JExternal dv6.0E

Introduction

JExternal is a 4D plug-in to execute Java methods from within 4D. JExternal enables you to use many useful Java libraries in 4D. JExternal looks for Java files in "JavaClasses" folder and allows Java methods in those files to be used as if they were 4D plug-in methods. Besides JExternal allows the Java methods to callback 4D methods. Create a "JavaClasses" folder and put Java files whose extensions are ".jar" into it. Java methods in the Jar files can be executed from within 4D. Java methods called from within 4D are executed in a thread corresponding to a 4D process. If Java methods are called from two processes at the same time, they are executed in parallel. JExternal requires JWorld which is another plug-in to launch a Java virtual machine for JExternal. The JavaClasses folder may be located in the following folders: (1) The Contens folder of JExternal_xxx.bundle (2) The parent folder of the structure file (3) The parent folder of the application file (4th Dimension or 4DServer) (4) 4D folder The JavaClasses folder is searched in above order. Jar files in the JavaClasses folder found first are added to the classpath in Java. If JExternal is used with 4D Server, the JavaClasses folder in the Contents folder of JExternal_xxx.bundle is automatically downloaded to the clients.

System Requirements

JExternal works with 4th Dimension / 4D Server v 6.0 or later in Mac OS and Windows. On Intel-based Macs, JExternal doesn't work with 4D v2004 or earlier, because it cannot run on Rosetta. The current version (JExternal 6.0.0) requires 4D v11 or later, and Java 5 (JRE/JDK 1.5) or later on both platforms.

JEX Call class method ( ClassName; MethodName; Params ) --> Status [ C_LONGINT ]

Parameter	Type	Description
ClassName	C_TEXT	Java class name
MethodName	C_TEXT	Java method name
Params	ARRAY POINTER	Pointer array whose elements point to parameters to be passed to a Java method

JEX Call class method calls a Java class (static) method, whose class name is specified in ClassName and whose method name is specified in MethodName. In Params, specify a pointer array whose elements point to parameters to be passed to the Java method. The results of the Java method are returned through Params. After the Java method is executed, the size of Params may be changed and its elements will point to the results returned by the Java method. This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number. Refer to Type Conversion between 4D and Java and JEX Call object method.

Example Code

`Script to call class method "TestMethod1" in "TestClass1"
`
C_TEXT(vName)
C_BOOLEAN(vSex)
C_LONGINT(vAge)
C_LONGINT($Err)
`
vName:="Bill"
vSex:=True  `Male
ARRAY POINTER($Parameter;2)
$Parameter{1}:=->vName     `1st parameter
$Parameter{2}:=->vSex      `2nd parameter
$Err:=JEX Call class method("TestClass1";"TestMethod1";$Parameter)
If($Err=0)
    If(Size of array($Parameter) = 1)
        If(Type($Parameter{1}->) = Is LongInt)
            vAge:=$Parameter{1}->               `receive a result
        Else
            ALERT("Error:JEX Call class method")
        End if
    Else
        ALERT("Error:JEX Call class method")
    End if
Else
    ALERT("Error:JEX Call class method")
End if 

`Script to call class method "TestMethod2" in "TestClass1"
`
C_TEXT(vName)
C_BOOLEAN(vSex)
C_LONGINT($Err)
`
vName:="Bill Clinton"
vSex:=True  `Male
ARRAY TEXT(aHisCars;2)
aHisCars{1}:="Lincoln"
aHisCars{2}:="Porsche"
ARRAY POINTER($Parameter;3)
$Parameter{1}:=->vName      `1st parameter
$Parameter{2}:=->vSex       `2nd parameter
$Parameter{3}:=->aHisCars   `3rd parameter
$Err:=JEX Call class method("TestClass1";"TestMethod2";$Parameter)
If($Err=0)
  If(Size of array($Parameter)=1)
    If(Type($Parameter{1}->)=Text array)
      ARRAY TEXT(aHisChildren;0)
      COPY ARRAY($Parameter{1}->;aHisChildren)      `receive a result (array)
    Else
      ALERT("Error:JEX Call class method")
    End if
  Else
    ALERT("Error:JEX Call class method")
  End if
Else
  ALERT("Error:JEX Call class method")
End if 

`Script to call class method "TestMethod3" in "TestClass1"
`
C_TEXT(vName)
C_BOOLEAN(vSex)
C_LONGINT(vAge)
C_LONGINT($Err)
`
vName:="Bill Clinton"
vSex:=True  `Male
ARRAY TEXT(aHisCars;2)
aHisCars{1}:="Lincoln"
aHisCars{2}:="Porsche"
ARRAY POINTER($Parameter;3)
$Parameter{1}:=->vName      `1st parameter
$Parameter{2}:=->vSex       `2nd parameter
$Parameter{3}:=->aHisCars   `3rd parameter
$Err:=JEX Call class method("TestClass1";"TestMethod3";$Parameter)
If($Err=0)
  If(Size of array($Parameter)=2)
    If(Type($Parameter{1}->)=Is LongInt) & (Type($Parameter{2}->)=Text array)
      vAge:=$Parameter{1}->                       `receive the 1st result
      ARRAY TEXT(aHisChildren;0)
      COPY ARRAY($Parameter{2}->;aHisChildren)    `receive the 2nd result (array)
    Else
      ALERT("Error:JEX Call class method")
    End if
  Else
    ALERT("Error:JEX Call class method")
  End if
Else
  ALERT("Error:JEX Call class method")
End if 

//Java Class

import java.lang.*;
import com.ronri_kobo.*;
import com.ronri_kobo.JExternal.*;

public class TestClass1
{
   public static int TestMethod1( String name, boolean sex )
   {
      ..........
      ..........
      int age = 52;
      return age;
   }
   public static String[] TestMethod2( String name, boolean sex, String[] hisCars )
   {
      ..........
      ..........

      String[] hisChildren = new String[3];
      hisChildren[0] = "John";
      hisChildren[1] = "Mary";
      hisChildren[2] = "Mike";

      return hisChildren;
   }

   public static Object[] TestMethod3(String name, boolean sex, String[] hisCars)
   {
      ..........
      ..........

      int age = 52;
      String[] hisChildren = new String[3];
      hisChildren[0] = "John";
      hisChildren[1] = "Mary";
      hisChildren[2] = "Mike";

      Object[] retArray = new Object[2];
      retArray[0] = (Object)( new Integer( age ) );
      retArray[1] = (Object)hisChildren;

      return retArray;
   }
}

JEX Call object method ( ObjectID; MethodName; Params ) --> Status [ C_LONGINT ]

Parameter	Type	Description
ObjectID	C_LONGINT	ID number by which a Java object is identified
MethodName	C_TEXT	Java method name
Params	ARRAY POINTER	Pointer array whose elements point to parameters to be passed to a Java method

JEX Call object method calls a Java object (instance) method, whose object ID is specified in ObjectID and whose method name is specified in MethodName. An object ID is a positive number that identifies a Java object. Refer to Example Code below to know how to get an object ID. In Params, specify a pointer array whose elements point to parameters to be passed to the Java method. The results of the Java method are returned through Params. After the Java method is executed, the size of Params may be changed and its elements will point to the results returned by the Java method. This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number. Refer to Type Conversion between 4D and Java and JEX Call class method.

Example Code

Script to call object method "TestMethod" in "TestClass2"
`
C_TEXT(vName)
C_BOOLEAN(vSex)
C_LONGINT(vAge)
C_LONGINT($TargetObjetID)
C_LONGINT($Err)
`
ARRAY POINTER($Parameter;0)        `No parameter
$Err:=JEX Call class method("TestClass2";"createMyself";$Parameter)
If($Err=0)
  If(Size of array($Parameter)=1)
    If(Type($Parameter{1}->)=Is LongInt)
      $TargetObjetID:=$Parameter{1}->  `receive a result
`
      vName:="Bill"
      vSex:=True  `Male
      ARRAY POINTER($Parameter;2)
      $Parameter{1}:=->vName          `1st parameter
      $Parameter{2}:=->vSex           `2nd parameter
      $Err:=JEX Call object method($TargetObjetID;"TestMethod";$Parameter)
      If($Err=0)
        If(Size of array($Parameter)=1)
          If(Type($Parameter{1}->)=Is LongInt)
            vAge:=$Parameter{1}->                 `receive a result
            $Err:=JEX Free object($TargetObjetID) `Dispose the Java object
            If($Err # 0)
              ALERT("Error:JEX Free object")
            End if
          Else
            ALERT("Error:JEX Call object method")
          End if
        Else
          ALERT("Error:JEX Call object method")
        End if
      Else
        ALERT("Error:JEX Call object method")
      End if
    Else
      ALERT("Error:JEX Call class method")
    End if
  Else
    ALERT("Error:JEX Call class method")
  End if
Else
  ALERT("Error:JEX Call class method")
End if 

//Java Class

import java.lang.*;
import com.ronri_kobo.*;
import com.ronri_kobo.JExternal.*;

public class TestClass2
{
   public TestClass2()
   {
      super();
   }

   public static int createMyself()
   {
      TestClass2 obj      = new TestClass2();
      int        objectID = DBWorld.createObjectID( obj );
      return     objectID;
   }

   public int TestMethod( String name, boolean sex )
   {
      ..........
      ..........

      int age = 52;
      return age;
   }
}

JEX Free object ( ObjectID ) --> Status [ C_LONGINT ]

Parameter	Type	Description
ObjectID	C_LONGINT	ID number by which a Java object is identified

JEX Free object releases the memory for the Java object identified by ObjectID. After this method is executed, don't use this ID number again, because the Java object might be deallocated by the garbage collection. This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number. Refer to Example Code for JEX Call object method.

JEX Set environment ( JVM_ID; ProductType ) --> Status [ C_LONGINT ]

Parameter	Type	Description
JVM_ID	C_LONGINT	ID for a Java virtual machine JWD create java world returns
ProductType	C_TEXT	"PRODUCT" or "TRIAL"

JEX Set environment setups the environment for JExternal. This method has to be executed before executing any other JExternal plug-in methods. This method is usually called at "On Startup". In JVM_ID, specify an ID number for a Java virtual machine which JWD create java world returns. In ProductType, Specify "PRODUCT" normally. If you want to use your application with JExternal in trial mode, specify "TRIAL". This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number.

Example Code

`Setup the environment for JExternal in "On Startup" method
`
C_LONGINT($JVM_ID)
C_LONGINT($Err)
` 
$JVM_ID:=JWD Create java world("BUIT-IN")
If($JVM_ID>0)
  $Err:=JEX Set environment ($JVM_ID;"PRODUCT")
  If($Err # 0)
    ALERT("Error:JEX Set environment")
  End if
Else
  ALERT("Error:JWD Create java world")
End if 

JWorld

JWorld is a plug-in for 4D to launch a Java virtual machine (JVM). JExternal itself doesn't launch it. JWorld has following plug-in methods: JWD Create java world JWD Close java world JWD Convert line separator JWD Set JVM options In Mac OS, Apple's built-in JVM is launched by JWorld. In Windows, if JWorld 6.0.0 or later is used, JWorld's built-in JVM is launched. If JWorld 5.x.x or earlier version is used in Windows, you have to install a JVM which is downloadable at the following URL: http://java.sun.com/javase/downloads/

JWD Create java world ( JVM_Path )--> JVM_ID [ C_LONGINT ]

Parameter	Type	Description
JVM_Path	C_TEXT	"BUILT-IN", "" (blank) or a path to jvm.dll (wondows)

JWD Create java world launches a Java virtual machine (JVM) and returns its ID number. In Mac OS, JVM_Path is always ignored and Apple's built-in JVM is launched. In Windows, specify "BUILT-IN", "" (blank) or a path to jvm.dll in JVM_Path. If "BUILT-IN" is specified in JVM_Path using JWorld 6.0.0 or later in Windows, JWorld's built-in JVM is launched. This built-in JVM is "JRE version 6 Update 18" , which is located "Plugins/JWorld_xxx.bundle/Contents/Windows/JRE". If the built-in JVM is not found in the directory, it is considered that "" (blank) is specified in JVM_Path. If JWorld 5.x.x or earlier is used, it is also considered that "" (blank) is specified. If "" (blank) is specified in JVM_Path in Windows, your installed JVM is launched referring to the Registry. If a path to jvm.dll is specified in JVM_Path in Windows, the JVM identified by the path is launched. Example of the path to jvm.dll in Windows JRE 1.6.0_02 "C:\Program Files\Java\jre1.6.0_02\bin\client\jvm.dll" JDK 1.6.0_02 "C:\Program Files\Java\jdk1.6.0_02\jre\bin\client\jvm.dll" This plug-in method should be called in "On Startup" or in a process started in "On Server Startup". This method returns a positive number (JVM_ID), if there is no error. If any error occurred, it returns a negative number. Refer to Error Number.

Example Code

C_LONGINT($JVM_ID)
C_LONGINT($Err)
`
ARRAY TEXT($Options;2)
$Options{1}:="-Xms128M"
$Options{2}:="-Xmx128M"
$Err:=JWD Set JVM options( $Options )
If($Err=0)
  $JVM_ID:=JWD Create java world("BUILT-IN")
  If($JVM_ID>0)
    $Err:=JEX Set environment($JVM_ID;"PRODUCT")
    If($Err # 0)
      ALERT("Error:JEX Set environment")
    End if
  Else
    ALERT("Error:JWD Create java world")
  End if 
Else
  ALERT("Error:JWD Set JVM options")
End if

JWD Close java world --> Status [ C_LONGINT ]

Parameter	Type	Description
(None)

JWD Close java world terminates JWorld. Call this method in "On Exit" or "On Server Shutdown". This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number.

Example Code

C_LONGINT($Err)
$Err:=JWD Close java world

JWD Convert line separator ( Switch ) --> Status [ C_LONGINT ]

Parameter	Type	Description
Switch	C_BOOLEAN	If Switch is True, Line separators are converted (CR <-> LF). If Switch is False, they are not converted.

If "True" is passed to JWD Convert line separator, all CRs (carriage return) are automatically converted to LFs (line feed) when 4D strings are sent to Java. And all LFs are automatically converted to CRs when Java strings are sent to 4D. If "False" is passed to this method, any line separators are not converted. This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number.

Example Code

C_LONGINT($Err)
$Err:=JWD Convert line separator( True )

JWD Set JVM options ( Options ) --> Status [ C_LONGINT ]

Parameter	Type	Description
Options	ARRAY TEXT	Text array whose elements are JVM options.

JWD Set JVM options sets Java virtual machine options. Pass a text array whose elements are the options. Call this method before JWD Create java world is executed. Refer to the following web page about JVM options: http://blogs.sun.com/watt/resource/jvm-options-list.html If an option "-Djworld.stdout.redirect=true" is set, stdout and stderr can be redirected to a file whose name is "jworldout.txt" which is located in the same level as the structure file. This method returns 0, if there is no error. If any error occurred, it returns a negative number. Refer to Error Number.

Example Code

C_LONGINT($Err)
C_LONGINT($JVM_ID)
`
ARRAY TEXT($Options;3)
$Options{1}:="-Xms128M"
$Options{2}:="-Xmx128M"
$Options{3}:="-Djworld.stdout.redirect=true"
`
$Err:=JWD Set JVM options( $Options )
If ($Err=0)
    $JVM_ID:=JWD Create java world( "BUILT-IN" )
    ...
End if

Java Class Library

We provide Java developers with class libraries JExternal_xxx.jar and JWorld_xxx.jar to develop Java programs used in 4D. The class libraries is located in Plugins/JWorld_xxx.bundle/Contents/RonriKobo folder.

com.ronri_kobo.JExternal.DBWorld	(JExternal_xxx.jar)
com.ronri_kobo.Time	(JWorld_xxx.jar)
com.ronri_kobo.Date	(JWorld_xxx.jar)
com.ronri_kobo.Picture	(JWorld_xxx.jar)
com.ronri_kobo.JExternal.InvalidProcessNoException	(JExternal_xxx.jar)
com.ronri_kobo.JExternal.InvalidMethodNameException	(JExternal_xxx.jar)
com.ronri_kobo.JExternal.InvalidParametersException	(JExternal_xxx.jar)

Class com.ronri_kobo.JExternal.DBWorld

java.lang.Object
   |
   +----com.ronri_kobo.JExternal.DBWorld

public class DBWorld extends java.lang.Object

This class is a stub of 4D. This class has 1 constructor and 2 class methods 1 instance method as follows:

DBWorld

public DBWorld(int processNo) throws com.ronri_kobo.JExternal.InvalidProcessNoException

This constructor requires a 4D process number specified in processNo. In the process, callback methods will be executed. Refor to call4Dmethod below.

createObjectID

public static synchronized int createObjectID(java.lang.Object obj)

This method returns the ID number of a object specified in obj, by which the object can be identified in 4D. This method prevents the garbage collection from deallocating the object. The ID number is used in JEX Call object method and JEX Free object.

alert

public static synchronized void alert(java.lang.String message)

This method displays a alert dialog box with message. This method corresponds with 4D command "ALERT".

call4DMethod

public java.lang.Object call4DMethod(java.lang.String methodName,
                                     java.lang.Object[] parameter)
                         throws com.ronri_kobo.JExternal.InvalidMethodNameException,
                                com.ronri_kobo.JExternal.InvalidParametersException

This method callbacks a 4D method, whose method name is specified in methodName. The 4D method is executed in a process whose number was passed to the constructor DBWorld. When the 4D method is called, JEX Call class method or JEX Call object method must be executed in the process. These plug-in methods can yield their process time to the callback method. In parameter, specify an array of the Object class whose elements are parameters to be passed the 4D method. To pass primitive types (int, double...), the wrapper objects must be created for them. This method always returns an object of the Object class, which corresponds with $0 in the 4D method. The object will be unwrapped or cast to use in your program. If the 4D method returns a pointer to a ARRAY POINTER, this method returns an array of the Object class whose elements correspond with the elements of the ARRAY POINTER. The elements of the array will be unwrapped or cast to use in your program. Refer to Type Mapping and demos for JExternal.

Example Code

import java.lang.*;
import com.ronri_kobo.*;
import com.ronri_kobo.JExternal.*;

public class TestClass
{
  static DBWorld dbWorld;

  /**************************/
  // Constructor
  /**************************/
  public TestClass()
  {
     super();
  }

  /**************************/
  // createMyself  -- will be called by JEX Call class method
  /**************************/
  public static int createMyself()
  {
    int        objectID;
    TestClass  obj = new TestClass();
    objectID = DBWorld.createObjectID( obj );
    return     objectID;
   }

  /**************************/
  // createDBWorld  -- will be called by JEX Call class method
  /**************************/
  public static void createDBWorld(int processNo)
  {
    try{
      dbWorld = new DBWorld( processNo );
    }
    catch( InvalidProcessNoException e ){
      DBWorld.alert( "An InvalidProcessNoException occurred" );
    }
  }

  /**************************/
  // callback
  /**************************/
  public Object callback( String callbackMethodName, Object params[] )
  {
    Object result = null;
    try{
      result = dbWorld.call4DMethod( callbackMethodName, params );
    }
    catch( InvalidMethodNameException e ){
      DBWorld.alert( "An InvalidMethodNameException occurred." );
    }
    catch( InvalidParametersException e ){
      DBWorld.alert( "An InvalidParametersException occurred." );
    }
    return result;
  }

  /**************************/
  // testMethod
  /**************************/
  public void testMethod()
  {
    boolean  sex  = false;    //female
    String   name = "Monica";
    Object[] params = new Object[ 2 ];
    params[ 0 ]     = new Boolean( sex );   // 1st Parameter
    params[ 1 ]     = name;                 // 2nd Parameter

    Object resultObj = callback( "QueryAge", params );
    if( resultObj != null )
       int herAge = ( (Integer)resultObj ).intValue();
    ..........
    ..........

  }
}

`4D Method "QueryAge" --- callback method
C_BOOLEAN($1) `Sex
C_TEXT($2)    `Name
`
QUERY([Personnel];[Personnel]Sex=$1;*)
QUERY([Personnel]; & ;[Personnel]Name=$2)
`
C_LONGINT($0) `Age
$0:=[Personnel]Age

Class com.ronri_kobo.Time

java.lang.Object
   |
   +----com.ronri_kobo.Time

public class Time extends java.lang.Object implements java.io.Serializable

This class is in JWorld_xxx.jar in RonriKobo folder and corresponds with C_TIME in 4D.

Time

public Time(int hour, int min, int sec)

This method creates an object of the Time class and initializes its hour, minute and second with specified values.

getHours

public int getHours()

This method returns the hour of the Time object.

getMinutes

public int getMinutes()

This method returns the minute of the Time object.

getSeconds

public int getSeconds()

This method returns the second of the Time object.

setHours

public void setHours(int hour)

This method replaces the current hour of the Time object with a specified value.

setMinutes

public void setMinutes(int min)

This method replaces the current minute of the Time object with a specified value.

setSeconds

public void setSeconds(int sec)

This method replaces the current second of the Time object with a specified value.

Class com.ronri_kobo.Date

java.lang.Object
   |
   +----com.ronri_kobo.Date

public class Date extends java.lang.Object implements java.io.Serializable

This class is in JWorld_xxx.jar in RonriKobo folder and corresponds with C_DATE in 4D.

Date

public Date(int year, int month, int date)

This method creates an object of the Date class and initializes its year, month and date with specified values.

getYear

public int getYear()

This method returns the year (0-32767) of the Date object.

getMonth

public int getMonth()

This method returns the month (1-12) of the Date object.

getDate

public int getDate()

This method returns the day (1-31) of the Date object.

setYear

public void setYear(int year)

This method replaces the current year of the Date object with a specified value (0-32767).

setMonth

public void setMonth(int month)

This method replaces the current month of a Date object with a specified value (1-12).

setDate

public void setDate(int date)

This method replaces the current date of the Date object with a specified value (1-31).

Class com.ronri_kobo.Picture

java.lang.Object
   |
   +----com.ronri_kobo.Picture

public class Picture extends java.lang.Object implements java.io.Serializable

This class is in JWorld_xxx.jar in RonriKobo folder. and corresponds with C_PICTURE in 4D.

Picture

public Picture(byte picture[])

This method creates an object of the Picture class and initializes it with the specified byte array.

getBytes

public byte[] getBytes()

This method converts the Picture object into a byte array and returns it.

setBytes

public void setBytes(byte picture[])

This method converts the specified byte array into a Picture object and replaces the current Picture object with it.

Class com.ronri_kobo.JExternal.InvalidProcessNoException

java.lang.Object
   |
   +----java.lang.Throwable
           |
           +----java.lang.Exception
                   |
                   +----com.ronri_kobo.JExternal.InvalidProcessNoException

public class InvalidProcessNoException extends java.lang.Exception

This exception occurs when an invalid process number of 4D is passed to DBWorld.

InvalidProcessNoException

 public InvalidProcessNoException()

Class com.ronri_kobo.JExternal.InvalidMethodNameException

java.lang.Object
   |
   +----java.lang.Throwable
           |
           +----java.lang.Exception
                   |
                   +----com.ronri_kobo.JExternal.InvalidMethodNameException

public class InvalidMethodNameException extends java.lang.Exception

This exception occurs when an invalid method name is passed to call4DMethod.

InvalidMethodNameException

 public InvalidMethodNameException()

Class com.ronri_kobo.JExternal.InvalidParametersException

java.lang.Object
   |
   +----java.lang.Throwable
           |
           +----java.lang.Exception
                   |
                   +----com.ronri_kobo.JExternal.InvalidParametersException

public class InvalidParametersException extends java.lang.Exception

This exception occurs when invalid parameters are passed to call4DMethod.

InvalidParametersException

public InvalidParametersException()

When passing parameters to a Java method or receiving results from a Java method, their data types are converted as follows:

4D	<->	Java
C_BOOLEAN	<->	boolean
C_INTEGER	->	int
C_LONGINT	<->	int
C_REAL	<->	double
C_TIME	<->	com.ronri_kobo.Time
C_DATE	<->	com.ronri_kobo.Date
C_TEXT	<->	java.lang.String
C_PICTURE	<->	com.ronri_kobo.Picture
C_BLOB	<->	byte[]
ARRAY BOOLEAN	<->	boolean[]
ARRAY INTEGER	<->	short[]
ARRAY LONGINT	<->	int[]
ARRAY REAL	<->	double[]
ARRAY DATE	<->	com.ronri_kobo.Date[]
ARRAY TEXT	<->	java.lang.String[]
ARRAY PICTURE	<->	com.ronri_kobo.Picture[]

Error Number

-15901	Java session could not be opened
-15902	Old version of 4D
-15903	68K Macintosh is used
-15904	Old version of Mac OS
-15905	Old version of MRJ
-15906	JWorld_xxx.jar was not found
-15920	Java session was not yet opened
-15922	Basic Java classes for JWorld were not found
-15923	Basic Java methods for JWorld were not found
-15924	libJWorld.jnilib was not found
-15925	java.security was not found
-15926	An error occurred when the classpath was set
-15927	Not enough memory for the classpath
-15928	An error occurred when the Java VM thread was created
-15929	Invalid Java VM DLL
-15930	jvm.dll was not found
-15931	Old version of Java VM (In Windows J2SE is required as a Java VM)
-17002	Invalid class name
-17003	Invalid method name
-17005	A pointer array was not specified
-17301	The Java method could not be executed
-17302	The Java object was not found
-18000	Trial is over
-18007	JExternal_xxx.jar was not found
-18010	Basic Java classes for JExternal were not found
-18011	Basic Java methods for JExternal were not found
-18012	Invalid JVM ID
-18021	The plug-in method tried to be executed before executing JEX Set environment
-18022	Invalid parameters
-18023	Not enough memory-1
-18024	Not enough memory-2
-18025	Not enough memory-3
-18029	Invalid return type(s)

Limitations

1	A Java method cannot return over 99 results to 4D.
2	A Java method cannot pass over 99 parameters to a callback method.
3	Any two-dimensional array cannot be passed and returned between 4D and Java.
4	A Java method cannot be called in a callback method.
5	Any user interface components cannot be used in a Java method.
6	The plug-in names of JExternal_xxx.bundle and JWorld_xxx.bundle cannot be changed.

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