bit confused. I think Spring has every tool on board to achieve this behavior. But I cannot think of a way how to do it.
Do you have some advice for me?
Nothing prevents you to create your custom annotation:
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
public #interface DashboardWidget {}
Then you can annotate your Widget's classes and make them spring beans. You have to keep in mind if you want to have them as singletons (scope=singleton) , or separate instances per user (scope=prototype).
You have to implement:
public class WidgetInitializationListener implements ApplicationListener<ContextRefreshedEvent> {
#Override
public void onApplicationEvent(ContextRefreshedEvent event) {
ApplicationContext context = event.getApplicationContext();
String[] beanDefinitionNames = context.getBeanDefinitionNames();
for (String beanDefinitionName : beanDefinitionNames) {
String originalClassName = getOriginalClassName(beanDefinitionName, event);
if (originalClassName != null) {
Class<?> clazz = Class.forName(originalClassName);
if (hasWidgetAnnotation(clazz)) {
registerSomewhereYourWidget(context, beanDefinitionName, originalClassName);
}
}
}
}
private String getOriginalClassName(String name, ContextRefreshedEvent event) {
try {
ConfigurableListableBeanFactory factory =
(ConfigurableListableBeanFactory)event.getApplicationContext().getAutowireCapableBeanFactory();
BeanDefinition beanDefinition = factory.getBeanDefinition(name);
return beanDefinition.getBeanClassName();
} catch (NoSuchBeanDefinitionException e) {
LOG.debug("Can't get bean definition for : " + name);
return null;
}
}
So mostly here is nothing to do with spring except you just run through your beans to find annotated ones.
consider the following scenario: i have a bean that handles user-searches with a lot of parameters used on many pages with different urls. many users may spent a larger time with custom-searches and currently i am hitting the database to load those static lists everytime.
#ManagedBean
#ViewScoped
public class SearchBean extends DefaultBean {
private String searchPath; //seo: build a url-friendly path depending on search-parameters
private List<Currency>currencies;
private List<Country>countries;
private List<Market>markets;
private List<DrugTypes>drugTypes;
private List<Products>products;
/**
* ...15 other lists
*/
private List<ResultData>results;
#PostConstruct
public void init(){
this.currencies = Currency.getAll(); //jpa-entities
this.countries = Country.getAll();
this.markets = Markets.getAll();
this.drugTypes = DrugTypes.getAll();
this.products = Products.getAll();
}
public String search(){
this.results = ResultData.getByParameters(getSearchParams());
//
//e.g. localhost:8080/myApp/search/markets/germany/class-alpha-products/rhesus?faces-redirect=true
return searchPath;
}
public List<Currency> getCurrencies() { return currencies; }
public void setCurrencies(List<Currency> currencies) { this.currencies = currencies; }
public List<Country> getCountries() { return countries; }
public void setCountries(List<Country> countries) { this.countries = countries; }
public void setMarkets(List<Market> markets) { this.markets = markets; }
public List<Market> getMarkets() { return markets; }
public void setDrugTypes(List<DrugTypes> drugTypes) { this.drugTypes = drugTypes; }
public List<DrugTypes> getDrugTypes() { return drugTypes; }
public List<Products> getProducts() { return products; }
public void setProducts(List<Products> products) { this.products = products; }
}
what is the recommend way regarding to the headline? my small gripe is, that i see 20 jpa-queries on the console although the list-data which is build with <h:selectOneMenu> on client-side does not change on new pages but must be included on every subpage.
leave it as it is
put all those lists as session-attributes and remove them in #predestroy when user leaves.
put the whole bean as sessionbean (i already have 2 session-beans ("user" and "language" and i read that having more is not a good design)
store the list-data as a json-string in a cookie and recreate the list if the cookie exists?
other suggestions?
thanks for watching!
None of all. Caching DB entities isn't the responsibility of a front end (UI) framework. That's the responsibility of the persistence (DB) framework, which is thus JPA in your case.
JPA offers 2nd level caching possibilities. Main advantage as compared to all your proposals is that it knows precisely which entities are more queried and thus need to be cached, and when exactly to invalidate a cached entity because of an entity change. JSF as being a dumb HTML form based MVC framework which only delegates user interface events/data to business services knows nothing of this all.
See also:
How to configure L2 cache in Hibernate/JPA2?
Hibernate 5.1 User Guide - Chapter 12: Caching
EclipseLink Wiki - Examples / JPA / Caching
I have a number of classes, POJO style, that shares a single functionality, say readCSV method. So I want to use a single parent (or maybe abstract, not sure if it should be) class that these POJOs can extend. Here's a pseudo-code:
(abstract) class CSVUtil {
private String[] fileHeader = null;
protected void setFileHeader(fileHeader) {
this.fileHeader = fileHeader;
}
protected List<WhateverChildClass> readCSV(String fileName) {
// read CSV using Apache Commons CSV
// and return a List of child type
List<WhateverChildClass> list = null;
// some declarations
try {
list = new ArrayList<WhateverChildClass>();
csvParser = new CSVParser(fileReader, csvFormat);
List csvRecords = csvParser.getRecords();
for (...) {
CSVRecord record = (CSVRecord) csvRecords.get(i);
WhateverChildClass childClass = new WhateverChildClass();
// loop through fields of childClass using reflection and assign
for (// all fields of childClass) {
childClass.setWhateverField(record.get(fileHeader[i]));
}
list.add(childClass);
System.out.println(p);
ps.add(p);
}
}
...
return list;
}
}
on one of the child classes, say ChildA
class ChildA extends CSVUtil {
// fields, getters, setters
}
How do I code the CSVUtil such that I can determine in runtime the child class in readCSV defined in the parent class?
Is it possible to make this method static and still be inherited?
As an alternative, is there API in Apache Commons CSV that can generally read a CSV, determine its schema, and wrap it as a generic Object (I don't know if I make sense here), and return a list of whatever that Object is ?
You want that readCSV to be a static method ?
Then, i would say that ChildA class shouldn't inherit from CSVUtil, but implement an Interface ... something like that :
public final class CSVUtil {
private CSVUtil() {
}
public static <T extends ICSV> List<T> readCSV(String filename) {
...
}
class ChildA implements ICSV
In JavaFX I want to check if a checkbox is selected and I want to do this using the lookup(#id) method. However this method returns a Node, which doesn't have the isSelected() method.
The code below shows the GUIController and a class Visualize it calls, where the status of the checkbox is read. I added a solution (reading the checkbox properties in GUIController and passing them to Visualize), but this is not how I want to proceed. I whish that the checkbox status is read in Visualize, because there will be many other GUI elements that I need to read so it is more compact to pass on a single object to Visualize instead of a list precomputed in GUIController.
Thank you for suggestions!
GUI Controller:
public class GUIController implements Initializable {
#FXML private AnchorPane RootPane;
#FXML private CheckBox TextCheckBox;
#Override
public void initialize(URL url, ResourceBundle rb) {
Boolean TextCheckBoxSelected = TextCheckBox.isSelected();
Visualize visualizeInstance = new Visualize();
root3D = visualizeInstance.draw(RootPane, TextCheckBoxSelected);
/* ... */
Class called by GUIController:
public class Visualize {
public Visualize() {
//
}
public Group draw(AnchorPane RootPane, Boolean TextCheckBoxSelected) {
System.out.println(RootPane.lookup("#TextCheckBox"));
System.out.println(TextCheckBoxSelected);
/* ... */
Output:
CheckBox[id=TextCheckBox, styleClass=check-box]'Text'
true
If you really want to do it this way, just downcast the result of the lookup:
public class Visualize {
// ...
public Group draw(AnchorPane rootPane) {
CheckBox textCheckBox = (CheckBox) rootPane.lookup("#TextCheckBox");
boolean selected = textCheckBox.isSelected();
// ...
}
}
If you are doing this because you need your Visualize object to respond to changes in the CheckBox's selected state, then consider passing a BooleanProperty instead, which you can observe if you need:
public class Visualize {
private BooleanProperty selectedProperty ;
public Visualize(BooleanProperty selectedProperty) {
this.selectedProperty = selectedProperty ;
// ...
}
// ...
public Group draw() {
boolean selected = selectedProperty.get();
// ...
}
}
and
Visualize visualizeInstance = new Visualize(textCheckBox.selectedProperty());
root3D = visualizeInstance.draw();