I'm a Java (Android) beginner (coming from Python) and I'm trying to catch an exception using Try-Catch as follows:
try {
u.save();
} catch (Exception e) {
Log.wtf("DO THIS", " WHEN SAVE() FAILS");
}
To my surprise I don't see my Log message but I still get the following error:
09-25 10:53:32.147: E/SQLiteDatabase(7991):
android.database.sqlite.SQLiteConstraintException: error code 19:
constraint failed
Why doesn't it catch the Exception? Am I doing something wrong here? All tips are welcome!
The save() method looks as follows:
public final void save() {
final SQLiteDatabase db = Cache.openDatabase();
final ContentValues values = new ContentValues();
for (Field field : mTableInfo.getFields()) {
final String fieldName = mTableInfo.getColumnName(field);
Class<?> fieldType = field.getType();
field.setAccessible(true);
try {
Object value = field.get(this);
if (value != null) {
final TypeSerializer typeSerializer = Cache.getParserForType(fieldType);
if (typeSerializer != null) {
// serialize data
value = typeSerializer.serialize(value);
// set new object type
if (value != null) {
fieldType = value.getClass();
// check that the serializer returned what it promised
if (!fieldType.equals(typeSerializer.getSerializedType())) {
Log.w(String.format("TypeSerializer returned wrong type: expected a %s but got a %s",
typeSerializer.getSerializedType(), fieldType));
}
}
}
}
// TODO: Find a smarter way to do this? This if block is necessary because we
// can't know the type until runtime.
if (value == null) {
values.putNull(fieldName);
}
else if (fieldType.equals(Byte.class) || fieldType.equals(byte.class)) {
values.put(fieldName, (Byte) value);
}
else if (fieldType.equals(Short.class) || fieldType.equals(short.class)) {
values.put(fieldName, (Short) value);
}
else if (fieldType.equals(Integer.class) || fieldType.equals(int.class)) {
values.put(fieldName, (Integer) value);
}
else if (fieldType.equals(Long.class) || fieldType.equals(long.class)) {
values.put(fieldName, (Long) value);
}
else if (fieldType.equals(Float.class) || fieldType.equals(float.class)) {
values.put(fieldName, (Float) value);
}
else if (fieldType.equals(Double.class) || fieldType.equals(double.class)) {
values.put(fieldName, (Double) value);
}
else if (fieldType.equals(Boolean.class) || fieldType.equals(boolean.class)) {
values.put(fieldName, (Boolean) value);
}
else if (fieldType.equals(Character.class) || fieldType.equals(char.class)) {
values.put(fieldName, value.toString());
}
else if (fieldType.equals(String.class)) {
values.put(fieldName, value.toString());
}
else if (fieldType.equals(Byte[].class) || fieldType.equals(byte[].class)) {
values.put(fieldName, (byte[]) value);
}
else if (ReflectionUtils.isModel(fieldType)) {
values.put(fieldName, ((Model) value).getId());
}
else if (ReflectionUtils.isSubclassOf(fieldType, Enum.class)) {
values.put(fieldName, ((Enum<?>) value).name());
}
}
catch (IllegalArgumentException e) {
Log.e(e.getClass().getName(), e);
}
catch (IllegalAccessException e) {
Log.e(e.getClass().getName(), e);
}
}
if (mId == null) {
mId = db.insert(mTableInfo.getTableName(), null, values);
}
else {
db.update(mTableInfo.getTableName(), values, "Id=" + mId, null);
}
Cache.getContext().getContentResolver()
.notifyChange(ContentProvider.createUri(mTableInfo.getType(), mId), null);
}
There are two classes to catch the problems.
Error
Exception
Both are sub-class of Throwable class. When there is situation we do not know, that particular code block will throw Exception or Error? You can use Throwable. Throwable will catch both Errors & Exceptions.
Do this way
try {
u.save();
} catch (Throwable e) {
e.printStackTrace();
}
Constraint failed usually indicates that you did something like pass a null value into a column that you declare as not null when you create your table.
do this way
try {
// do some thing which you want in try block
} catch (JSONException e) {
e.printStackTrace();
Log.e("Catch block", Log.getStackTraceString(e));
}
Try
try {
u.save();
} catch (SQLException sqle) {
Log.wtf("DO THIS", " WHEN SAVE() FAILS");
}catch (Exception e) {
Log.wtf("DO THIS", " WHEN SAVE() FAILS");
}
Log is expecting certain variable-names like verbose(v), debug(d) or info(i).
Your "wtf" doesnt belong there. Check this answer for more info -->
https://stackoverflow.com/a/10006054/2074990
or this:
http://developer.android.com/tools/debugging/debugging-log.html
Related
You who know everything and can there is some way to reduce the lines of this code thank you. is that in my subject they ask us to reduce the codes in their maximum possible and I do not know how to do it with this
Cliente cliente=new Cliente(agregar.txt_cedulaCliente.getText(), agregar.txt_nombreCliente.getText(), agregar.txt_tfCliente.getText(), agregar.txt_direccion.getText(), null);
if (ordenIngreso.equals("primero")) {
menu.centralCliente.insertarAlComienzo(cliente);
} else {
if (menu.centralCliente.getPrimero() != null) {
if (ordenIngreso.equals("antes")) {
if (!txtCodigoAnterior.getText().equals(null)) {
try {
menu.centralCliente.insertarAntesDe(txtCodigoAnterior.getText(), cliente);
} catch (NoExisteException ex) {
Logger.getLogger(OrdenCliente.class.getName()).log(Level.SEVERE, null, ex);
}
}
} else if (ordenIngreso.equals("despues")) {
if (!txtCodigoSiguiente.getText().equals("")) {
if (menu.centralCliente.buscarCliente(txtCodigoSiguiente.getText()) != null) {
try {
menu.centralCliente.insertarDespuesDe(txtCodigoSiguiente.getText(), cliente);
} catch (NoExisteException ex) {
Logger.getLogger(OrdenCliente.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
} else if (ordenIngreso.equals("ultimo")) {
menu.centralCliente.insertarAlFinal(cliente);
}
} else {
JOptionPane.showMessageDialog(null, "No hay clientes en la lista");
}
}
when you only have if block, with no else, you should use
if (statement && statement)
instead of
if (statement) {
if (statement) {
....
so in your case, use
if (!txtCodigoSiguiente.getText().equals("") && menu.centralCliente.buscarCliente(txtCodigoSiguiente.getText()) != null) {
try {
menu.centralCliente.insertarDespuesDe(txtCodigoSiguiente.getText(), cliente);
} catch (NoExisteException ex) {
Logger.getLogger(OrdenCliente.class.getName()).log(Level.SEVERE, null, ex);
}
}
Let's imagine that we have to call one method from different classes by definition coming at run time. For example we receive JSON like this:
{"calculator": "MyClass1", "parameter1": 1.0, "parameter2": 2.0, ... }
MyClass1 and more classes either extend some base class or implement some interface (just to be able to enumerate them at run time). We have to create object, pass the parameters to the object and call calculate() method.
I can think of two ways to do this:
switch(calculatorString) { case "MyClass1": calculator = new MyClass1(); ...
using Java Reflection
The first way is really stupid because the code must be updated each time new calculator class is added to the project. The second way is slightly better, but the IDE is unable to catch any type errors we make while creating the objects and invoking the method.
Are there other ways to do this (possibly better)?
You could maybe use the Java Service Provider Interface:
See for example here:
https://docs.oracle.com/javase/tutorial/sound/SPI-intro.html
https://www.baeldung.com/java-spi
It allows for different implementations/services that you implement (you still need class names in the services files) but don't have to use reflection directly.
You define the service providers in the META-INF
META-INF/services/com.baeldung.rate.spi.ExchangeRateProvider
Your services can register themselves and if you allow them to use the input json, you will be very flexible.
Reflection is the best way to create object at runtime, but its all depend on usecase.
You can also use factory design pattern for object Creation.
Using ReflectionAPI
try {
cls = Class.forName(className);
instance = cls.newInstance();
instance = BeanUtils.populateBean(properties, cls);
} catch (Exception e) {
e.printStackTrace();
}
BeanUtil Class
public static Object populateBean(Map<String, Object> propertyMap, Class<?> clazz) throws Exception {
PropertyUtilsBean bean = new PropertyUtilsBean();
Object obj = null;
try {
obj = clazz.newInstance();
for(Map.Entry<String, Object> entrySet: propertyMap.entrySet()) {
PropertyDescriptor descriptor = null;
try {
descriptor =
bean.getPropertyDescriptor(obj, entrySet.getKey());
if (descriptor == null) {
continue;
}
Method writeMethod = bean.getWriteMethod(descriptor);
writeMethod.invoke(obj, convert(descriptor.getPropertyType(), entrySet.getValue(), DATE_PATTERN));
} catch (IncompatibleConversion e) {
throw e;
} catch (Exception e) {
throw new Exception("Unable to parse");
}
}
}catch(Exception e) {
throw e;
}
return obj;
}
Convert Class
private static Object convert(Class<?> clzz, Object value, String datePattern) throws Exception {
if (clzz.isAssignableFrom(BigInteger.class)) {
if (value == null) {
return value;
}
if (value instanceof BigInteger) {
return value;
}
try {
return new BigInteger(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(BigDecimal.class)) {
if (value == null) {
return value;
}
if (value instanceof BigDecimal) {
return parseBigDecimal(value.toString(), DECIMAL_PRECISION);
}
try {
return parseBigDecimal(value.toString(), DECIMAL_PRECISION);
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Integer.class)) {
if (value == null) {
return value;
}
if (value instanceof Integer) {
return value;
}
try {
return new Integer(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Long.class)) {
if (value == null) {
return value;
}
if (value instanceof Long) {
return value;
}
try {
return new Long(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(String.class)) {
if (value == null) {
return value;
}
if (value instanceof String) {
return value;
}
try {
return value.toString();
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Date.class)) {
if (value == null) {
return value;
}
if (value instanceof Date) {
return value;
}
if (datePattern == null) {
throw new Exception("date pattern cannot be null");
}
try {
SimpleDateFormat sdf = new SimpleDateFormat(datePattern);
return sdf.parse(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Byte.class)) {
if (value == null) {
return value;
}
if (value instanceof Byte) {
return (value);
} else if (value instanceof Number) {
return new Byte(((Number) value).byteValue());
}
try {
return (new Byte(value.toString()));
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Float.class)) {
if (value == null) {
return value;
}
if (value instanceof Float) {
return (value);
}
try {
return new Float(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
} else if (clzz.isAssignableFrom(Double.class)) {
if (value == null) {
return value;
}
if (value instanceof Double) {
return (value);
}
try {
return new Double(value.toString());
} catch (Exception e) {
throw new IncompatibleConversion(e);
}
}
throw new Exception("Incompactible Conversion");
}
Spring has made it so incredibly easy to set up application properties...but how would you do it without Spring?
I need to deploy a Java / Groovy application to a server where using Spring is out of the question... and I also don't have the liberty to install anything like Redis either. One option I am considering is to set up a Spring Cloud Config Server elsewhere and have my application consume properties from the config server. Trouble is, that is a bit of an overkill for my project now.
Could anyone suggest a way to do this in good, old, plain Java? :)
This is a really simple and basic example, but you can modify it as you like:
PropertyConfigurator.java
public class PropertiesConfigurator
{
Properties properties = new Properties();
String configInputPath = null;
InputStream configInputStream = null;
public PropertiesConfigurator(String configInputPath)
{
this.configInputPath = configInputPath;
}
public PropertiesConfigurator load() throws IOException, PropertyException
{
try
{
this.configInputStream = new FileInputStream(this.configInputPath);
// load a properties file
this.properties.load(this.configInputStream);
validate();
}
catch (IOException ex)
{
System.out.println("Failed load properties file: " + this.configInputPath);
throw ex;
}
catch (PropertyException ex)
{
System.out.println("One or more properties are empty");
throw ex;
}
finally
{
if (this.configInputStream != null)
{
try
{
this.configInputStream.close();
}
catch (IOException ex)
{
System.out.println("Failed to close input stream");
throw ex;
}
}
}
return this;
}
private void validate() throws PropertyException
{
Enumeration<?> e = this.properties.propertyNames();
while (e.hasMoreElements())
{
String key = (String) e.nextElement();
String value = this.properties.getProperty(key);
if (value.isEmpty())
{
System.out.println(String.format("Property %s is empty!", key));
throw new PropertyException("One or more properties are empty");
}
}
}
public String getProperty(String key)
{
return this.properties.getProperty(key);
}
#Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (!(o instanceof PropertiesConfigurator))
return false;
PropertiesConfigurator that = (PropertiesConfigurator) o;
if (properties != null ? !properties.equals(that.properties) : that.properties != null)
return false;
if (configInputPath != null ? !configInputPath.equals(that.configInputPath) : that.configInputPath != null)
return false;
return configInputStream != null ?
configInputStream.equals(that.configInputStream) :
that.configInputStream == null;
}
#Override
public int hashCode()
{
int result = properties != null ? properties.hashCode() : 0;
result = 31 * result + (configInputPath != null ? configInputPath.hashCode() : 0);
result = 31 * result + (configInputStream != null ? configInputStream.hashCode() : 0);
return result;
}
}
PropertyException.java
public class PropertyException extends Exception
{
public PropertyException()
{
}
public PropertyException(String message)
{
super(message);
}
public PropertyException(String message, Throwable throwable)
{
super(message, throwable);
}
}
MainRunner.java
public class MainRunner
{
public static void main(String[] args)
{
try
{
String configFilePath = "application.properties";
PropertiesConfigurator propertiesConfigurator = new PropertiesConfigurator(configFilePath).load();
String prop1 = propertiesConfigurator.getProperty("keyprop1");
// Do whatever you want with prop1
// ...
}
catch (PropertyException ex)
{
System.out.println("Failed to load properties");
System.exit(1);
}
catch (Exception ex)
{
System.out.println("Error in main application");
System.exit(1);
}
}
}
Example of application.properties
keyprop1=value1
keyprop2=value2
Again, it's very basic and you should definitely improve this code and add your logic, validation, etc.
Take a look at http://constretto.org. That's easy to use configuration framework.
I want to create an instance of a class, but I also need to initialize also all its fields recursively.
The code you see related do the objectFactory is because some of this classes could be JAXB classes, so for every package there is an ObjectFactory with methods like createJaxbObject(....).
EDITED:
My final solutions is this one:
public Object getInstance(Class<?> instanceClass, Boolean simple,
String jaxbName) {
Object instance = null;
try {
if (instanceClass.isPrimitive())
return primitiveValues.get(instanceClass.getName());
if (List.class.isAssignableFrom(instanceClass))
return new ArrayList();
else if (instanceClass.isEnum())
return instanceClass.getEnumConstants()[0];
else if (instanceClass.isArray())
return java.lang.reflect.Array.newInstance(instanceClass, 1);
else if (BigInteger.class.isAssignableFrom(instanceClass))
return new BigInteger("0");
else if (instanceClass.equals(String.class))
return "";
else if (instanceClass.equals(Boolean.class))
return false;
else if (instanceClass.equals(EntityObjectStringType.class))
return new EntityObjectStringType();
else if (JAXBElement.class.isAssignableFrom(instanceClass)) {
try {
Method m = null;
Class<?> objFactoryClass = null;
Iterator<String> it = EditorServlet.objectFactories
.iterator();
Object of = null;
while (it.hasNext()) {
objFactoryClass = Class.forName(it.next());
of = objFactoryClass.getConstructor().newInstance();
m = getMethodFromObjectFactory(objFactoryClass,
jaxbName);
if (m != null)
if (m.getParameterTypes().length > 0)
break;
}
Object jaxbElement = getInstance(m.getParameterTypes()[0],
m.getParameterTypes()[0].getSimpleName());
return m.invoke(of, jaxbElement);
} catch (NoSuchMethodException e) {
logger.error("JAXB NoSuchMethodException");
}
} else
try {
logger.info("Costruttori per " + instanceClass.getName()
+ " " + instanceClass.getConstructors().length);
instance = instanceClass.getConstructor().newInstance();
} catch (NoSuchMethodException noSuchMethodException) {
logger.error("getConstructors NoSuchMethodException");
}
} catch (IllegalArgumentException e) {
logger.error("IllegalArgumentException " + instanceClass.getName());
} catch (SecurityException e) {
logger.error("SecurityException " + instanceClass.getName());
} catch (InstantiationException e) {
logger.error("InstantiationException " + instanceClass.getName()
+ " " + instanceClass.isPrimitive());
} catch (IllegalAccessException e) {
logger.error("IllegalAccessException " + instanceClass.getName());
} catch (InvocationTargetException e) {
logger.error("InvocationTargetException " + instanceClass.getName());
} catch (ClassNotFoundException e) {
logger.error("ClassNotFoundException " + instanceClass.getName());
}
if (!simple) {
for (Field field : instanceClass.getDeclaredFields()) {
try {
Object fieldInstance = getInstance(field.getType(),
field.getName());
field.setAccessible(true);
field.set(instance, fieldInstance);
} catch (IllegalArgumentException e) {
logger.error("IllegalArgumentException "
+ instanceClass.getName());
} catch (IllegalAccessException e) {
logger.error("IllegalAccessException "
+ instanceClass.getName());
}
}
}
return instance;
}
If I could hazard a guess, you're calling your method recursively in your NoSuchMethodException catch.
Object of = getInstance(objFactoryClass);
If your recursive call keeps on not finding the method on:
Method m = getMethodFromObjectFactory(objFactoryClass, c);
... the method will call itself again, which should end with a StackOverflowError at some point.
Your recursion has no break point
Try to stop recursion where the class is primary type:
if (List.class.isAssignableFrom(c))
instance = new ArrayList();
else if (c.isEnum())
return c.getEnumConstants()[0]; //avoid stackoverflow error
else if(c.isPrimitive()) {
instance = c.getConstructor().newInstance();
// use must stop here
return instance;
} else{
instance = c.getConstructor().newInstance();
}
The isPrimitive will judge whether the class is primary type(int ,Integer,shor,Short,String...)
I am trying to set a number of Enums to default value I am using the following method:
private void checkEnum(Field field, String setMethod) {
// TODO Auto-generated method stub
try {
String className = Character.toUpperCase(field.getName().charAt(0)) +
field.getName().substring(1);
Class<?> cls = Class.forName("com.citigroup.get.zcc.intf." + className);
Object[] enumArray = cls.getEnumConstants();
//set to the last Enum which is unknown
invoke(setMethod, enumArray[enumArray.length - 1] );
} catch(Exception e) {
System.out.println(e.toString());
}
}
The problem is actually setting the Enum. I have extracted the enum type but to then call the MethodInvoker. Passing in the Enum object is proving a problem. All the enums have the following as the last element of the enum array.
EnumName.UNKNOWN
However this is not being set via the invoke method which looks like:
private Object invoke(String methodName, Object newValue) {
Object value = null;
try {
methodInvoker.setTargetMethod(methodName);
if (newValue != null) {
methodInvoker.setArguments(new Object[]{newValue});
} else {
methodInvoker.setArguments(new Object[]{});
}
methodInvoker.prepare();
value = methodInvoker.invoke();
} catch (ClassNotFoundException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(),e);
} catch (NoSuchMethodException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(),e);
} catch (java.lang.reflect.InvocationTargetException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(),e);
} catch (IllegalAccessException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(),e);
}
return value;
}
So I'm lost as to why the
invoke(setMethod, enumArray[enumArray.length -1] );
Is not setting my Enum
I attempted to get your code running. The methodInvoker.prepare() call was throwing:
java.lang.IllegalArgumentException: Either 'targetClass' or 'targetObject' is required
So I added in the class missing parameter and the code works, if I understand your use case.
You appear to be setting a static field whose name must be the name of an Enum class under com.citigroup.get.zcc.intf with the first character in the field name downcased.
Here is my modified code:
public void checkEnum(Field field, String setMethod, Class clazz) {
try {
String className = Character.toUpperCase(field.getName().charAt(0)) +
field.getName().substring(1);
Class<?> cls = Class.forName("com.citigroup.get.zcc.intf." + className);
Object[] enumArray = cls.getEnumConstants();
//set to the last Enum which is unknown
invoke(setMethod, enumArray[enumArray.length - 1], clazz);
} catch (Exception e) {
System.out.println(e.toString());
}
}
private Object invoke(String methodName, Object newValue, Class clazz) {
Object value = null;
try {
MethodInvoker methodInvoker = new MethodInvoker(); // this was missing
methodInvoker.setTargetMethod(methodName);
methodInvoker.setTargetClass(clazz); // This was missing
if (newValue != null) {
methodInvoker.setArguments(new Object[]{newValue});
} else {
methodInvoker.setArguments(new Object[]{});
}
methodInvoker.prepare();
value = methodInvoker.invoke();
} catch (ClassNotFoundException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(), e);
} catch (NoSuchMethodException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(), e);
} catch (java.lang.reflect.InvocationTargetException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(), e);
} catch (IllegalAccessException e) {
throw new IllegalStateException("Method invocation failed. " + e.getMessage(), e);
}
return value;
}
}
My test code resembled (Show is an enum class of mine, MethodNameHelper has been previously posted to StackExchange):
public class StackExchangeTestCase {
protected static final Logger log = Logger.getLogger(StackExchangeTestCase.class);
public static Show show;
public static void setShow(Show newShow) {
show = newShow;
}
#Test
public void testJunk() throws Exception {
Method me = (new Util.MethodNameHelper(){}).getMethod();
Class<?> aClass = me.getDeclaringClass();
Field att1 = aClass.getField("show");
show = null;
methodNameHelper.checkEnum(att1, "setShow", aClass);
System.out.println(show); // worked
}
}