Develop Reference

Guice, Type Conversion When Getting Values from Properties

The following Guice module binds a property file to the #Named annotation.
import com.google.inject.AbstractModule;
import com.google.inject.name.Names;
// Omitted: other imports
public class ExampleModule extends AbstractModule {
#Override
protected void configure() {
Names.bindProperties(binder(), getProperties());
}
private Properties getProperties() {
// Omitted: return the application.properties file
}
}
I can now inject properties directly into my classes.
public class Example {
#Inject
#Named("com.example.title")
private String title;
#Inject
#Named("com.example.panel-height")
private int panelHeight;
}
The values read from a properties file are strings but, as you can see in the example above, Guice is capable of doing type conversion for int fields.
Now, given the property com.example.background-color=0x333333 I would like to able to get the same type conversion for an arbitrary class, like:
public class Example {
#Inject
#Named("com.example.background-color")
private Color color;
}
Let's say that the Color class contains a static method decode() and I can obtain a new Color instance by calling Color.decode("0x333333").
How can I configure Guice to do this automatically and behind the scenes for me?

I found a solution by myself looking into the Guice sources, although I have to say it's not the prettiest (more on this later on).
First of all, we need to create a TypeConverter.
import com.google.inject.TypeLiteral;
import com.google.inject.spi.TypeConverter;
// Omitted: other imports
public class ColorTypeConverter implements TypeConverter {
#Override
public Object convert(String value, TypeLiteral<?> toType) {
if (!toType.getRawType().isAssignableFrom(Color.class)) {
throw new IllegalArgumentException("Cannot convert type " + toType.getType().getTypeName());
}
if (value == null || value.isBlank()) {
return null;
}
return Color.decode(value);
}
}
Then, a Matcher. I generalized.
import com.google.inject.TypeLiteral;
import com.google.inject.matcher.AbstractMatcher;
// Omitted: other imports
public class SubclassMatcher extends AbstractMatcher<TypeLiteral<?>> {
private final Class<?> type;
public SubclassMatcher(Class<?> type) {
this.type = type;
}
#Override
public boolean matches(TypeLiteral<?> toType) {
return toType.getRawType().isAssignableFrom(type);
}
}
Finally, add the following line to the Guice module.
import com.google.inject.AbstractModule;
// Omitted: other imports
public class ExampleModule extends AbstractModule {
#Override
protected void configure() {
binder().convertToTypes(new SubclassMatcher(Color.class), new ColorTypeConverter());
// Omitted: other configurations
}
}
Now, the following injection works.
public class Example {
#Inject
#Named("com.example.background-color")
private Color backgroundColor;
}
It could be prettier. There exists a com.google.inject.matcher.Matchers API which I wasn't able use and could have solved my problem without constructing my personal SubclassMatcher class. See, Matchers.subclassesOf(Class<?>). It's for sure my fault as I don't believe Google wouldn't think of this pretty common use-case. If you find a way to make it work, please leave a comment.

Guice can't do that for you.
I suppose the conversion from String to int happens upon injection and not when you call Names.bindProperties(...)
See the bindProperties methods:
/** Creates a constant binding to {#code #Named(key)} for each entry in {#code properties}. */
public static void bindProperties(Binder binder, Map<String, String> properties) {
binder = binder.skipSources(Names.class);
for (Map.Entry<String, String> entry : properties.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
binder.bind(Key.get(String.class, new NamedImpl(key))).toInstance(value);
}
}
/**
* Creates a constant binding to {#code #Named(key)} for each property. This method binds all
* properties including those inherited from {#link Properties#defaults defaults}.
*/
public static void bindProperties(Binder binder, Properties properties) {
binder = binder.skipSources(Names.class);
// use enumeration to include the default properties
for (Enumeration<?> e = properties.propertyNames(); e.hasMoreElements(); ) {
String propertyName = (String) e.nextElement();
String value = properties.getProperty(propertyName);
binder.bind(Key.get(String.class, new NamedImpl(propertyName))).toInstance(value);
}
}
They are just binding strings.
You could just copy one of them and create your own binding. If the property value is in a color format, bind it additionally as Color.
As an example:
public class GuiceColors {
public static class GameModule extends AbstractModule {
#Override
protected void configure() {
Properties props = new Properties();
try {
props.load(getClass().getResourceAsStream("application.properties"));
} catch (IOException e) {
e.printStackTrace();
}
bindPropertiesWithColors(props);
}
private void bindPropertiesWithColors(Properties properties) {
Binder binder2 = binder().skipSources(Names.class);
// use enumeration to include the default properties
for (Enumeration<?> e = properties.propertyNames(); e.hasMoreElements();) {
String propertyName = (String) e.nextElement();
String value = properties.getProperty(propertyName);
try {
Color decodedColor = Color.decode(value);
binder2.bind(Key.get(Color.class, Names.named(propertyName)))
.toInstance(decodedColor);
} catch (NumberFormatException ex) {
// property value cannot be decoded as color, ignore the exception
}
binder2.bind(Key.get(String.class, Names.named(propertyName))).toInstance(value);
}
}
}
public static class Example {
#Inject
#Named("com.example.background-color")
private Color color;
#Inject
#Named("com.example.background-color")
private String colorString;
}
public static void main(String[] args) {
Injector injector = Guice.createInjector(new GameModule());
System.out.println(injector.getInstance(Example.class).color);
System.out.println(injector.getInstance(Example.class).colorString);
}
}
with application.properties being:
com.example.background-color = 0x333333

How to get configuration value for static value in Quarkus

I am rewriting exceptions from an old system and everything was working, but I needed make BAD_REQUEST configurable.
private static final String BAD_REQUEST = "BDRQ";
I tried to just put ConfigProperty, but it doesn't work.
import javax.ws.rs.core.Response.Status;
import org.eclipse.microprofile.config.inject.ConfigProperty;
public class SXClientException extends RuntimeException {
#ConfigProperty(name = "greeting.error", defaultValue = "BDRQ")
public String BAD_REQUEST;
private final RuntimeException runtimeException;
public SXClientException(RuntimeException e) {
super(e);
this.runtimeException = e;
}
public Status getStatus() {
if (BAD_REQUEST.equals(runtimeException.getMessage())) {
return Status.BAD_REQUEST;
}
return Status.INTERNAL_SERVER_ERROR;
}
// ...
}
It probably doesn't work since I make them without any CDI.
catch (LegacyOMException e) {
throw new SXClientException(e);
}
I would prefer to avoid creating another bean (and passing the value) just to compare one String. Any idea how can I read a configuration value for a static-ish value?

you can use org.eclipse.microprofile.config.ConfigProvider.
Works for both static and non static members.
public static final String BAD_REQUEST = ConfigProvider.getConfig().getValue("greeting.error",String.class);
public final String BAD_REQUEST = ConfigProvider.getConfig().getValue("greeting.error",String.class);

use follow method:
Properties properties = new Properties();
InputStream inputStream = this.getClass().getResourceAsStream("/menu.properties");
properties.load(inputStream );
System.out.println(properties.getProperty("a"));

How to save static variable when I serialize

My Goal: I need to keep the App state exactly in same sate after shutdown, lets say it's equivalent to "suspend" state.
My Problem : I do know that serialization mechanism doesn't save transient variables neither static variables. However I need to maintain the static variables in exactly same state after App suspension/shut down.
Approach-1 : I could save the state of static variable(s) into a different file, using my "file format", and serialize the objects into a different one.
a) Is this the "normal" approach?
Approach-2 : If I extend the ObjectInputStream/ObjectOutputStreamand override the methods readStreamHeader/writeStreamHeaderI can write whatever I want. So I can also write my static variables.
b) Am I doing something I should not?
Here's the code I've written testing approach-2, and seams to work fine. Please note, I'm not a Java programmer, so for it's very important to understand best practices, if there's any in this particular case.
#SuppressWarnings("serial")
class SequenceIdentifier implements Serializable
{
protected static long seqIdentifier_ = 1L; //This variable MUST NOT be reseted.
private long id_; //Object variable to be serialised.
private SequenceIdentifier(long id)
{ id_ = id;
}
#Override
public String toString()
{ return ("Id : " + id_ + " of " + seqIdentifier_);
}
public static SequenceIdentifier newInstance()
{ return new SequenceIdentifier(seqIdentifier_++);
}
}
final class OOStream extends ObjectOutputStream
{
public OOStream(OutputStream out) throws IOException
{ super(out);
}
#Override
protected void writeStreamHeader() throws IOException
{ super.writeLong(SequenceIdentifier.seqIdentifier_);
}
}
final class OIStream extends ObjectInputStream
{
public OIStream(InputStream in) throws IOException
{ super(in);
}
#Override
protected void readStreamHeader() throws IOException
{ SequenceIdentifier.seqIdentifier_ = super.readLong();
}
}
public class Main
{
public static void dump(ArrayList<SequenceIdentifier> ids)
{
for (SequenceIdentifier id : ids)
System.out.println(id);
}
public static void saveData()
{
ArrayList<SequenceIdentifier> ids = new ArrayList<>(Arrays.asList(SequenceIdentifier.newInstance(),
SequenceIdentifier.newInstance(),
SequenceIdentifier.newInstance(),
SequenceIdentifier.newInstance()));
try (OOStream oOut = new OOStream(new FileOutputStream("foo.bin")))
{ oOut.writeObject(ids);
} catch (Exception e)
{ System.err.println(e);
}
dump(ids);
}
#SuppressWarnings("unchecked")
public static void loadData()
{
ArrayList<SequenceIdentifier> ids = null;
try (OIStream oIn = new OIStream(new FileInputStream("foo.bin")))
{ ids = (ArrayList<SequenceIdentifier>)oIn.readObject();
} catch (Exception e)
{ System.err.println(e);
}
dump(ids);
}
public static void main(String[] args)
{
saveData();
System.out.println("Counter at this point " + SequenceIdentifier.seqIdentifier_);
SequenceIdentifier.seqIdentifier_ = 0;
loadData();
System.out.println("Counter at this point " + SequenceIdentifier.seqIdentifier_);
}
}

I would create a separate Memento-class containing all the relevant data as fields and de-/serialize that.
class MyClassWithStaticFields1 {
private static String field;
}
class MyClassWithStaticFields2 {
private static String field;
}
class StaticMemento {
String field1;
String field2;
}
// serialization
StaticMemento mem = new StaticMemento();
mem.field1 = MyClassWithStaticFields1.field;
mem.field2 = MyClassWithStaticFields2.field;
outputStream.writeObject(mem);
// deserialize
StaticMemento mem = outputStream.readObject();
MyClassWithStaticFields1.setField(mem.field1);
MyClassWithStaticFields2.setField(mem.field2);
So basically your Approach-1.

Several possibilities.
Make it non-static.
Write complementary readObect()/writeObject() methods that call defaultReadObject() and defaultWriteObject() respectively and then serialize/deserialize the field.
Write complementary writeReplace()/readResolve() methods that substitute a proxy object that does contain this member as a non-transient non-static member.
Make the object Externalizable and take complete control of the serialization process yourself in the associated methods.
Review your requirement.

Creating a HashMap of type <String , Object>

In a previous post Creating a ToolTip Managed bean
I was able to create a manged bean to collect and display tooltip text with only a single lookup and store them in an Application Scope variable. This has worked great.
I am on the rather steep part of the JAVA learning curve so please forgive me.
I have another managed bean requirement to create a HashMap Application Scope but this time it needs to be of a type String, Object. The application is where I have a single 'master' database that contains most of the code, custom controls, and XPages. This Master Database will point to One or More application databases that will store the Notes Documents specific to the application in question. So I have created in the Master a series of Application Documents that specify the RepIDs of the Application, Help and Rules databases specific to the Application along with a number of other pieces of information about the Application. This should allow me to reuse the same custom control that will open the specific DB by passing it the Application Name. As an example the Master Design DB might point to "Purchasing", "Customer Complaints", "Travel Requests" etc.
The code below works to load and store the HashMap, but I am having trouble retrieving the the data.
The compiler shows two errors one at the public Object get(String key) method and the other at mapValue = this.internalMap.get(key); in the getAppRepID method I think that it is mainly syntax but not sure. I have commented the error in the code where it appears.
/**
*This Class makes the variables that define an application within Workflo!Approval
*available as an ApplicationScope variable.
*/
package ca.wfsystems.wfsAppUtils;
import lotus.domino.Base;
import lotus.domino.Session;
import lotus.domino.Database;
import lotus.domino.View;
import lotus.domino.NotesException;
import lotus.domino.ViewColumn;
import lotus.domino.ViewEntry;
import lotus.domino.ViewEntryCollection;
import lotus.domino.Name;
import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Vector;
import com.ibm.xsp.extlib.util.ExtLibUtil;
/**
* #author Bill Fox Workflo Systems WFSystems.ca
* July 2014
* This class is provided as part of the Workflo!Approval Product
* and can be reused within this application.
* If copied to a different application please retain this attribution.
*
*/
public abstract class ApplicationUtils implements Serializable, Map<String, Object> {
private static final long serialVersionUID = 1L;
private Session s;
private Name serverName;
private String repID;
private String thisKey;
private ViewEntryCollection formVECol;
private Vector formNames;
private Database thisDB;
private Database appDB;
private View appView;
private View formView;
private ViewEntry formVE;
private ViewEntry tFormVE;
private ViewEntry ve;
private ViewEntry tVE;
private ViewEntryCollection veCol;
private final Map<String, Object> internalMap = new HashMap<String, Object>();
public ApplicationUtils() {
this.populateMap(internalMap);
}
private void populateMap(Map<String, Object> theMap) {
try{
s = ExtLibUtil.getCurrentSession();
//serverName = s.createName(s.getServerName());
thisDB = s.getCurrentDatabase();
appView = thisDB.getView("vwWFSApplications");
veCol = appView.getAllEntries();
ve = veCol.getFirstEntry();
ViewEntry tVE = null;
while (ve != null) {
rtnValue mapValue = new rtnValue();
tVE = veCol.getNextEntry(ve);
Vector colVal = ve.getColumnValues();
thisKey = colVal.get(0).toString();
mapValue.setRepID(colVal.get(2).toString());
// ...... load the rest of the values .......
theMap.put(thisKey, mapValue);
recycleObjects(ve);
ve = tVE;
}
}catch(NotesException e){
System.out.println(e.toString());
}finally{
recycleObjects(ve, veCol, appView, tVE);
}
}
public class rtnValue{
private String RepID;
private String HelpRepID;
private String RuleRepID;
private Vector FormNames;
public String getRepID() {
return RepID;
}
public void setRepID(String repID) {
RepID = repID;
}
public String getHelpRepID() {
return HelpRepID;
}
public void setHelpRepID(String helpRepID) {
HelpRepID = helpRepID;
}
public String getRuleRepID() {
return RuleRepID;
}
public void setRuleRepID(String ruleRepID) {
RuleRepID = ruleRepID;
}
public Vector getFormNames() {
return FormNames;
}
public void setFormNames(Vector formNames) {
FormNames = formNames;
}
}
public void clear() {
this.internalMap.clear();
this.populateMap(this.internalMap);
}
public boolean containsKey(Object key) {
return this.internalMap.containsKey(key);
}
public boolean containsValue(Object value) {
return this.internalMap.containsValue(value);
}
public Set<java.util.Map.Entry<String, Object>> entrySet() {
return this.internalMap.entrySet();
}
public Object get(String key) {
//error on Object get Method must return a result of type Object
try {
if (this.internalMap.containsKey(key)) {
return this.internalMap.get(key);
}
} catch (Exception e) {
System.out.println(e.toString());
rtnValue newMap = new rtnValue();
return newMap;
}
}
public boolean isEmpty() {
return this.internalMap.isEmpty();
}
public Set<String> keySet() {
return this.internalMap.keySet();
}
public Object put(String key, Object value) {
return this.internalMap.put(key, value);
}
public Object remove(Object key) {
return this.internalMap.remove(key);
}
public int size() {
return this.internalMap.size();
}
public Collection<Object> values() {
return this.internalMap.values();
}
public void putAll(Map<? extends String, ? extends Object> m) {
this.internalMap.putAll(m);
}
public String getAppRepID(String key){
/*get the Replica Id of the application database
* not sure this is the correct way to call this
*/
rtnValue mapValue = new rtnValue();
mapValue = this.internalMap.get(key);
//error on line above Type Mismatch: can not convert Object to ApplicationUtils.rtnValue
String repID = mapValue.getRepID();
}
public static void recycleObjects(Object... args) {
for (Object o : args) {
if (o != null) {
if (o instanceof Base) {
try {
((Base) o).recycle();
} catch (Throwable t) {
// who cares?
}
}
}
}
}
}

For the get() method, the way I handle that kind of situation is create a variable of the correct data type as null, in my try/catch set the variable, and at the end return the variable. So:
Object retVal = null;
try....
return retVal;
For the other error, if you right-click on the error marker, it might give you the opportunity to cast the variable to rtnValue, so:
mapValue = (rtnValue) this.internalMap.get(key)
If you haven't got it, Head First Java was a useful book for getting my head around some Java concepts. It's also worth downloading the FindBugs plugin for Domino Designer from OpenNTF. It will identify errors as well as bad practices. Just ignore the errors in the "local" package!

The problem is that there is an execution path that do not return nothing
public Object get(String key) {
//error on Object get Method must return a result of type Object
try {
if (this.internalMap.containsKey(key)) { // false
return this.internalMap.get(key);
}
} catch (Exception e) {
System.out.println(e.toString());
rtnValue newMap = new rtnValue();
return newMap;
}
}
if key is not present in the internalMap, nothing is thrown, then that method do not return anything.
To fix the problem, return the newMap at the end.
public Object get(String key) {
//error on Object get Method must return a result of type Object
try {
if (this.internalMap.containsKey(key)) {
return this.internalMap.get(key);
}
} catch (Exception e) {
System.out.println(e.toString());
}
rtnValue newMap = new rtnValue();
return newMap;
}
You can inline the return to save the allocation (which is what the compiler will do anyway). I didn't do it just to make it clear in the example.
But still you have a compiler error in getAppRepID method. You are expecting a rtnValue but you send back an Object. You must cast there.
The appropriate way to handle this is, if you know that all values are of a given type, create the map with the proper type.

Have you tried making your internalMap a map of rtnValue instances (so )?

Getting Java beans that were set in a try method

I am setting a java bean from within a try method. A text file is being read and the text that is read is used to set the java bean.
public class mainDisplay extends JPanel{
private imageDisplay id;
public mainDisplay()
{
String path;
while (1==1) {
try {
FileInputStream roadMap = new FileInputStream("C:\\Users\\Public\\Desktop\\write.txt"); //path to the text file generated
DataInputStream route = new DataInputStream(roadMap); //importing the data from the text file
BufferedReader readMe = new BufferedReader(new InputStreamReader(route));
pathOfspeed = readMe.readLine();
// id = new imageDisplay(path);
Constants.getInstance().getBean().setPath(path);
try {
Thread.sleep(40);
} catch (InterruptedException e) {
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
}
} catch (Exception e) {
System.err.println("error:" + e.getMessage());
}
System.out.println(Constants.getInstance().getBean().getPath());
}
}
That is the code from the text file reader and the code that sets the Bean.
Here is the code from the bean class:
public class Paths implements java.io.Serializable{
public String url;
public Paths(){}
public void setPath(String name){this.url=name;}
public String getPath(){return url;}
}
I then have my constants class
public class Constants {
private static Constants instance;
private Paths bean;
private Constants() {
bean=new Paths();
}
public static synchronized Constants getInstance() {
if (instance == null) {
instance = new Constants();
}
return instance;
}
public Paths getBean(){
return bean;
}
public Paths setBean(Paths p){
bean = p;
return p;
}
}
My problem then occurs when I try to get that Bean from another class:
String imageUrl=Constants.getInstance().getBean().getPath();
public test () {
System.out.println(imageUrl);
}
I get null every single time. The file reader needs to be constant as the line in the text file is changing about every minute and I need that passed to another class that uses it.
Could someone give me some suggestions as to what to do next?
Thanks

The problem is in your Constants class.
Every time you do:
Constants.Bean
it returns a newly created Path class which of course contains a null url variable which is returned to your getPath method.
You should use a Singleton for your Constants class.
Modify your Constants class:
public class Constants {
private static Constants instance;
private Paths bean;
private Constants() {
bean=new Paths();
}
public static synchronized Constants getInstance() {
if (instance == null) {
instance = new Constants();
}
return instance;
}
public Paths getBean(){
return bean;
}
public Paths setBean(Paths p){
bean = p;
}
}
Write to the Paths variable using:
Constants.getInstance().getBean().setPath("your path");
read the Paths variable;
Constants.getInstance().getBean().getPath();