Develop Reference

Storing null as value of Entity Property?

Since Entity store is throwing out when storing null value, I managed to get a "hack" to save a null value into it. However I am not sure if my approach is futile.
Here's a snippet:
entityStore.executeInTransaction(new StoreTransactionalExecutable() {
#Override
public void execute(#NotNull final StoreTransaction txn) {
try {
entityStore.registerCustomPropertyType(txn, UndefinedIterable.class, UndefinedBinding.BINDING);
} catch (Exception e) {
}
final Entity entity = txn.newEntity(storeName);
Iterator<String> it = comparableMap.keySet().iterator();
while (it.hasNext()) {
String key = it.next();
Comparable value = comparableMap.get(key);
if(value == null) {
entity.setProperty(key, new UndefinedIterable());
} else {
entity.setProperty(key, value);
}
}
First question here is, is it safe to registerCustomPropertyType over and over again, since this method will be called each time the server gets a POST request.
Next is the UndefinedIterable even needed here?
Here's the complete code
UndefinedIterable.java
public class UndefinedIterable implements Serializable, ByteIterable {
private byte[] bytes;
public UndefinedIterable() {
bytes = "null".getBytes();
}
#Override
public ByteIterator iterator() {
return new ArrayByteIterable(bytes).iterator();
}
#Override
public byte[] getBytesUnsafe() {
return bytes;
}
#Override
public int getLength() {
return bytes.length;
}
#NotNull
#Override
public ByteIterable subIterable(int offset, int length) {
return null;
}
#Override
public int compareTo(#NotNull ByteIterable o) {
return 0;
}
}
UndefinedBinding.java
public class UndefinedBinding extends ComparableBinding {
public static final UndefinedBinding BINDING = new UndefinedBinding();
#Override
public Comparable readObject(#NotNull ByteArrayInputStream stream) {
try {
byte[] serialized = ByteStreams.toByteArray(stream);
Comparable deserialized = deserialize(serialized, Comparable.class);
return deserialized;
} catch (Exception e) {
}
return null;
}
#Override
public void writeObject(#NotNull LightOutputStream output, #NotNull Comparable object) {
byte[] serialized = serialize(object);
output.write(serialized);
}
public static byte[] serialize(Object obj) {
try {
try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutput out = new ObjectOutputStream(bos)) {
out.writeObject(obj);
return bos.toByteArray();
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
public static <T> T deserialize(byte[] data, Class<T> clazz) {
try {
ByteArrayInputStream in = new ByteArrayInputStream(data);
ObjectInputStream is = new ObjectInputStream(in);
return (T) is.readObject();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return null;
}
}
I am afraid that my approach might be a bit overkill for the simple job of saving a null value?

It's safe to registerCustomPropertyType several times, though it is intended to be called usually once on an init stage.
If I really need to distinguish lack of property value and property having null value, then I'd try to define non-null values replacing null. For String, it can be hex representation of an UUID. For Integer, Integer.MIN_VALUE or Integer.MAX_VALUE, etc. Don't use values of mixed types for a single property, otherwise search by property value or range search won't work.

How to disable Caching at runtime if Couchbase connection failed?

I have a similar problem as asked here - How to disable Redis Caching at run time if redis connection failed. My application is using #Cacheable at the service layer for most of the database/static resources call.
Cache is backed by Couchbase and whenever application fails to connect Couchbase node application goes down. Which is what we are not expecting, we expect data should be served from the source system whenever connection failed.
We tried implementing CacheErrorHandler but it does not work as expected because we want to execute the actual method which is making a service call and return the response rather than logging the Cache fail, basically bypassing the cache and as soon as the Couchbase node is up or connection established get the data from cache.
Any idea how we can achieve it?

Thanks #Daniel Bickler for the suggestion, below is the implementation I written referring #John Blum answer.
CouchbaseCustomCacheManager:
import java.util.Map;
import org.springframework.cache.Cache;
import com.couchbase.client.spring.cache.CacheBuilder;
import com.couchbase.client.spring.cache.CouchbaseCacheManager;
public class CouchbaseCustomCacheManager extends CouchbaseCacheManager {
public CouchbaseCustomCacheManager(
final Map<String, CacheBuilder> initialCaches) {
super(initialCaches);
}
#Override
public Cache getCache(String name) {
return new CouchbaseCacheWrapper(super.getCache(name));
}
protected static class CouchbaseCacheWrapper implements Cache {
private final Cache delegate;
public CouchbaseCacheWrapper(Cache couchbaseCache) {
this.delegate = couchbaseCache;
}
#Override
public String getName() {
try {
return delegate.getName();
} catch (Exception e) {
return null;
}
}
#Override
public Object getNativeCache() {
try {
return delegate.getNativeCache();
} catch (Exception e) {
return null;
}
}
#Override
public ValueWrapper get(Object key) {
try {
return delegate.get(key);
} catch (Exception e) {
return null;
}
}
#Override
public <T> T get(Object key, Class<T> type) {
try {
return delegate.get(key, type);
} catch (Exception e) {
return null;
}
}
#Override
public void put(Object key, Object value) {
try {
delegate.put(key, value);
} catch (Exception e) {
try {
handleErrors(e);
} catch (Exception e1) {
}
}
}
#Override
public ValueWrapper putIfAbsent(Object key, Object value) {
try {
return delegate.putIfAbsent(key, value);
} catch (Exception e) {
return null;
}
}
#Override
public void evict(Object key) {
try {
delegate.evict(key);
} catch (Exception e) {
try {
handleErrors(e);
} catch (Exception e1) {
}
}
}
#Override
public void clear() {
try {
delegate.clear();
} catch (Exception e) {
try {
handleErrors(e);
} catch (Exception e1) {
}
}
}
protected <T> T handleErrors(Exception e) throws Exception {
if (e instanceof Exception) {
return null;
} else {
throw e;
}
}
}
}
And used it as:
#Bean
public CacheManager cacheManager() {
final Map<String, CacheBuilder> cache = new HashMap<>();
for (final String appCache : "127.0.0.1,127.0.0.2,127.0.0.3".split(",")) {
cache.put(appCache, CacheBuilder.newInstance(CouchbaseCluster.create().openBucket(
"default", "")));
}
return new CouchbaseCustomCacheManager(cache);
}

XStream registers only one converter

On my serialized XML File is only one attribute of my Object saved, although four should be saved. I think this is due to y XStream Object registering only one converter, although he should register four.
My Converters are all functioning individually. I tested them one by one.
My XML File:
<object-stream>
<model.Product>13</model.Product>
</object-stream>
My Product class which should be saved:
public class Product implements Externalizable, Serializable {
private static final long serialVersionUID = -8437751114305532162L;
#XStreamConverter(converter.NameConverter.class)
private SimpleStringProperty name;
#XStreamConverter(converter.PriceConverter.class)
private SimpleDoubleProperty price;
#XStreamConverter(converter.CountConverter.class)
private SimpleIntegerProperty quantity;
#XStreamConverter(converter.IDConverter.class)
private long id;
public Product(String name, int quantity, double price, long id)
{
this.name=new SimpleStringProperty(name);
this.quantity=new SimpleIntegerProperty(quantity);
this.price=new SimpleDoubleProperty(price);
this.id=id;
//Getter and Setter and implentation of Externalizable
My XStream class
XStream xstream;
ObjectInputStream ois;
ObjectOutputStream oos;
#Override
public void close() throws IOException {
if (oos != null) {
oos.close();
}
if (ois != null) {
ois.close();
}
}
#Override
public void writeObject(Product obj) throws IOException {
try {
oos.writeObject(obj);
} catch (Exception e) {
e.printStackTrace();
}
}
public void open(InputStream input, OutputStream output) throws IOException {
xstream = createXStream(model.Product.class);
converter.ConverterManager con=new ConverterManager();
con.registerAllConverters(xstream);
if (input != null) {
if (input.available() > 0) {
ois = xstream.createObjectInputStream(input);
}
}
if (output != null) {
oos = xstream.createObjectOutputStream(output);
}
}
}
My ConverterManager:
import com.thoughtworks.xstream.XStream;
public class ConverterManager {
public void registerAllConverters(XStream xstream)
{
xstream.aliasAttribute("Product Price", "price");
xstream.registerConverter(new PriceConverter());
xstream.aliasAttribute("Product ID", "id");
xstream.registerConverter(new IDConverter());
xstream.aliasAttribute("Product Name", "name");
xstream.registerConverter(new NameConverter());
xstream.aliasAttribute("Product quantity", "quantity");
xstream.registerConverter(new CountConverter());
}
}
My writeObject, open and close methods are called from this method from another class:
private void saveModel() {
XStreamStrategy s=new XStreamStrategy();
try {
s.open(getFilePath());
} catch (IOException e) {
e.printStackTrace();
}
for(fpt.com.Product p: model)
{
try {
s.writeObject(p);
} catch (IOException e) {
e.printStackTrace();
}
}
try {
s.close();
} catch (IOException e) {
e.printStackTrace();
}
}

How to test the "key" and "value" of config.properties file?

I have a class ReadPropertyFile which has a method getPropertyFor() of return type string(which is the value corresponding to key passed as parameter).I need help to test the getPropertyFor() method for both value and the key using Junit.
public class ReadPropertyFile {
private Properties properties;
public ReadPropertyFile(String propertyFileName) {
properties= new Properties();
try {
properties.load(new FileReader(propertyFileName));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public String getPropertyFor(String key) {
String value = properties.getProperty(key);
if(value == null) {
try {
throw new Exception(key + " not found!");
} catch (Exception e) {
e.printStackTrace();
}
}
return value;
}
}
I have written the following test case to test the value for the key provided.
How do I test the "key" whether it is contained in the testconfig.properties file?
The contents of the testConfig.properties are as follows:
FILE_NAME=D:/Refreshed_data_daily/all_hue_posts_in_excel.xlsx

If the key is not defined in the file,
the getProperties method returns null.
If the key exists but has no value,
the getProperties method returns an empty string.
The way you catch and throw exception in the file doesn't make much sense.
You could simplify your method as:
public String getPropertyFor(String key) {
return properties.getProperty(key);
}
Given this content in testConfig.properties:
FILE_NAME = D:/Refreshed_data_daily/all_hue_posts_in_excel.xlsx
empty.test =
You could unit test the different cases like this:
private String getProperty(String key) {
new ReadPropertyFile("testConfig.properties").getPropertyFor(key)
}
#Test
public void testMissingKey() {
assertNull(getProperty("nonexistent"));
}
#Test
public void testEmptyKey() {
assertEquals("", getProperty("empty.prop"));
}
#Test
public void testValue() {
assertEquals("D:/Refreshed_data_daily/all_hue_posts_in_excel.xlsx", getProperty("FILE_NAME"));
}

Is needed Return value or not?, Working with try, catch and Finally: Java

I have this code:
private String Style(String Arg, Vector VctrClass) throws Exception {
if (Verify that Arg is contained into VctrClass)) {
return "Something";
} else {
throw new Exception("Error The argument required \""+Arg+"\" doesn't exist<br>");
}
}
Here my problem, I had this method:
public String GetStylString(String Arg) {
try {
return this.Style(Arg,OneVector);
}
catch(Exception e) {
System.out.println(e.toString());
}
finally {
return "";
}
}
But' I have this message:
Void methods cannot return a value
Then I changed my method to:
public String GetStylString(String Arg) {
try {
return this.Style(Arg,OneVector);
}
catch(Exception e) {
System.out.println(e.toString());
}
}
I have this message:
This method must return a result of type String

Add the return after the println, not in the finally:
public String GetStylString(String Arg) {
try {
return this.Style(Arg,OneVector);
}
catch(Exception e) {
System.out.println(e.toString());
return "";
}
}

Add the return after the catch instead of in the finally:
public String GetStylString(String Arg) {
try {
return this.Style(Arg,OneVector);
}
catch(Exception e) {
System.out.println(e.toString());
}
return "";
}