We Keep Coding

How to load data from a file in a parameter and return it as a List in Java?

I'm trying to load data from "feedsfile" in the parameter and return it as a List. So far I tried it with a Scanner by adding "feedsfile" to the List "loadFeed" with the .add method, but it doesn't seem to work.
It says:"The method add(Feed) in the type List is not applicable for the arguments (File)".
#Override
public List<Feed> loadSubscribedFeeds(File feedsFile) {
List<Feed> loadFeed = new ArrayList<>();
try (Scanner s = new Scanner(new FileReader(feedsFile))) {
while (s.hasNext()) {
loadFeed.add(feedsFile);
}
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
return loadFeed;
}
Here's the Feed Class
package de.uk.java.feader.data;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import com.rometools.rome.feed.synd.SyndEntry;
import com.rometools.rome.feed.synd.SyndFeed;
import de.uk.java.feader.utils.FeaderUtils;
public class Feed implements Serializable, Comparable<Feed> {
private static final long serialVersionUID = 1L;
private String url;
private String title;
private String description;
private String publishedDateString;
private List<Entry> entries;
public Feed(String url) {
super();
this.url = url;
this.entries = new ArrayList<Entry>();
this.title = "";
this.description = "";
this.publishedDateString = "";
}
/**
* Creates an instance of a Feed and transfers the feed
* data form a SyndFeed object to the new instance.
* #param url The URL string of this feed
* #param sourceFeed The SyndFeed object holding the data for this feed instance
*/
public Feed(String url, SyndFeed sourceFeed) {
this(url);
setTitle(sourceFeed.getTitle());
setDescription(sourceFeed.getDescription());
if (sourceFeed.getPublishedDate() != null)
setPublishedDateString(FeaderUtils.DATE_FORMAT.format(sourceFeed.getPublishedDate()));
for (SyndEntry entryTemp : sourceFeed.getEntries()) {
Entry entry = new Entry(entryTemp.getTitle());
entry.setContent(entryTemp.getDescription().getValue());
entry.setLinkUrl(entryTemp.getLink());
entry.setParentFeedTitle(getTitle());
if (entryTemp.getPublishedDate() != null) {
entry.setPublishedDateString(FeaderUtils.DATE_FORMAT.format(entryTemp.getPublishedDate()));
}
addEntry(entry);
}
}
public String getUrl() {
return url;
}
public void setTitle(String title) {
this.title = title != null ? title : "";
}
public String getTitle() {
return title;
}
public void setDescription(String description) {
this.description = description != null ? description : "";
}
public String getDescription() {
return description;
}
public void setPublishedDateString(String publishedDateString) {
this.publishedDateString = publishedDateString != null ? publishedDateString : "";
}
public String getPublishedDateString() {
return publishedDateString;
}
/**
* Returns a short string containing a combination of meta data for this feed
* #return info string
*/
public String getShortFeedInfo() {
return getTitle() + " [" +
getEntriesCount() + " entries]: " +
getDescription() +
(getPublishedDateString() != null && getPublishedDateString().length() > 0
? " (updated " + getPublishedDateString() + ")"
: "");
}
public void addEntry(Entry entry) {
if (entry != null) entries.add(entry);
}
public List<Entry> getEntries() {
return entries;
}
public int getEntriesCount() {
return entries.size();
}
#Override
public boolean equals(Object obj) {
return (obj instanceof Feed)
&& ((Feed)obj).getUrl().equals(url);
}
#Override
public int hashCode() {
return url.hashCode();
}
#Override
public String toString() {
return getTitle();
}
#Override
public int compareTo(Feed o) {
return getPublishedDateString().compareTo(o.getPublishedDateString());
}
}

Problem is in line loadFeed.add(feedsFile)... You are not using scanner to read.
Try this
While(s.hasNextLine()){
loadFeed.add(s.nextLine());
}

Why are you trying to load from a file feed objects if the object returned by reading a file is String? The list should contain string instead of feed objects.
You probably need to convert contents of your file into real object take a look to how to convert a String to Object in JAVA
Try this or something similar:
import java.nio.charset.StandardCharsets;
import java.nio.file.Paths;
import java.nio.file.Files;
import java.util.stream.Collectors;
#Override
public List < Feed > loadSubscribedFeeds(File feedsFile) {
List < String > list = Files.lines(Paths.get(feedsFile.getAbsolutePath()), StandardCharsets.ISO_8859_1).collect(Collectors.toList());
List < Object > objs = new ArrayList < >();
try {
for (String s: list)
objs.add(Class.forName(s).newInstance());
//IMPORTANT! s should contain not only feed for example but com.mypackage.feed
} catch(Exception ex) {
System.out.println(ex.getMessage());
}
List < Feed > listFeed = new ArrayList < >();
for (Object l: objs) {
if (l instanceof Feed)
listFeed.add((Feed) l);
}
return listFeed;
}
If you only need the string representation of the contents of the file instead of real objects, consider changing the return type to List<String> and return list and you're already done. And if you want to keep using your code to read the strings from a file (instead of using lambdas as I did) use nextLine (and hasNextLine()) like someone as already suggested and change List<Feed> to List<String>.
The complete code using what you already wrote is the following:
public List<Feed> loadSubscribedFeeds(File feedsFile) throws IOException {
List<String> list = new ArrayList<>();
try (Scanner s = new Scanner(new FileReader(feedsFile))) {
while (s.hasNextLine()) {
list.add(s.nextLine());
}
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
List<Object> objs = new ArrayList<>();
try {
for (String s : list)
objs.add(Class.forName(s).newInstance());
//IMPORTANT! s should contain not only feed for example but com.mypackage.feed
}catch(Exception ex){
System.out.println(ex.getMessage());
}
List<Feed> listFeed = new ArrayList<>();
for (Object l : objs){
if (l instanceof Feed)
listFeed.add((Feed)l);
}
return listFeed;
}
where the file contain something just like:
mypackage.Feed
mypackage.Subfeed
//and so on...
With Subfeed a subclass of feed.

How to define array of objects in a properties file and read from Java program

I have a properties file like this.
property[0].name=A
property[0].value=1
property[1].name=B
property[1].value=2
property[2].name=C
property[2].value=3
How to read this file as a list of objects of a class {name, value} in plain java program using ResourceBundle or Properties?
Here is the class.
public class XYZ {
private String name;
private String value;
// Getters & Setters
}
I need to get like this.
ArrayList<XYZ> propertiesList = SomeUtility.getProperties("property", XYZ.class);
Utility class might be like this.
public class SomeUtility {
public static ArrayList getProperties(String key, Class cls) {
//logic
}
}

I might not understand exactly what you want so feel free to correct me and give me more constraints to work with but here is a simple way to read a Properties file located somewhere in your project:
private static void readPropertiesFile(String path) throws IOException {
java.util.Map<String, String> map = new java.util.LinkedHashMap<>();
Properties properties = new Properties();
InputStream inputStream = new FileInputStream(path);
properties.load(inputStream);
for (String name : properties.stringPropertyNames()) {
map.put(name, properties.getProperty(name));
}
for (java.util.Map.Entry<String, String> entry : map.entrySet()) {
System.out.printf("Property Key: %s, Property Value: %s%n", entry.getKey(), entry.getValue());
}
}
Output
Property Key: property[0].name, Property Value: A
Property Key: property[1].name, Property Value: B
Property Key: property[0].value, Property Value: 1
Property Key: property[1].value, Property Value: 2
Property Key: property[2].name, Property Value: C
Property Key: property[2].value, Property Value: 3

This is the solution I wrote, but it involves Reflect and Gson. Is there any better way to do this? Anything already available which is fine tuned like Apache's.
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import java.lang.reflect.Field;
import java.util.*;
public class ListResourceBundle {
public static final Gson gson = new Gson();
private final ResourceBundle bundle;
public ListResourceBundle(ResourceBundle bundle) {
this.bundle = bundle;
}
public List<?> getProperties(String key, Class<?> cls) {
final int maxArraySize = getMaxArraySize(key, getMatchingKeys(key));
final List<String> fields = getFields(cls);
final List<Object> result = new ArrayList<>();
for (int i = 0; i < maxArraySize; i++) {
JsonObject jsonObject = new JsonObject();
for (String field : fields) {
jsonObject.addProperty(field, getStringOrNull(key + "[" + i + "]." + field));
}
result.add(gson.fromJson(jsonObject, cls));
}
System.out.println("result.toString() = " + result.toString());
return result;
}
public List<String> getMatchingKeys(String key) {
Enumeration<String> keys = bundle.getKeys();
List<String> matchingKeys = new ArrayList<>();
while(keys.hasMoreElements()) {
String k = keys.nextElement();
if(k.startsWith(key)) {
matchingKeys.add(k);
}
}
Collections.sort(matchingKeys);
return matchingKeys;
}
public int getMaxArraySize(String key, List<String> matchingKeys) {
int maxArraySize = 0;
for (int i = 0; ; i++) {
boolean indexAvailable = false;
for (String matchingKey : matchingKeys) {
if(matchingKey.startsWith(key + "[" + i + "]")) {
indexAvailable = true;
break;
}
}
if(indexAvailable) {
maxArraySize++;
} else {
break;
}
}
return maxArraySize;
}
public String getStringOrNull(String key) {
try {
return bundle.getString(key);
} catch (MissingResourceException e) {
return null;
}
}
public List<String> getFields(Class<?> cls) {
final List<String> fields = new ArrayList<>();
for (Field field : cls.getDeclaredFields()) {
fields.add(field.getName());
}
return fields;
}
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("com.example.application.resources.Resource");
ListResourceBundle applicationResourceBundle = new ListResourceBundle(bundle);
applicationResourceBundle.getProperties("property", ReportParam.class);
}
}
Resource:
property[0].name=A
property[0].value=1
property[1].name=B
property[1].value=2
property[2].name=C
property[2].value=3
Output:
result.toString() = [
ReportParam{name='A', value='1'},
ReportParam{name='B', value='2'},
ReportParam{name='C', value='3'}]
Process finished with exit code 0

I know it's bit late of an answer, but if I understand your problem statement correctly, you can use :
#ConfigurationProperties
to get your job done.
Here is my spring-boot example with a YAML file for the sake of convenience (same can be achieved through properties file as well).
application.yaml:
xyz:
xyzprops :
-
name: cbc
value: 441
-
name: obc
value: 443
XYZ class:
#Component
#ConfigurationProperties(prefix = "xyz")
public class XYZ{
private List<XYZProps> xyzprops;
public List<XYZProps> getXyzprops() {
return xyzprops;
}
public void setXyzprops(List<XYZProps> xyzprops) {
this.xyzprops = xyzprops;
}
public class XYZProps{
String name;
String value;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
}
And then #Autowire XYZ where you want to use it.

I would use JSON:
in your file:
property=[{"name":"A","value":"1"},{"name":"B","value":"2"},{"name":"C","value":"3"}]
and then deserialize it using com.google.gson.gson (or any other) library:
ArrayList<XYZ> propertiesList;
propertiesList = new gsonbuilder().create().fromjson(property, propertiesList.class);
NOTE: I haven't tested this code, and i'm not very familiar with java so i am sure there is a better,cleaner way to implement this.

Java Hibernate Transformer AliasToBeanNestedResultTransformer

i have a query like this. i pass the student ID i need some fields from Student as well as their parent as well some fields from the parent->Address[here is the main problem i am facing] i am using AliasToBeanNestedResultTransformer transformer by Sami Andoni
here is the implementation of it CODE
here is my code.
public List<Student>searchForStudent(Integer studentId)
{
Projection p=Projections.projectionList().create()
.add(Projections.property("name"),"name")//the student name it works O.K
.add(Projections.property("lastname"),"lastname")//the student name it works O.K
.add(Projections.property("age"),"age")//the student AGE it works O.K
.add(Projections.property("p.phone"),"parent.phone")//the parent phone it works O.K
.add(Projections.property("address.state").as("parent.Address.state")); // i need a field from address.state here is the problem...
Session session = ......
Criteria like = session.createCriteria(Student.class).add(prepareForSelect())//some filters..
.createAlias("parent","p")//the parent of the student. a student have one parent
.createAlias("parent.Address","address")//the address of the parent.... a parent have one address.
.setProjection(p)
.setResultTransformer(new AliasToBeanNestedResultTransformer(Student.class));
List<Student>results=like.list();
return results;
}
it throws
Exception in thread "main" org.hibernate.PropertyAccessException: IllegalArgumentException occurred while calling setter of com.generic.model.Parent.Address
FYI is some type mismatch i have done some tracing in SAMI code and i see this
[MyState]
[Address]
seems that Hibernate is returning a String State MyState in this case and the transformer is using a Address Object and this is the type Mismatch.
is any help is hugely needed it
thanks a lot.

I have improved the SamiAndoni class, maybe it solve your issue
package com.alutiiq.develop.promanagesys.core.util;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.hibernate.HibernateException;
import org.hibernate.property.PropertyAccessor;
import org.hibernate.property.PropertyAccessorFactory;
import org.hibernate.property.Setter;
import org.hibernate.transform.AliasToBeanResultTransformer;
import org.hibernate.transform.AliasedTupleSubsetResultTransformer;
import org.hibernate.transform.ResultTransformer;
/**
* Help to transform alises with nested alises
*
* #author Miguel Resendiz
*
*/
public class AliasToBeanNestedResultTransformer extends
AliasedTupleSubsetResultTransformer {
private static final long serialVersionUID = -8047276133980128266L;
private static final int TUPE_INDEX = 0;
private static final int ALISES_INDEX = 1;
private static final int FIELDNAME_INDEX = 2;
private static final PropertyAccessor accessor = PropertyAccessorFactory
.getPropertyAccessor("property");
private final Class<?> resultClass;
private Object[] entityTuples;
private String[] entityAliases;
private Map<String, Class<?>> fieldToClass = new HashMap<String, Class<?>>();
private Map<String, List<?>> subEntities = new HashMap<String, List<?>>();
private List<String> nestedAliases = new ArrayList<String>();
private Map<String, Class<?>> listFields = new HashMap<String, Class<?>>();
public boolean isTransformedValueATupleElement(String[] aliases,
int tupleLength) {
return false;
}
public AliasToBeanNestedResultTransformer(Class<?> resultClass) {
this.resultClass = resultClass;
}
public Object transformTuple(Object[] tuple, String[] aliases) {
handleSubEntities(tuple, aliases);
cleanParams(tuple, aliases);
ResultTransformer rootTransformer = new AliasToBeanResultTransformer(
resultClass);
Object root = rootTransformer.transformTuple(entityTuples,
entityAliases);
loadSubEntities(root);
cleanMaps();
return root;
}
private void handleSubEntities(Object[] tuple, String[] aliases)
throws HibernateException {
String fieldName = "";
String aliasName = "";
try {
for (int i = 0; i < aliases.length; i++) {
String alias = aliases[i];
if (alias.contains(".")) {
String[] sp = alias.split("\\.");
StringBuilder aliasBuilder = new StringBuilder();
for (int j = 0; j < sp.length; j++) {
if (j == 0) {
fieldName = sp[j];
} else {
aliasBuilder.append(sp[j]);
aliasBuilder.append(".");
}
}
aliasName = aliasBuilder.substring(0,
aliasBuilder.length() - 1);
nestedAliases.add(alias);
manageEntities(fieldName, aliasName, tuple[i]);
}
}
} catch (NoSuchFieldException e) {
throw new HibernateException("Could not instantiate resultclass: "
+ resultClass.getName() + " for field name: " + fieldName
+ " and alias name:" + aliasName);
}
}
private Class<?> findClass(String fieldName) throws NoSuchFieldException,
SecurityException {
if (fieldToClass.containsKey(fieldName)) {
return fieldToClass.get(fieldName);
} else {
Class<?> subclass = resultClass.getDeclaredField(fieldName)
.getType();
if (subclass.equals(List.class) || subclass.equals(Set.class)) {
if (subclass.equals(List.class)) {
listFields.put(fieldName, LinkedList.class);
} else {
listFields.put(fieldName, HashSet.class);
}
Field field = resultClass.getDeclaredField(fieldName);
ParameterizedType genericType = (ParameterizedType) field
.getGenericType();
subclass = (Class<?>) genericType.getActualTypeArguments()[0];
}
fieldToClass.put(fieldName, subclass);
return subclass;
}
}
#SuppressWarnings("unchecked")
private void manageEntities(String fieldName, String aliasName,
Object tupleValue) throws NoSuchFieldException, SecurityException {
Class<?> subclass = findClass(fieldName);
if (!subEntities.containsKey(fieldName)) {
List<Object> list = new ArrayList<Object>();
list.add(new ArrayList<Object>());
list.add(new ArrayList<String>());
list.add(FIELDNAME_INDEX, subclass);
subEntities.put(fieldName, list);
}
((List<Object>) subEntities.get(fieldName).get(TUPE_INDEX))
.add(tupleValue);
((List<String>) subEntities.get(fieldName).get(ALISES_INDEX))
.add(aliasName);
}
private void cleanParams(Object[] tuple, String[] aliases) {
entityTuples = new Object[aliases.length - nestedAliases.size()];
entityAliases = new String[aliases.length - nestedAliases.size()];
for (int j = 0, i = 0; j < aliases.length; j++) {
if (!nestedAliases.contains(aliases[j])) {
entityTuples[i] = tuple[j];
entityAliases[i] = aliases[j];
++i;
}
}
}
#SuppressWarnings({ "unchecked", "rawtypes" })
private void loadSubEntities(Object root) throws HibernateException {
try {
for (String fieldName : subEntities.keySet()) {
Class<?> subclass = (Class<?>) subEntities.get(fieldName).get(
FIELDNAME_INDEX);
ResultTransformer subclassTransformer = new AliasToBeanNestedResultTransformer(
subclass);
Object subObject = subclassTransformer.transformTuple(
((List<Object>) subEntities.get(fieldName).get(0))
.toArray(),
((List<Object>) subEntities.get(fieldName).get(1))
.toArray(new String[0]));
Setter setter = accessor.getSetter(resultClass, fieldName);
if (listFields.containsKey(fieldName)) {
Class<?> collectionClass = listFields.get(fieldName);
Collection subObjectList = (Collection) collectionClass
.newInstance();
subObjectList.add(subObject);
setter.set(root, subObjectList, null);
} else {
setter.set(root, subObject, null);
}
}
} catch (Exception e) {
throw new HibernateException(e);
}
}
private void cleanMaps() {
fieldToClass = new HashMap<String, Class<?>>();
subEntities = new HashMap<String, List<?>>();
nestedAliases = new ArrayList<String>();
listFields = new HashMap<String, Class<?>>();
}
}
I hope it help you.
--------------edit 07/25/15---------------
To group nested list.
public List<? extends Entity<?>> cleanList(
List<? extends Entity<?>> resultList) throws DataException {
List<Entity<?>> entities = new ArrayList<Entity<?>>();
Entity<?> current = null;
try {
for (Entity<?> entity : resultList) {
if (entity.getId() == null) {
continue;
}
if (current == null) {
current = entity;
continue;
}
if (current.getId().equals(entity.getId())) {
append(current, entity);
} else {
entities.add(current);
current = entity;
}
}
if (current != null) {
entities.add(current);
}
cleanSubList(entities);
return entities;
} catch (Exception e) {
throw new DataException(e);
}
}
#SuppressWarnings({ "rawtypes", "unchecked" })
public Set<? extends Entity<?>> cleanList(
Set<? extends Entity<?>> resultList) throws DataException {
List listToClean = new LinkedList();
listToClean.addAll(resultList);
listToClean = cleanList(listToClean);
resultList.clear();
resultList.addAll(listToClean);
return resultList;
}
#SuppressWarnings({ "unchecked", "rawtypes" })
private void append(Entity<?> current, Entity<?> next)
throws IllegalArgumentException, IllegalAccessException {
Field[] fields = current.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.getType().equals(List.class)) {
field.setAccessible(true);
List valueNext = (List) field.get(next);
List valueCurrent = (List) field.get(current);
if (valueNext != null) {
if (valueCurrent != null) {
valueCurrent.addAll(valueNext);
field.set(current, valueCurrent);
} else {
field.set(current, valueNext);
}
}
} else if (field.getType().equals(Set.class)) {
field.setAccessible(true);
Set valueNext = (Set) field.get(next);
Set valueCurrent = (Set) field.get(current);
if (valueNext != null) {
if (valueCurrent != null) {
valueCurrent.addAll(valueNext);
field.set(current, valueCurrent);
} else {
field.set(current, valueNext);
}
}
}
}
}
#SuppressWarnings({ "rawtypes", "unchecked" })
private void cleanSubList(List<? extends Entity<?>> listToClean)
throws IllegalArgumentException, IllegalAccessException,
DataException {
for (Entity<?> entity : listToClean) {
Field[] fields = entity.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.getType().equals(List.class)) {
field.setAccessible(true);
List valueToClean = (List) field.get(entity);
// Throw a thread
if (valueToClean != null) {
valueToClean = cleanList(valueToClean);
field.set(entity, valueToClean);
}
} else if (field.getType().equals(Set.class)) {
field.setAccessible(true);
Set valueToClean = (Set) field.get(entity);
// Throw a thread
if (valueToClean != null) {
valueToClean = cleanList(valueToClean);
field.set(entity, valueToClean);
}
}
}
}
}
To speed up the process I´m suggesting throw a thread in the main process.
This is my Entity interface:
package com.alutiiq.develop.promanagesys.common.entity;
import java.io.Serializable;
/**
* Entity for Hibernate comunications
*
* #author Miguel Resendiz
*
* #param <I>
* Primary key type
*/
public interface Entity<I extends Serializable> extends Serializable {
/**
* Enable poissibility to write generic queries using primary key
*
* #return primary key value for entity
*/
I getId();
void setId(I id);
void setId(String id);
}
Usage example:
criteria.setResultTransformer(new AliasToBeanNestedResultTransformer(
entityClass));
List<Project> projects = criteria.list();
projects = (List<Project>) cleanList(projects);

Java Reflection to set Value for the java pojo

Goal :
set value for the given java bean at run time and generate JSON Object or JSON array.
the above is my goal and i have tried some thing like the below :
package com.hexgen.tools;
import java.lang.reflect.Method;
import com.google.gson.Gson;
public class ConvertPOJOToJSON {
public Object creatJSONObject(String className) throws IllegalArgumentException, IllegalAccessException, InstantiationException, Exception {
Class<?> objectClass = null;
Object clsObject =null;
try {
objectClass = Class.forName(className);
clsObject = objectClass.newInstance();
for(Method m : objectClass.getMethods())
if (m.getName().startsWith("set") && m.getParameterTypes().length == 1 && m.getModifiers()==23)
m.invoke(clsObject, "myValue");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return clsObject;
}
public static void main(String[] args) {
Gson gson = new Gson();
ConvertPOJOToJSON pojoToJSON = new ConvertPOJOToJSON();
try {
System.out.println("JSON OBJECT : "+gson.toJson(pojoToJSON.creatJSONObject("com.hexgen.ro.request.CreateRequisitionRO")));
} catch (Exception e) {
e.printStackTrace();
}
}
}
The Output of the above class :
JSON OBJECT : {"isAllocable":false}
there are many fields in the class i gave com.hexgen.ro.request.CreateRequisitionRO but only one boolean value is set to false and returns the value.
i have some constant value to set for the fields say if the field type is Integer than set some default integer value like so
EDIT :
I have created a enum like the following :
package com.hexgen.tools;
import java.math.BigDecimal;
import java.math.BigInteger;
import org.joda.time.LocalDate;
public enum DefaultParamValues {
STRING("HEXGEN"),
INTEGER(123),
DATE(new LocalDate()),
BOOLEAN(true),
LONGVALUE(123123),
BIGDECIMAL(new BigDecimal("100000"));
private String defaultString;
private int defaultInteger;
private LocalDate defaultDate;
private boolean defaultBoolean;
private long defaultLong;
private BigDecimal defaultBigDecimal;
private DefaultParamValues(String strDefaultValue) {
defaultString = strDefaultValue;
}
private DefaultParamValues(int intDefaultValue) {
defaultInteger = intDefaultValue;
}
private DefaultParamValues(LocalDate dateDefaultValue) {
defaultDate = dateDefaultValue;
}
private DefaultParamValues(boolean booleanDefaultValue) {
defaultBoolean = booleanDefaultValue;
}
private DefaultParamValues(long longDefaultValue) {
defaultLong = longDefaultValue;
}
private DefaultParamValues(BigDecimal bigIntegerDefaultValue) {
defaultBigDecimal = bigIntegerDefaultValue;
}
public String getDefaultString() {
return defaultString;
}
public int getDefaultInt() {
return defaultInteger;
}
public LocalDate getDefaultDate() {
return defaultDate;
}
public boolean getDefaultBoolean() {
return defaultBoolean;
}
public long getDefaultLong() {
return defaultLong;
}
public BigDecimal getDdefaultBigDecimal() {
return defaultBigDecimal;
}
}
created one more method like the following :
public Object creatObjectWithDefaultValue(String className) throws IllegalArgumentException, IllegalAccessException, InstantiationException {
DefaultParamValues defaultParamValues = null;
Class<?> objectClass = null;
Object clsObject =null;
try {
objectClass = Class.forName(className);
clsObject = objectClass.newInstance();
Field[] fields = objectClass.getDeclaredFields();
for(Field f:fields){
if(!f.isAccessible()){
f.setAccessible(true);
Class<?> type = f.getType();
if(! Modifier.isFinal(f.getModifiers()) && type.equals(Integer.class)){
f.set(clsObject, defaultParamValues.INTEGER);
} else if( !Modifier.isFinal(f.getModifiers()) && type.equals(java.math.BigDecimal.class)){
f.set(clsObject, defaultParamValues.BIGDECIMAL);
} else if(! Modifier.isFinal(f.getModifiers()) && type.equals(org.joda.time.LocalDate.class)){
f.set(clsObject,defaultParamValues.DATE);
} else if(! Modifier.isFinal(f.getModifiers()) && type.equals(boolean.class)){
f.set(clsObject, defaultParamValues.BOOLEAN);
} else if(! Modifier.isFinal(f.getModifiers()) && type.equals(java.lang.String.class)){
f.set(clsObject, defaultParamValues.STRING);
}
else if(! Modifier.isFinal(f.getModifiers()) && type.equals(long.class)){
f.set(clsObject, defaultParamValues.LONGVALUE);
}
//f.setAccessible(false);
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return clsObject;
}
to set the default values but i get the following exception:
Exception in thread "main" java.lang.IllegalArgumentException: Can not set java.math.BigDecimal field com.hexgen.ro.request.CreateRequisitionRO.transSrlNo to com.hexgen.tools.DefaultParamValues
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:146)
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:150)
at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:63)
at java.lang.reflect.Field.set(Field.java:657)
at com.hexgen.tools.JsonConverter.creatObjectWithDefaultValue(JsonConverter.java:93)
at com.hexgen.tools.JsonConverter.main(JsonConverter.java:201)
Please help me to find the solution.
Best Regards

If your looking for a lightweight library which can do this and more including allowing you to do your own filtering to find Methods/Fields. I wrote an open source library which has no 3rd party dependencies and is available on Maven Central.
Checkout https://github.com/gondor/reflect
As for your issue it appears your setting the "Enum" constant and not the inner value of the enum. Wouldn't it DefaultParamValues.BIGDECIMAL.getDdefaultBigDecimal()

Printing all variables value from a class

I have a class with information about a Person that looks something like this:
public class Contact {
private String name;
private String location;
private String address;
private String email;
private String phone;
private String fax;
public String toString() {
// Something here
}
// Getters and setters.
}
I want toString() to return this.name +" - "+ this.locations + ... for all variables. I was trying to implement it using reflection as shown from this question but I can't manage to print instance variables.
What is the correct way to solve this?

From Implementing toString:
public String toString() {
StringBuilder result = new StringBuilder();
String newLine = System.getProperty("line.separator");
result.append( this.getClass().getName() );
result.append( " Object {" );
result.append(newLine);
//determine fields declared in this class only (no fields of superclass)
Field[] fields = this.getClass().getDeclaredFields();
//print field names paired with their values
for ( Field field : fields ) {
result.append(" ");
try {
result.append( field.getName() );
result.append(": ");
//requires access to private field:
result.append( field.get(this) );
} catch ( IllegalAccessException ex ) {
System.out.println(ex);
}
result.append(newLine);
}
result.append("}");
return result.toString();
}

Why do you want to reinvent the wheel when there are opensource that are already doing the job pretty nicely.
Both apache common-langs and spring support some very flexible builder pattern
For apache, here is how you do it reflectively
#Override
public String toString()
{
return ToStringBuilder.reflectionToString(this);
}
Here is how you do it if you only want to print fields that you care about.
#Override
public String toString()
{
return new ToStringBuilder(this)
.append("name", name)
.append("location", location)
.append("address", address)
.toString();
}
You can go as far as "styling" your print output with non-default ToStringStyle or even customizing it with your own style.
I didn't personally try spring ToStringCreator api, but it looks very similar.

If you are using Eclipse, this should be easy:
1.Press Alt+Shift+S
2.Choose "Generate toString()..."
Enjoy! You can have any template of toString()s.
This also works with getter/setters.

Generic toString() one-liner, using reflection and style customization:
import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;
...
public String toString()
{
return ReflectionToStringBuilder.toString(this, ToStringStyle.SHORT_PREFIX_STYLE);
}

When accessing the field value, pass the instance rather than null.
Why not use code generation here? Eclipse, for example, will generate a reasoble toString implementation for you.

Another simple approach is to let Lombok generate the toString method for you.
For this:
Simply add Lombok to your project
Add the annotation #ToString to the definition of your class
Compile your class/project, and it is done
So for example in your case, your class would look like this:
#ToString
public class Contact {
private String name;
private String location;
private String address;
private String email;
private String phone;
private String fax;
// Getters and setters.
}
Example of output in this case:
Contact(name=John, location=USA, address=SF, email=foo#bar.com, phone=99999, fax=88888)
More details about how to use the annotation #ToString.
NB: You can also let Lombok generate the getters and setters for you, here is the full feature list.

If the output from ReflectionToStringBuilder.toString() is not enough readable for you, here is code that:
1) sorts field names alphabetically
2) flags non-null fields with asterisks in the beginning of the line
public static Collection<Field> getAllFields(Class<?> type) {
TreeSet<Field> fields = new TreeSet<Field>(
new Comparator<Field>() {
#Override
public int compare(Field o1, Field o2) {
int res = o1.getName().compareTo(o2.getName());
if (0 != res) {
return res;
}
res = o1.getDeclaringClass().getSimpleName().compareTo(o2.getDeclaringClass().getSimpleName());
if (0 != res) {
return res;
}
res = o1.getDeclaringClass().getName().compareTo(o2.getDeclaringClass().getName());
return res;
}
});
for (Class<?> c = type; c != null; c = c.getSuperclass()) {
fields.addAll(Arrays.asList(c.getDeclaredFields()));
}
return fields;
}
public static void printAllFields(Object obj) {
for (Field field : getAllFields(obj.getClass())) {
field.setAccessible(true);
String name = field.getName();
Object value = null;
try {
value = field.get(obj);
} catch (IllegalArgumentException | IllegalAccessException e) {
e.printStackTrace();
}
System.out.printf("%s %s.%s = %s;\n", value==null?" ":"*", field.getDeclaringClass().getSimpleName(), name, value);
}
}
test harness:
public static void main(String[] args) {
A a = new A();
a.x = 1;
B b = new B();
b.x=10;
b.y=20;
System.out.println("=======");
printAllFields(a);
System.out.println("=======");
printAllFields(b);
System.out.println("=======");
}
class A {
int x;
String z = "z";
Integer b;
}
class B extends A {
int y;
private double z = 12345.6;
public int a = 55;
}

Addition with #cletus answer, You have to fetch all model fields(upper hierarchy) and set field.setAccessible(true) to access private members. Here is the full snippet:
#Override
public String toString() {
StringBuilder result = new StringBuilder();
String newLine = System.getProperty("line.separator");
result.append(getClass().getSimpleName());
result.append( " {" );
result.append(newLine);
List<Field> fields = getAllModelFields(getClass());
for (Field field : fields) {
result.append(" ");
try {
result.append(field.getName());
result.append(": ");
field.setAccessible(true);
result.append(field.get(this));
} catch ( IllegalAccessException ex ) {
// System.err.println(ex);
}
result.append(newLine);
}
result.append("}");
result.append(newLine);
return result.toString();
}
private List<Field> getAllModelFields(Class aClass) {
List<Field> fields = new ArrayList<>();
do {
Collections.addAll(fields, aClass.getDeclaredFields());
aClass = aClass.getSuperclass();
} while (aClass != null);
return fields;
}

i will get my answer as follow:
import java.io.IOException;
import java.io.Writer;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
public class findclass {
public static void main(String[] args) throws Exception, IllegalAccessException {
new findclass().findclass(new Object(), "objectName");
new findclass().findclass(1213, "int");
new findclass().findclass("ssdfs", "String");
}
public Map<String, String>map=new HashMap<String, String>();
public void findclass(Object c,String name) throws IllegalArgumentException, IllegalAccessException {
if(map.containsKey(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()))){
System.out.println(c.getClass().getSimpleName()+" "+name+" = "+map.get(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()))+" = "+c);
return;}
map.put(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()), name);
Class te=c.getClass();
if(te.equals(Integer.class)||te.equals(Double.class)||te.equals(Float.class)||te.equals(Boolean.class)||te.equals(Byte.class)||te.equals(Long.class)||te.equals(String.class)||te.equals(Character.class)){
System.out.println(c.getClass().getSimpleName()+" "+name+" = "+c);
return;
}
if(te.isArray()){
if(te==int[].class||te==char[].class||te==double[].class||te==float[].class||te==byte[].class||te==long[].class||te==boolean[].class){
boolean dotflag=true;
for (int i = 0; i < Array.getLength(c); i++) {
System.out.println(Array.get(c, i).getClass().getSimpleName()+" "+name+"["+i+"] = "+Array.get(c, i));
}
return;
}
Object[]arr=(Object[])c;
for (Object object : arr) {
if(object==null)
System.out.println(c.getClass().getSimpleName()+" "+name+" = null");
else {
findclass(object, name+"."+object.getClass().getSimpleName());
}
}
}
Field[] fields=c.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
if(field.get(c)==null){
System.out.println(field.getType().getSimpleName()+" "+name+"."+field.getName()+" = null");
continue;
}
findclass(field.get(c),name+"."+field.getName());
}
if(te.getSuperclass()==Number.class||te.getSuperclass()==Object.class||te.getSuperclass()==null)
return;
Field[]faFields=c.getClass().getSuperclass().getDeclaredFields();
for (Field field : faFields) {
field.setAccessible(true);
if(field.get(c)==null){
System.out.println(field.getType().getSimpleName()+" "+name+"<"+c.getClass().getSuperclass().getSimpleName()+"."+field.getName()+" = null");
continue;
}
Object check=field.get(c);
findclass(field.get(c),name+"<"+c.getClass().getSuperclass().getSimpleName()+"."+field.getName());
}
}
public void findclass(Object c,String name,Writer writer) throws IllegalArgumentException, IllegalAccessException, IOException {
if(map.containsKey(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()))){
writer.append(c.getClass().getSimpleName()+" "+name+" = "+map.get(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()))+" = "+c+"\n");
return;}
map.put(c.getClass().getName() + "#" + Integer.toHexString(c.hashCode()), name);
Class te=c.getClass();
if(te.equals(Integer.class)||te.equals(Double.class)||te.equals(Float.class)||te.equals(Boolean.class)||te.equals(Byte.class)||te.equals(Long.class)||te.equals(String.class)||te.equals(Character.class)){
writer.append(c.getClass().getSimpleName()+" "+name+" = "+c+"\n");
return;
}
if(te.isArray()){
if(te==int[].class||te==char[].class||te==double[].class||te==float[].class||te==byte[].class||te==long[].class||te==boolean[].class){
boolean dotflag=true;
for (int i = 0; i < Array.getLength(c); i++) {
writer.append(Array.get(c, i).getClass().getSimpleName()+" "+name+"["+i+"] = "+Array.get(c, i)+"\n");
}
return;
}
Object[]arr=(Object[])c;
for (Object object : arr) {
if(object==null){
writer.append(c.getClass().getSimpleName()+" "+name+" = null"+"\n");
}else {
findclass(object, name+"."+object.getClass().getSimpleName(),writer);
}
}
}
Field[] fields=c.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
if(field.get(c)==null){
writer.append(field.getType().getSimpleName()+" "+name+"."+field.getName()+" = null"+"\n");
continue;
}
findclass(field.get(c),name+"."+field.getName(),writer);
}
if(te.getSuperclass()==Number.class||te.getSuperclass()==Object.class||te.getSuperclass()==null)
return;
Field[]faFields=c.getClass().getSuperclass().getDeclaredFields();
for (Field field : faFields) {
field.setAccessible(true);
if(field.get(c)==null){
writer.append(field.getType().getSimpleName()+" "+name+"<"+c.getClass().getSuperclass().getSimpleName()+"."+field.getName()+" = null"+"\n");
continue;
}
Object check=field.get(c);
findclass(field.get(c),name+"<"+c.getClass().getSuperclass().getSimpleName()+"."+field.getName(),writer);
}
}
}