I need to pass some field values from one jsp to another jsp using Struts2 and action classes. Can any one suggest me the best way to do it. How to pass values using SessionAware interface?
Implement SessionAware interface and unimplemented methods. After this you just need to add parameter in Map. The Map will contain all session variable vales as Key value pair. you can add, remove values from Map.
Here is a Example of Action Class
public class SampleForm implements SessionAware{
//Fields that hold data
private String Welcome1="";
// This Map will contain vales in Session
private Map session;
public String execute() throws Exception {
return SUCCESS;
}
public void setWelcome1(String s) {
this.Welcome1= s;
}
public String getWelcome1() {
return Welcome1;
}
public void setSession(Map session) {
this.session = session;
}
public Map getSession() {
return session;
}
}
If you implement SessionAware then your actions will receive a Map containing the session variables. If one action puts a value into the map:
session.put("username", "Newbie");
then later actions can retrieve that value from the map:
String username = session.get("username");
Related
I have a method that fetches all the data and i am caching the result of that method but i am not able to evict the result.
#Component("cacheKeyGenerator")
public class CacheKeyGenerator implements KeyGenerator {
#Override
public Object generate(Object target, Method method, Object... params) {
final List<Object> key = new ArrayList<>();
key.add(method.getDeclaringClass().getName());
return key;
}
}
CachedMethod:-
#Override
#Cacheable(value="appCache",keyGenerator="cacheKeyGenerator")
public List<Contact> showAllContacts() {
return contactRepository.findAll();
}
#Override
#CachePut(value="appCache",key="#result.id")
public Contact addData(Contact contact) {
return contactRepository.save(contact);
}
Now when ever addData is called i want the data in the cache "appCache" with the key ="cacheKeyGenerator" to be evicted.So that the data returned by the method "showAllContacts()" is accurate.Can anyone please help!
The Entire code can be found at - https://github.com/iftekharkhan09/SpringCaching
Assuming you have a known constant cache key for showAllContacts then the solution should be to simply add #CacheEvict on addData passing in the cache name and key value:
#Override
#Caching(
put = {#CachePut(value="appCache", key="#result.id")},
evict = {#CacheEvict(cacheNames="appCache", key="someConstant")}
)
public Contact addData(Contact contact) {
return contactRepository.save(contact);
}
However because you use a key generator it is a bit more involved. Now given what your key generator does, you could instead pick a value for that cache key, making sure there can't be any collisions with the values from #result.id and use that value instead of a the key generator returned one.
I just want to disable cache for users that are admins. So I write a method to generate keys as below that returns null for admins. But I get
java.lang.IllegalArgumentException: Null key returned for cache
operation
exeption.
Is there any way achieve that?
//a method that generates a menu for each user
#Cacheable(cacheNames = "topmenu", keyGenerator = "uiComponentKey")
#Override
public String renderResponse() {...}
//method used by a key generator to generate cache keys.
#Override
public Object getCacheKey() {
if (user.isAdmin()) {
return null;
}
return user.getUser().getLogin() + "#" + "topmenu";
}
I guess you can achive that using conditional caching feature. Smth like this:
#Cacheable(cacheNames = "topmenu", condition="#user.isAdmin()")
#Override
public String renderResponse(User user) {...}
Note, that you're going to have to pass user object to this method in this case.
I am wondering what is the purpose of org.springframework.beans.factory.config.Scope.resolveContextualObject(String key) and org.springframework.beans.factory.config.Scope.getConversationId()?
From the javadoc:
Object resolveContextualObject(String key)
Resolve the contextual object for the given key, if any. E.g. the HttpServletRequest object for key "request".
String getConversationId()
Return the conversation ID for the current underlying scope, if any.
The exact meaning of the conversation ID depends on the underlying storage mechanism. In the case of session-scoped objects, the conversation ID would typically be equal to (or derived from) the session ID; in the case of a custom conversation that sits within the overall session, the specific ID for the current conversation would be appropriate.
This description doesn't tell me much.
Could you give me some examples which demonstrate how to make use of these methods?
My observation is that resolveContextualObject(String key) looks like a code smell, where where a Scope can expose some internal object.
Having:
public class MyCustomScope implements Scope {
private Pair<String, String> myPair;
#Override
public Object resolveContextualObject(String key) {
if ("myKey".equals(key)) return myPair;
return null;
}
// ...
}
#Configuration
public class RegisterMyScopeConfig {
#Bean
public BeanFactoryPostProcessor beanFactoryPostProcessor() {
return beanFactory -> beanFactory.registerScope(
"mycustomscope", new MyCustomScope());
}
}
Then you can:
#Scope("mycustomscope")
#Component
class MyComponent {
#Value("#{myKey.first}")
private String firstOfMyPair;
// or
#Value("#{myKey}")
private Pair<String,String> myPair;
}
Of course the way how you resolved object which matches key, might be fancier ;).
For example, in GenericScope it looks like that:
#Override
public Object resolveContextualObject(String key) {
Expression expression = parseExpression(key);
return expression.getValue(this.evaluationContext, this.beanFactory);
}
The client periodically calls an async method (long polling), passing it a value of a stock symbol, which the server uses to query the database and return the object back to the client.
I am using Spring's DeferredResult class, however I'm not familiar with how it works. Notice how I am using the symbol property (sent from client) to query the database for new data (see below).
Perhaps there is a better approach for long polling with Spring?
How do I pass the symbol property from the method deferredResult() to processQueues()?
private final Queue<DeferredResult<String>> responseBodyQueue = new ConcurrentLinkedQueue<>();
#RequestMapping("/poll/{symbol}")
public #ResponseBody DeferredResult<String> deferredResult(#PathVariable("symbol") String symbol) {
DeferredResult<String> result = new DeferredResult<String>();
this.responseBodyQueue.add(result);
return result;
}
#Scheduled(fixedRate=2000)
public void processQueues() {
for (DeferredResult<String> result : this.responseBodyQueue) {
Quote quote = jpaStockQuoteRepository.findStock(symbol);
result.setResult(quote);
this.responseBodyQueue.remove(result);
}
}
DeferredResult in Spring 4.1.7:
Subclasses can extend this class to easily associate additional data or behavior with the DeferredResult. For example, one might want to associate the user used to create the DeferredResult by extending the class and adding an additional property for the user. In this way, the user could easily be accessed later without the need to use a data structure to do the mapping.
You can extend DeferredResult and save the symbol parameter as a class field.
static class DeferredQuote extends DeferredResult<Quote> {
private final String symbol;
public DeferredQuote(String symbol) {
this.symbol = symbol;
}
}
#RequestMapping("/poll/{symbol}")
public #ResponseBody DeferredQuote deferredResult(#PathVariable("symbol") String symbol) {
DeferredQuote result = new DeferredQuote(symbol);
responseBodyQueue.add(result);
return result;
}
#Scheduled(fixedRate = 2000)
public void processQueues() {
for (DeferredQuote result : responseBodyQueue) {
Quote quote = jpaStockQuoteRepository.findStock(result.symbol);
result.setResult(quote);
responseBodyQueue.remove(result);
}
}
I am trying to submit a form from Ext JS 4 to a Spring 3 Controller using JSON. I am using Jackson 1.9.8 for the serialization/deserialization using Spring's built-in Jackson JSON support.
I have a status field that is initially null in the Domain object for a new record. When the form is submitted it generates the following json (scaled down to a few fields)
{"id":0,"name":"someName","status":""}
After submitted the following is seen in the server log
"nested exception is org.codehaus.jackson.map.JsonMappingException: Can not construct instance of com.blah.domain.StatusEnum from String value '': value not one of the declared Enum instance names"
So it appears that Jackson is expecting a valid Enum value or no value at all including an empty string. How do I fix this whether it is in Ext JS, Jackson or Spring?
I tried to create my own ObjectMapper such as
public class MyObjectMapper extends Object Mapper {
public MyObjectMapper() {
configure(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true);
}
}
and send this as a property to MappingJacksonMappingView but this didn't work. I also tried sending it in to MappingJacksonHttpMessageConverter but that didn't work. Side question: Which one should I be sending in my own ObjectMapper?
Suggestions?
The other thing you could do is create a specialized deserializer (extends org.codehaus.jackson.map.JsonDeserializer) for your particular enum, that has default values for things that don't match. What I've done is to create an abstract deserializer for enums that takes the class it deserializes, and it speeds this process along when I run into the issue.
public abstract class EnumDeserializer<T extends Enum<T>> extends JsonDeserializer<T> {
private Class<T> enumClass;
public EnumDeserializer(final Class<T> iEnumClass) {
super();
enumClass = iEnumClass;
}
#Override
public T deserialize(final JsonParser jp,
final DeserializationContext ctxt) throws IOException, JsonProcessingException {
final String value = jp.getText();
for (final T enumValue : enumClass.getEnumConstants()) {
if (enumValue.name().equals(value)) {
return enumValue;
}
}
return null;
}
}
That's the generic class, basically just takes an enum class, iterates over the values of the enum and checks the next token to match any name. If they do it returns it otherwise return null;
Then If you have an enum MyEnum you'd make a subclass of EnumDeserializer like this:
public class MyEnumDeserializer extends EnumDeserializer<MyEnum> {
public MyEnumDeserializer() {
super(MyEnum.class);
}
}
Then wherever you declare MyEnum:
#JsonDeserialize(using = MyEnumDeserializer.class)
public enum MyEnum {
...
}
I'm not familiar with Spring, but just in case, it may be easier to handle that on the client side:
Ext.define('My.form.Field', {
extend: 'Ext.form.field.Text',
getSubmitValue: function() {
var me = this,
value;
value = me.getRawValue();
if ( value === '' ) {
return ...;
}
}
});
You can also disallow submitting empty fields by setting their allowBlank property to false.
Ended up adding defaults in the EXT JS Model so there is always a value. Was hoping that I didn't have to this but it's not that big of a deal.
I have the same issue. I am reading a JSON stream with some empty strings. I am not in control of the JSON stream, because it is from a foreign service. And I am always getting the same error message. I tried this here:
mapper.getDeserializationConfig().with(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
But without any effect. Looks like a Bug.