Standard library

jballerina.java

Module jballerina.java

cast
createNull
fromString
getClass
isNull
toString

SpanImplStackFrameImpl

JObject

ArrayType
ConstructorData
FieldData
MethodData
ObjectData

Binding
Constructor
FieldGet
FieldSet
Method

Class
Identifier

JavaClassNotFoundError

ballerina/jballerina.java

0.0.0

Module overview

This module provides library operations required for Java interoperability in Ballerina. It includes a set of Ballerina annotations with which Java constructors, methods, and fields can provide implementations of Ballerina functions with external function bodies.

For information on the operations, which you can perform with the Java module, see the following learn page.

Functions

cast

Isolated Function
function cast(JObject value, typedesc<JObject> t) returns t|error

Performs a Java cast operation on a value. This casts a value describing a JObject to a type describing a JObject based on Java assignability, returns an error if the cast cannot be done.

Copy
FileInputStream|error obj = java:cast(inputStream);
Parameters
  • value JObject - A value describing a JObject which is to be casted
  • t typedesc<JObject> (default <>) - A type describing a JObject to which the value is to be casted
Return Type
  • t|error - A value belonging to parameter t or an error if this cast cannot be done

createNull

Isolated Function
function createNull() returns handle

Returns a handle, which refers to Java null.

Copy
handle nullHandle = java:createNull();
Return Type
  • handle - The handle, which refers to Java null

fromString

Isolated Function
function fromString(string value) returns handle

Returns a handle, which refers to the Java string representation of the Ballerina string.

Copy
handle header = java:fromString("Content-Type");
Parameters
  • value string - The Ballerina string with which the handle is created
Return Type
  • handle - The handle, which refers to the Java String representation of the Ballerina string

getClass

Isolated Function
function getClass(string name) returns handle|error

Returns a handle, which refers to the Java Class object associated with the class or interface with the given string name.

Copy
handle|error intClass = java:getClass("int");

This function performs a Java class.forName(name) except for the following cases:

NameOutput
booleanJava Class instance representing the primitive type boolean
byteJava Class instance representing the primitive type byte
charJava Class instance representing the primitive type char
shortJava Class instance representing the primitive type short
intJava Class instance representing the primitive type int
longJava Class instance representing the primitive type long
floatJava Class instance representing the primitive type float
doubleJava Class instance representing the primitive type double
Parameters
  • name string - The name of the Java class
Return Type
  • handle|error - The Java Class object for the class with the given name

isNull

Isolated Function
function isNull(handle value) returns boolean

Returns true if this handle refers to Java null.

Copy
boolean status = java:isNull(value);
Parameters
  • value handle - The handle of which the referred value is to be tested with Java null
Return Type
  • boolean - true if this handle refers to Java null

toString

Isolated Function
function toString(handle value) returns string?

Returns a Ballerina string representation of the Java object referred by the handle. If the handle refers to Java null, then this function returns a nil value.

Copy
string? version = java:toString(versionProperty);
Parameters
  • value handle - The handle of which the referred value is to be converted to a Ballerina string
Return Type
  • string? - The Ballerina string representation of the Java object referred by the handle or else returns () if the handle refers to Java null

Classes

jballerina.java: SpanImpl

Read Only

Implementation for the regexp.Span.

substring

Isolated Function
function substring() returns string
Fields
  • startIndex int - Callable name
  • endIndex int - Module name

jballerina.java: StackFrameImpl

Read Only

Implementation for the runtime.StackFrame.

toString

Isolated Function
function toString() returns string

Returns a string representing for the StackFrame.

Return Type
  • string - A stack frame as string
Fields
  • callableName string - Callable name
  • moduleName string? - Module name
  • lineNumber int - Line number

Object types

jballerina.java: JObject

The Ballerina abstract object which is to be extended by Ballerina objects representing Ballerina bindings for Java classes.

Fields
  • jObj handle - The handle reference to the corresponding Java object.

Records

jballerina.java: ArrayType

Closed record

Represents a Java array type. It is used to specify the parameter types in the java:Constructor and java:Method annotations.

Fields
  • dimensions byte - Dimensions of the array type

jballerina.java: ConstructorData

Closed record

Describes a Java constructor. If the paramTypes field is not specified, then the parameter types are inferred from the corresponding Ballerina function.

Fields
  • paramTypes (Class|ArrayType)[]? - An optional field, which describes the parameter types of the constructor

jballerina.java: FieldData

Closed record

Describes a Java field.

Fields
  • name Identifier - An optional field, which describes the name of the Java field. If this field is not provided, then the name is inferred from the Ballerina function name

jballerina.java: MethodData

Closed record

Describes a Java method. If the paramTypes field is not specified, then the parameter types are inferred from the corresponding Ballerina function.

Fields
  • name Identifier? - An optional field, which describes the name of the Java method. If this field is not provided, then the name is inferred from the Ballerina function name
  • paramTypes (Class|ArrayType)[]? - An optional field, which describes the parameter types of the method

jballerina.java: ObjectData

Closed record

Describes a Java class that corresponds to a Ballerina object.

Fields

Annotations

jballerina.java: Binding

ObjectData class

Describes the Java class representing a Ballerina binding.

Copy
@java:Binding {
  'class: "java.io.File"
}

jballerina.java: Constructor

ConstructorData source external

Describes a Java constructor, which provides an implementation of a Ballerina function of which the body is marked as external. If the Ballerina function body is marked as external, it means that the implementation of the function is not provided in the Ballerina source module.

The following code snippet shows an example usage of this annotation. Here, the newJavaLinkedList Ballerina function's implementation is provided by the default constructor of the java.util.LinkedList class.

Copy
function newJavaLinkedList() returns handle = @java:Constructor {
     'class: "java.util.LinkedList"
} external;

jballerina.java: FieldGet

FieldData source external

Describes a Java Field access, which provides an implementation of a Ballerina function of which the body is marked as external.

Copy
function getError() returns handle = @java:FieldGet {
    name:"err",
    'class:"java/lang/System"
} external;

jballerina.java: FieldSet

FieldData source external

Describes a Java Field mutate, which provides an implementation of a Ballerina function of which the body is marked as external.

Copy
function setContractId(handle contractId) = @java:FieldSet {
  name:"contractId",
  'class:"org/lang/impl/JavaFieldAccessMutate"
} external;

jballerina.java: Method

MethodData source external

Describes a Java method, which provides an implementation of a Ballerina function of which the body is marked as external. If the Ballerina function body is marked as external, it means that the implementation of the function is not provided in the Ballerina source module.

The following code snippet shows an example usage of this annotation. Here, the getUUID Ballerina function's implementation is provided by the java.util.UUID.randomUUID static method.

Copy
function getUUID() returns handle = @java:Method {
    name: "randomUUID",
    'class: "java.util.UUID"
} external;

The name field is optional. If it is not provided, the name of the Java method is inferred from the Ballerina function.

Types

jballerina.java: Class

string

Represents a Java class name.

jballerina.java: Identifier

string

Represents a Java identifier.

Errors

jballerina.java: JavaClassNotFoundError

Distinct
map<readonly|xml|Cloneable[]|map<Cloneable>|table<map<ballerina/jballerina.java:0.0.0:Cloneable>>>

Represents a JavaError with the message and the cause.

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