[flexcoders] Re: Trouble Converting java List to ArrayCollection
I believe anything implementing java.util.Collection, such as List, is
already being converted to an ArrayCollection on the Flex side.
http://livedocs.macromedia.com/flex/2/docs/1104.html#270405
http://livedocs.macromedia.com/flex/2/docs/1104.html#270405
In your result handler, try:
var col:ArrayCollection = re.result as ArrayCollection;
--- In flexcoders@yahoogroups.com, ytseshred [EMAIL PROTECTED] wrote:
I'm using RemoteObjects to connect to my backend. In one of my calls
I'm trying to return a List of VO's I create after hitting my
database.
On the Flex side, my result event is firing properly, but when I try
to convert the result to an ArrayCollection, instead of getting a
proper ArrayCollection I get single element that displays the
following when I output it in an alert: obj is: '[object TestVO],
[object TestVO], ... [object TestVO]'.
If I return a single TestVO object directly instead of a List, I can
properly cast the result to my ActionScript TestVO object and view the
data properly. It's just returning the List that's giving me problems.
Can anyone offer any suggestions please?
My Flex result code is:
public function result(evt:Object):void {
if(evt.type evt.type == ResultEvent.RESULT) {
var re:ResultEvent = evt as ResultEvent;
var col:ArrayCollection = new
ArrayCollection(ArrayUtil.toArray(re.result));
if(col) {
Alert.show(obj is: ' + col.getItemAt(0) + ');
}
else Alert.show(Didn't cast properly!);
}
}
My Java DAO code that returns the list is:
public List getList() throws DAOException {
List list = new ArrayList();
Connection c = null;
try {
c = ConnectionHelper.getConnection();
Statement s = c.createStatement();
ResultSet rs = s.executeQuery(SELECT * FROM test);
while(rs.next()) {
TestVO vo = new TestVO();
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
list.add(vo);
}
} catch(Exception e) {
e.printStackTrace();
throw new DAOException(e);
} finally {
ConnectionHelper.close(c);
}
return list;
}
[flexcoders] Re: Trouble Converting java List to ArrayCollection
Thanks, the casting directly to ArrayCollection using as did work. I
was doing this initially, and then made some other changes to get rid
of another error and forgot to change back.
Andre, this isn't production code and I got it off of Cristophe's
TestDriver server
(http://coenraets.org/blog/2007/01/flex-data-management-services-tutorial/)
but thanks for pointing this out.
--- In flexcoders@yahoogroups.com, André Rodrigues Pena
[EMAIL PROTECTED] wrote:
Man.. Just remove the throws of your getList() method. Never use
throws at a
service method. (specially in this example where the throws is USELESS
because you are already treating the exception with the try clause) The
throws clause passes the exception treatment to a higher scope, this
scope
may not import de DAOException needed to process it properly. Simply
never
do this.
On 2/12/07, ytseshred [EMAIL PROTECTED] wrote:
I'm using RemoteObjects to connect to my backend. In one of my calls
I'm trying to return a List of VO's I create after hitting my
database.
On the Flex side, my result event is firing properly, but when I try
to convert the result to an ArrayCollection, instead of getting a
proper ArrayCollection I get single element that displays the
following when I output it in an alert: obj is: '[object TestVO],
[object TestVO], ... [object TestVO]'.
If I return a single TestVO object directly instead of a List, I can
properly cast the result to my ActionScript TestVO object and view the
data properly. It's just returning the List that's giving me problems.
Can anyone offer any suggestions please?
My Flex result code is:
public function result(evt:Object):void {
if(evt.type evt.type == ResultEvent.RESULT) {
var re:ResultEvent = evt as ResultEvent;
var col:ArrayCollection = new
ArrayCollection(ArrayUtil.toArray(re.result));
if(col) {
Alert.show(obj is: ' + col.getItemAt(0) + ');
}
else Alert.show(Didn't cast properly!);
}
}
My Java DAO code that returns the list is:
public List getList() throws DAOException {
List list = new ArrayList();
Connection c = null;
try {
c = ConnectionHelper.getConnection();
Statement s = c.createStatement();
ResultSet rs = s.executeQuery(SELECT * FROM test);
while(rs.next()) {
TestVO vo = new TestVO();
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
list.add(vo);
}
} catch(Exception e) {
e.printStackTrace();
throw new DAOException(e);
} finally {
ConnectionHelper.close(c);
}
return list;
}
--
André Rodrigues Pena
LOCUS
www.locus.com.br
Blog
www.techbreak.org
[flexcoders] Re: Trouble Converting java List to ArrayCollection
I have to disagree about not throwing the Exception. If you actually
handle the exception in the method then you shouldn't throw it, but
the exception is not being handled. The user needs to know that
something went wrong. And the bit about the Higher scope not importing
the DAOException, that's just plain wrong. The higher scope will see
it as an Exception if it doesn't handle the specific Exception. Not
throwing the exception will simply return an empty list.
The real question is what is the Exception that is being thrown in the
try block? That will tell us what the issue is and lead us to the
conclusion as to how to fix it. Is there a Stack Trace available that
I can look at?
Also...
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
... this is bad from. You shouldn't be accessing data members
directly, they should be encapsulated, and you should access them
using accesser methods.
Paul
--- In flexcoders@yahoogroups.com, André Rodrigues Pena
[EMAIL PROTECTED] wrote:
Man.. Just remove the throws of your getList() method. Never use
throws at a
service method. (specially in this example where the throws is USELESS
because you are already treating the exception with the try clause) The
throws clause passes the exception treatment to a higher scope, this
scope
may not import de DAOException needed to process it properly. Simply
never
do this.
On 2/12/07, ytseshred [EMAIL PROTECTED] wrote:
I'm using RemoteObjects to connect to my backend. In one of my calls
I'm trying to return a List of VO's I create after hitting my
database.
On the Flex side, my result event is firing properly, but when I try
to convert the result to an ArrayCollection, instead of getting a
proper ArrayCollection I get single element that displays the
following when I output it in an alert: obj is: '[object TestVO],
[object TestVO], ... [object TestVO]'.
If I return a single TestVO object directly instead of a List, I can
properly cast the result to my ActionScript TestVO object and view the
data properly. It's just returning the List that's giving me problems.
Can anyone offer any suggestions please?
My Flex result code is:
public function result(evt:Object):void {
if(evt.type evt.type == ResultEvent.RESULT) {
var re:ResultEvent = evt as ResultEvent;
var col:ArrayCollection = new
ArrayCollection(ArrayUtil.toArray(re.result));
if(col) {
Alert.show(obj is: ' + col.getItemAt(0) + ');
}
else Alert.show(Didn't cast properly!);
}
}
My Java DAO code that returns the list is:
public List getList() throws DAOException {
List list = new ArrayList();
Connection c = null;
try {
c = ConnectionHelper.getConnection();
Statement s = c.createStatement();
ResultSet rs = s.executeQuery(SELECT * FROM test);
while(rs.next()) {
TestVO vo = new TestVO();
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
list.add(vo);
}
} catch(Exception e) {
e.printStackTrace();
throw new DAOException(e);
} finally {
ConnectionHelper.close(c);
}
return list;
}
--
André Rodrigues Pena
LOCUS
www.locus.com.br
Blog
www.techbreak.org
[flexcoders] Re: Trouble Converting java List to ArrayCollection
That was a typo on my Part. They are being set using methods:
TestVO vo = new TestVO();
vo.setID(rs.getInt(id));
vo.setData(rs.getString(data));
The problem has been solved by casting the result to ArrayCollection
using the as keyword.
I'm not sure what was causing my first problem, but I originally had
my VO's defined with constructors, so I could create the VO like:
TestVO vo = new TestVO(rs.getInt(id), rs.getString(data));
But Flex gave a runtime error when it was constructing the array
collection saying something like TestVO init expected 2 arguments and
got 0.
--- In flexcoders@yahoogroups.com, lepusmars [EMAIL PROTECTED] wrote:
I have to disagree about not throwing the Exception. If you actually
handle the exception in the method then you shouldn't throw it, but
the exception is not being handled. The user needs to know that
something went wrong. And the bit about the Higher scope not importing
the DAOException, that's just plain wrong. The higher scope will see
it as an Exception if it doesn't handle the specific Exception. Not
throwing the exception will simply return an empty list.
The real question is what is the Exception that is being thrown in the
try block? That will tell us what the issue is and lead us to the
conclusion as to how to fix it. Is there a Stack Trace available that
I can look at?
Also...
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
... this is bad from. You shouldn't be accessing data members
directly, they should be encapsulated, and you should access them
using accesser methods.
Paul
--- In flexcoders@yahoogroups.com, André Rodrigues Pena
andre.ufrj@ wrote:
Man.. Just remove the throws of your getList() method. Never use
throws at a
service method. (specially in this example where the throws is USELESS
because you are already treating the exception with the try
clause) The
throws clause passes the exception treatment to a higher scope, this
scope
may not import de DAOException needed to process it properly. Simply
never
do this.
On 2/12/07, ytseshred ytseshred@ wrote:
I'm using RemoteObjects to connect to my backend. In one of my
calls
I'm trying to return a List of VO's I create after hitting my
database.
On the Flex side, my result event is firing properly, but when I try
to convert the result to an ArrayCollection, instead of getting a
proper ArrayCollection I get single element that displays the
following when I output it in an alert: obj is: '[object TestVO],
[object TestVO], ... [object TestVO]'.
If I return a single TestVO object directly instead of a List, I can
properly cast the result to my ActionScript TestVO object and
view the
data properly. It's just returning the List that's giving me
problems.
Can anyone offer any suggestions please?
My Flex result code is:
public function result(evt:Object):void {
if(evt.type evt.type == ResultEvent.RESULT) {
var re:ResultEvent = evt as ResultEvent;
var col:ArrayCollection = new
ArrayCollection(ArrayUtil.toArray(re.result));
if(col) {
Alert.show(obj is: ' + col.getItemAt(0) + ');
}
else Alert.show(Didn't cast properly!);
}
}
My Java DAO code that returns the list is:
public List getList() throws DAOException {
List list = new ArrayList();
Connection c = null;
try {
c = ConnectionHelper.getConnection();
Statement s = c.createStatement();
ResultSet rs = s.executeQuery(SELECT * FROM test);
while(rs.next()) {
TestVO vo = new TestVO();
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
list.add(vo);
}
} catch(Exception e) {
e.printStackTrace();
throw new DAOException(e);
} finally {
ConnectionHelper.close(c);
}
return list;
}
--
André Rodrigues Pena
LOCUS
www.locus.com.br
Blog
www.techbreak.org
[flexcoders] Re: Trouble Converting java List to ArrayCollection
Another way is:
if(re.result is ArrayCollection) {
var col:ArrayCollection = ArrayCollection(re.result);
}
The as operation is more brief but accomplishes the same thing. as
will leave your object as null, where as doing the is check you can
catch potential errors and not create any unnecessary objects. I don't
think either way is more right or wrong.
--- In flexcoders@yahoogroups.com, ytseshred [EMAIL PROTECTED] wrote:
That was a typo on my Part. They are being set using methods:
TestVO vo = new TestVO();
vo.setID(rs.getInt(id));
vo.setData(rs.getString(data));
The problem has been solved by casting the result to ArrayCollection
using the as keyword.
I'm not sure what was causing my first problem, but I originally had
my VO's defined with constructors, so I could create the VO like:
TestVO vo = new TestVO(rs.getInt(id), rs.getString(data));
But Flex gave a runtime error when it was constructing the array
collection saying something like TestVO init expected 2 arguments and
got 0.
[flexcoders] Re: Trouble Converting java List to ArrayCollection
Flex wants a public constructor with no arguments available, so the
solution is to just add your second constructor with whatever
arguments you want while keeping the default constructor. That
would make both of the folowing valid:
TestVO vo = new TestVO();
TestVO vo = new TestVO(rs.getInt(id), rs.getString(data));
It may arguably be bad form to access data members directly, but
strict adherence to good Java form in value objects just leads to
problems on the Flex side. If, for example, you went the full route
and declared your data members private to force the use of accessor
methods, your Flex object would contain no properties since Flex
would have no visibility to the private members. I usually just let
it slide, and create a Java good form wrapper object if I must for
accessing on the server side.
Doug
--- In flexcoders@yahoogroups.com, ytseshred [EMAIL PROTECTED] wrote:
That was a typo on my Part. They are being set using methods:
TestVO vo = new TestVO();
vo.setID(rs.getInt(id));
vo.setData(rs.getString(data));
The problem has been solved by casting the result to
ArrayCollection
using the as keyword.
I'm not sure what was causing my first problem, but I originally
had
my VO's defined with constructors, so I could create the VO like:
TestVO vo = new TestVO(rs.getInt(id), rs.getString(data));
But Flex gave a runtime error when it was constructing the array
collection saying something like TestVO init expected 2 arguments
and
got 0.
--- In flexcoders@yahoogroups.com, lepusmars paul@ wrote:
I have to disagree about not throwing the Exception. If you
actually
handle the exception in the method then you shouldn't throw it,
but
the exception is not being handled. The user needs to know that
something went wrong. And the bit about the Higher scope not
importing
the DAOException, that's just plain wrong. The higher scope
will see
it as an Exception if it doesn't handle the specific Exception.
Not
throwing the exception will simply return an empty list.
The real question is what is the Exception that is being thrown
in the
try block? That will tell us what the issue is and lead us to
the
conclusion as to how to fix it. Is there a Stack Trace
available that
I can look at?
Also...
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
... this is bad from. You shouldn't be accessing data members
directly, they should be encapsulated, and you should access them
using accesser methods.
Paul
--- In flexcoders@yahoogroups.com, André Rodrigues Pena
andre.ufrj@ wrote:
Man.. Just remove the throws of your getList() method. Never
use
throws at a
service method. (specially in this example where the throws is
USELESS
because you are already treating the exception with the try
clause) The
throws clause passes the exception treatment to a higher
scope, this
scope
may not import de DAOException needed to process it properly.
Simply
never
do this.
On 2/12/07, ytseshred ytseshred@ wrote:
I'm using RemoteObjects to connect to my backend. In one
of my
calls
I'm trying to return a List of VO's I create after hitting my
database.
On the Flex side, my result event is firing properly, but
when I try
to convert the result to an ArrayCollection, instead of
getting a
proper ArrayCollection I get single element that displays the
following when I output it in an alert: obj is: '[object
TestVO],
[object TestVO], ... [object TestVO]'.
If I return a single TestVO object directly instead of a
List, I can
properly cast the result to my ActionScript TestVO object and
view the
data properly. It's just returning the List that's giving me
problems.
Can anyone offer any suggestions please?
My Flex result code is:
public function result(evt:Object):void {
if(evt.type evt.type == ResultEvent.RESULT) {
var re:ResultEvent = evt as ResultEvent;
var col:ArrayCollection = new
ArrayCollection(ArrayUtil.toArray(re.result));
if(col) {
Alert.show(obj is: ' + col.getItemAt(0) + ');
}
else Alert.show(Didn't cast properly!);
}
}
My Java DAO code that returns the list is:
public List getList() throws DAOException {
List list = new ArrayList();
Connection c = null;
try {
c = ConnectionHelper.getConnection();
Statement s = c.createStatement();
ResultSet rs = s.executeQuery(SELECT * FROM test);
while(rs.next()) {
TestVO vo = new TestVO();
vo.id = rs.getInt(id);
vo.data = rs.getString(data);
list.add(vo);
}
} catch(Exception e) {
e.printStackTrace();
throw new DAOException(e);
} finally {
ConnectionHelper.close(c);
}
return list;
}
--
André Rodrigues Pena
LOCUS
www.locus.com.br
Blog
www.techbreak.org
[flexcoders] Re: Trouble Converting java List to ArrayCollection
I think you misinterpreted, the TestVO is a java class. Coding it correctly should not affect the Flex versions of the class. When the bean is transfered to Flex it will contain publicly accessable properties representing the private members that have public getters, ie if you have getData there will be a property data on the transfered object. That is how Java Beans work. If this convention is not followed then if you start working with Enterprise level projects you run into problems. --- In flexcoders@yahoogroups.com, Doug Lowder [EMAIL PROTECTED] wrote: Flex wants a public constructor with no arguments available, so the solution is to just add your second constructor with whatever arguments you want while keeping the default constructor. That would make both of the folowing valid: TestVO vo = new TestVO(); TestVO vo = new TestVO(rs.getInt(id), rs.getString(data)); It may arguably be bad form to access data members directly, but strict adherence to good Java form in value objects just leads to problems on the Flex side. If, for example, you went the full route and declared your data members private to force the use of accessor methods, your Flex object would contain no properties since Flex would have no visibility to the private members. I usually just let it slide, and create a Java good form wrapper object if I must for accessing on the server side. Doug --- In flexcoders@yahoogroups.com, ytseshred ytseshred@ wrote: That was a typo on my Part. They are being set using methods: TestVO vo = new TestVO(); vo.setID(rs.getInt(id)); vo.setData(rs.getString(data)); The problem has been solved by casting the result to ArrayCollection using the as keyword. I'm not sure what was causing my first problem, but I originally had my VO's defined with constructors, so I could create the VO like: TestVO vo = new TestVO(rs.getInt(id), rs.getString(data)); But Flex gave a runtime error when it was constructing the array collection saying something like TestVO init expected 2 arguments and got 0.
[flexcoders] Re: Trouble Converting java List to ArrayCollection
Nope, I didn't misinterpret. I know TestVO is a Java class (probably with a Flex counterpart class), and the way the Java class is coded can definitely have an effect when it is accessed from Flex. It isn't a case of correctness, but a case of what Flex expects from Java classes. You can test this all out yourself by implementing multiple constructors and/or declaring the properties as private in your Java class. Best, Doug --- In flexcoders@yahoogroups.com, lepusmars [EMAIL PROTECTED] wrote: I think you misinterpreted, the TestVO is a java class. Coding it correctly should not affect the Flex versions of the class. When the bean is transfered to Flex it will contain publicly accessable properties representing the private members that have public getters, ie if you have getData there will be a property data on the transfered object. That is how Java Beans work. If this convention is not followed then if you start working with Enterprise level projects you run into problems. --- In flexcoders@yahoogroups.com, Doug Lowder douglowder@ wrote: Flex wants a public constructor with no arguments available, so the solution is to just add your second constructor with whatever arguments you want while keeping the default constructor. That would make both of the folowing valid: TestVO vo = new TestVO(); TestVO vo = new TestVO(rs.getInt(id), rs.getString(data)); It may arguably be bad form to access data members directly, but strict adherence to good Java form in value objects just leads to problems on the Flex side. If, for example, you went the full route and declared your data members private to force the use of accessor methods, your Flex object would contain no properties since Flex would have no visibility to the private members. I usually just let it slide, and create a Java good form wrapper object if I must for accessing on the server side. Doug --- In flexcoders@yahoogroups.com, ytseshred ytseshred@ wrote: That was a typo on my Part. They are being set using methods: TestVO vo = new TestVO(); vo.setID(rs.getInt(id)); vo.setData(rs.getString(data)); The problem has been solved by casting the result to ArrayCollection using the as keyword. I'm not sure what was causing my first problem, but I originally had my VO's defined with constructors, so I could create the VO like: TestVO vo = new TestVO(rs.getInt(id), rs.getString(data)); But Flex gave a runtime error when it was constructing the array collection saying something like TestVO init expected 2 arguments and got 0.
[flexcoders] Re: Trouble Converting java List to ArrayCollection
--- In flexcoders@yahoogroups.com, Doug Lowder [EMAIL PROTECTED] wrote:
Nope, I didn't misinterpret. I know TestVO is a Java class
(probably with a Flex counterpart class), and the way the Java class
is coded can definitely have an effect when it is accessed from
Flex. It isn't a case of correctness, but a case of what Flex
expects from Java classes. You can test this all out yourself by
implementing multiple constructors and/or declaring the properties
as private in your Java class.
Ok, I hate that I keep dragging this out but I also don't like when
people promote bad coding conventions. Here is a simple example java
bean, taken from Adobe.
package flex.testdrive.store;
public class Product {
private int productId;
private String name;
private String description;
private String image;
private String category;
private double price;
private int qtyInStock;
public Product() {
}
public Product(int productId, String name, String description,
String image, String category, double price, int qtyInStock) {
this.productId = productId;
this.name = name;
this.description = description;
this.image = image;
this.category = category;
this.price = price;
this.qtyInStock = qtyInStock;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public int getProductId() {
return productId;
}
public void setProductId(int productId) {
this.productId = productId;
}
public int getQtyInStock() {
return qtyInStock;
}
public void setQtyInStock(int qtyInStock) {
this.qtyInStock = qtyInStock;
}
}
You see all of the properties are private with public getters and
setters. When the Flex Data Services transfers the object to the
Flash Player it has all of the expected properties. This is proper,
correct and safe coding. Adobe even recommends this kind of coding
in ActionScript, which is why you use the set and get methods.
Paul
[flexcoders] Re: Trouble Converting java List to ArrayCollection
The multiple public constructors in the example is part of what I was
talking about. I wasn't aware Flex would play nice with private
properties, however. Perhaps I had that in my mind from classes that
didn't implement getters/setters, or maybe it's an improvement over
the Flex 1.5 days. In any case, thanks for the tip Paul.
--- In flexcoders@yahoogroups.com, lepusmars [EMAIL PROTECTED] wrote:
--- In flexcoders@yahoogroups.com, Doug Lowder douglowder@ wrote:
Nope, I didn't misinterpret. I know TestVO is a Java class
(probably with a Flex counterpart class), and the way the Java class
is coded can definitely have an effect when it is accessed from
Flex. It isn't a case of correctness, but a case of what Flex
expects from Java classes. You can test this all out yourself by
implementing multiple constructors and/or declaring the properties
as private in your Java class.
Ok, I hate that I keep dragging this out but I also don't like when
people promote bad coding conventions. Here is a simple example java
bean, taken from Adobe.
package flex.testdrive.store;
public class Product {
private int productId;
private String name;
private String description;
private String image;
private String category;
private double price;
private int qtyInStock;
public Product() {
}
public Product(int productId, String name, String description,
String image, String category, double price, int qtyInStock) {
this.productId = productId;
this.name = name;
this.description = description;
this.image = image;
this.category = category;
this.price = price;
this.qtyInStock = qtyInStock;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public int getProductId() {
return productId;
}
public void setProductId(int productId) {
this.productId = productId;
}
public int getQtyInStock() {
return qtyInStock;
}
public void setQtyInStock(int qtyInStock) {
this.qtyInStock = qtyInStock;
}
}
You see all of the properties are private with public getters and
setters. When the Flex Data Services transfers the object to the
Flash Player it has all of the expected properties. This is proper,
correct and safe coding. Adobe even recommends this kind of coding
in ActionScript, which is why you use the set and get methods.
Paul
