HostAccess (GraalVM SDK Java API Reference)

java.lang.Object
- org.graalvm.polyglot.HostAccess

```
public final class HostAccess
extends Object
```
Represents the host access policy of a polyglot context. The host access policy specifies which methods and fields are accessible to the guest application, whenever Java host objects are accessed.
There are three predefined instances of host access policies:
- HostAccess.EXPLICIT - Java host methods or fields, must be public and be annotated with @Export to make them accessible to the guest language.
- HostAccess.SCOPED - Java host methods or fields, must be public and be annotated with @Export to make them accessible to the guest language. Guest-to-host callback parameter validity is scoped to the duration of the callback by default.
- HostAccess.NONE - Does not allow any access to methods or fields of host objects. Java host objects may still be passed into a context, but they cannot be accessed.
- HostAccess.ALL - Does allow full unrestricted access to public methods or fields of host objects. Note that this policy allows unrestricted access to reflection. It is highly discouraged from using this policy in environments where the guest application is not fully trusted.
- HostAccess.CONSTRAINED host access policy suitable for a context with CONSTRAINED sandbox policy.
- HostAccess.ISOLATED host access policy suitable for a context with ISOLATED sandbox policy.
- HostAccess.UNTRUSTED host access policy suitable for a context with UNTRUSTED sandbox policy.
Custom host access policies can be created using HostAccess.newBuilder(). The builder allows to specify a custom export annotation and allowed and denied methods or fields.
Since:

19.0

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`class`	`HostAccess.Builder` Builder to create a custom `host access policy`.
`static interface`	`HostAccess.DisableMethodScoping` If `HostAccess.SCOPED` is used, placing this annotation on an exported host function excludes it from parameter scoping, i.e.
`static interface`	`HostAccess.Export` Annotation used by the predefined `HostAccess.EXPLICIT` access policy to mark public constructors, methods and fields in public classes that should be accessible by the guest application.
`static interface`	`HostAccess.Implementable` Allows guest language to implement a Java type.
`static class`	`HostAccess.MutableTargetMapping` List of default host object mappings of mutable target types available in `Value.as(Class)`.
`static class`	`HostAccess.TargetMappingPrecedence` Represents the precedence of a target type mapping.

Field Summary

Fields
Modifier and Type	Field and Description
`static HostAccess`	`ALL` Predefined host access policy that allows full unrestricted access to public methods or fields of public host classes.
`static HostAccess`	`CONSTRAINED` Predefined host access policy used by Context with a `SandboxPolicy.CONSTRAINED` sandbox policy when the host access policy is not explicitly specified by the embedder.
`static HostAccess`	`EXPLICIT` Predefined host access policy that allows access to public host methods or fields that were annotated with @Export and were declared in public class.
`static HostAccess`	`ISOLATED` Predefined host access policy used by Context with an `SandboxPolicy.ISOLATED` sandbox policy when the host access policy is not explicitly specified by the embedder.
`static HostAccess`	`NONE` Predefined host access policy that disallows any access to public host methods or fields.
`static HostAccess`	`SCOPED` Predefined host access policy that is the same as EXPLICIT and enables method scoping of callback parameter values on top.
`static HostAccess`	`UNTRUSTED` Predefined host access policy used by Context with an `SandboxPolicy.UNTRUSTED` sandbox policy when the host access policy is not explicitly specified by the embedder.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`equals(Object obj)`
`int`	`hashCode()`
`static HostAccess.Builder`	`newBuilder()` Creates a new builder that allows to create a custom host access policy.
`static HostAccess.Builder`	`newBuilder(HostAccess conf)` Creates a new builder that allows to create a custom host access policy based of a preset configuration.
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - EXPLICIT
```
public static final HostAccess EXPLICIT
```
    Predefined host access policy that allows access to public host methods or fields that were annotated with @Export and were declared in public class. This is the default configuration if Context.Builder.allowAllAccess(boolean) is false.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder().allowAccessAnnotatedBy(HostAccess.Export.class).
                allowImplementationsAnnotatedBy(HostAccess.Implementable.class).
                allowImplementationsAnnotatedBy(FunctionalInterface.class).
                .build();
 
 
```
    Since:
    
    19.0
  - SCOPED
```
public static final HostAccess SCOPED
```
    Predefined host access policy that is the same as EXPLICIT and enables method scoping of callback parameter values on top. Methods that are annotated with HostAccess.DisableMethodScoping are exempt from scoping.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder().allowAccessAnnotatedBy(HostAccess.Export.class).
                 allowImplementationsAnnotatedBy(HostAccess.Implementable.class).
                 allowImplementationsAnnotatedBy(FunctionalInterface.class).
                 methodScoping(true).
                 disableMethodScopingAnnotatedBy(HostAccess.DisableMethodScoping.class)
                 .build();
 
 
```
    Since:
    
    21.3
  - ALL
```
public static final HostAccess ALL
```
    Predefined host access policy that allows full unrestricted access to public methods or fields of public host classes. Note that this policy allows unrestricted access to reflection. It is highly discouraged from using this policy in environments where the guest application is not fully trusted. This is the default configuration if Context.Builder.allowAllAccess(boolean) is true.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder()
           allowPublicAccess(true).
           allowAllImplementations(true).
           allowAllClassImplementations(true).
           allowArrayAccess(true).
           allowListAccess(true).
           allowBufferAccess(true).
           allowIterableAccess(true).
           allowIteratorAccess(true).
           allowMapAccess(true).
           allowAccessInheritance(true).
           .build();
 
 
```
    Since:
    
    19.0
  - NONE
```
public static final HostAccess NONE
```
    Predefined host access policy that disallows any access to public host methods or fields.
    Equivalent of using the following builder configuration:
```
 HostAccess.newBuilder().build();
 
```
    Since:
    
    19.0
  - CONSTRAINED
```
public static final HostAccess CONSTRAINED
```
    Predefined host access policy used by Context with a SandboxPolicy.CONSTRAINED sandbox policy when the host access policy is not explicitly specified by the embedder.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder().
           allowAccessAnnotatedBy(Export.class).
           allowImplementationsAnnotatedBy(Implementable.class).
           allowMutableTargetMappings().build();
 
 
```
    Since:
    
    23.0
  - ISOLATED
```
public static final HostAccess ISOLATED
```
    Predefined host access policy used by Context with an SandboxPolicy.ISOLATED sandbox policy when the host access policy is not explicitly specified by the embedder.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder(CONSTRAINED).
           methodScoping(true).build();
 
 
```
    Since:
    
    23.0
  - UNTRUSTED
```
public static final HostAccess UNTRUSTED
```
    Predefined host access policy used by Context with an SandboxPolicy.UNTRUSTED sandbox policy when the host access policy is not explicitly specified by the embedder.
    Equivalent of using the following builder configuration:
```
 
 HostAccess.newBuilder().
           allowAccessAnnotatedBy(Export.class).
           allowMutableTargetMappings().
           methodScoping(true).build();
 
 
```
    Since:
    
    23.0
- Method Detail
  - equals
```
public boolean equals(Object obj)
```
    Overrides:
    
    equals in class Object
    
    Since:
    
    20.3
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
    
    Since:
    
    20.3
  - newBuilder
```
public static HostAccess.Builder newBuilder()
```
    Creates a new builder that allows to create a custom host access policy. The builder configuration needs to be completed using the method.
    
    Since:
    
    19.0
  - newBuilder
```
public static HostAccess.Builder newBuilder(HostAccess conf)
```
    Creates a new builder that allows to create a custom host access policy based of a preset configuration. The preset configuration is copied and used as a template for the returned buidler. The builder configuration needs to be completed using the method.
    
    Since:
    
    19.0
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
    
    Since:
    
    19.0

Class HostAccess

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

EXPLICIT

SCOPED

ALL

NONE

CONSTRAINED

ISOLATED

UNTRUSTED

Method Detail

equals

hashCode

newBuilder

newBuilder

toString