# Class Validator

java.lang.Object
javax.xml.validation.Validator

public abstract class Validator extends Object
A processor that checks an XML document against `Schema`.

A validator object is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one `Validator` object is not used from more than one thread at any given time, and while the `validate` method is invoked, applications may not recursively call the `validate` method.

Since:
  1.5

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`Validator()`
Constructor for derived classes.

## Method Summary

Modifier and Type
Method
Description
`abstract ErrorHandler`
`getErrorHandler()`
Gets the current `ErrorHandler` set to this `Validator`.
`boolean`
`getFeature(String name)`
Look up the value of a feature flag.
`Object`
`getProperty(String name)`
Look up the value of a property.
`abstract LSResourceResolver`
`getResourceResolver()`
Gets the current `LSResourceResolver` set to this `Validator`.
`abstract void`
`reset()`
Reset this `Validator` to its original configuration.
`abstract void`
`setErrorHandler(ErrorHandler errorHandler)`
Sets the `ErrorHandler` to receive errors encountered during the `validate` method invocation.
`void`
`setFeature(String name, boolean value)`
Set the value of a feature flag.
`void`
`setProperty(String name, Object object)`
Set the value of a property.
`abstract void`
`setResourceResolver(LSResourceResolver resourceResolver)`
Sets the `LSResourceResolver` to customize resource resolution while in a validation episode.
`void`
`validate(Source source)`
Validates the specified input.
`abstract void`
`validate(Source source, Result result)`
Validates the specified input and send the augmented validation result to the specified output.

### Methods declared in class Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Constructor Details

### Validator

protected Validator()
Constructor for derived classes.

The constructor does nothing.

Derived classes must create `Validator` objects that have `null` `ErrorHandler` and `null` `LSResourceResolver`.

## Method Details

### reset

public abstract void reset()
Reset this `Validator` to its original configuration.

`Validator` is reset to the same state as when it was created with `Schema.newValidator()`. `reset()` is designed to allow the reuse of existing `Validator`s thus saving resources associated with the creation of new `Validator`s.

The reset `Validator` is not guaranteed to have the same `LSResourceResolver` or `ErrorHandler` `Object`s, e.g. `Object.equals(Object obj)`. It is guaranteed to have a functionally equal `LSResourceResolver` and `ErrorHandler`.

### validate

public void validate(Source source) throws SAXException, IOException
Validates the specified input.

This is just a convenience method for `validate(Source source, Result result)` with `result` of `null`.

Parameters:
  `source` - XML to be validated. Must be an XML document or XML element and must not be null. For backwards compatibility, the results of attempting to validate anything other than a document or element are implementation-dependent. Implementations must either recognize and process the input or throw an IllegalArgumentException.
Throws:
  `IllegalArgumentException` - If the `Source` is an XML artifact that the implementation cannot validate (for example, a processing instruction).
  `SAXException` - If the `ErrorHandler` throws a `SAXException` or if a fatal error is found and the `ErrorHandler` returns normally.
  `IOException` - If the validator is processing a `SAXSource` and the underlying `XMLReader` throws an `IOException`.
  `NullPointerException` - If `source` is `null`.
See Also:
  - `validate(Source source, Result result)`

### validate

public abstract void validate(Source source, Result result) throws SAXException, IOException
Validates the specified input and send the augmented validation result to the specified output.

This method places the following restrictions on the types of the `Source`/`Result` accepted.

`Source` / `Result` Accepted
| `StreamSource` | `SAXSource` | `DOMSource` | `StAXSource`
`null` | OK | OK | OK | OK
`StreamResult` | OK | `IllegalArgumentException` | `IllegalArgumentException` | `IllegalArgumentException`
`SAXResult` | `IllegalArgumentException` | OK | `IllegalArgumentException` | `IllegalArgumentException`
`DOMResult` | `IllegalArgumentException` | `IllegalArgumentException` | OK | `IllegalArgumentException`
`StAXResult` | `IllegalArgumentException` | `IllegalArgumentException` | `IllegalArgumentException` | OK

To validate one `Source` into another kind of `Result`, use the identity transformer (see `TransformerFactory.newTransformer()`).

Errors found during the validation is sent to the specified `ErrorHandler`.

If a document is valid, or if a document contains some errors but none of them were fatal and the `ErrorHandler` didn't throw any exception, then the method returns normally.

Parameters:
  `source` - XML to be validated. Must be an XML document or XML element and must not be null. For backwards compatibility, the results of attempting to validate anything other than a document or element are implementation-dependent. Implementations must either recognize and process the input or throw an IllegalArgumentException.
  `result` - The `Result` object that receives (possibly augmented) XML. This parameter can be null if the caller is not interested in it. Note that when a `DOMResult` is used, a validator might just pass the same DOM node from `DOMSource` to `DOMResult` (in which case `source.getNode()==result.getNode()`), it might copy the entire DOM tree, or it might alter the node given by the source.
Throws:
  `IllegalArgumentException` - If the `Result` type doesn't match the `Source` type or if the `Source` is an XML artifact that the implementation cannot validate (for example, a processing instruction).
  `SAXException` - If the `ErrorHandler` throws a `SAXException` or if a fatal error is found and the `ErrorHandler` returns normally.
  `IOException` - If the validator is processing a `SAXSource` and the underlying `XMLReader` throws an `IOException`.
  `NullPointerException` - If the `source` parameter is `null`.
See Also:
  - `validate(Source source)`

### setErrorHandler

public abstract void setErrorHandler(ErrorHandler errorHandler)
Sets the `ErrorHandler` to receive errors encountered during the `validate` method invocation.

Error handler can be used to customize the error handling process during a validation. When an `ErrorHandler` is set, errors found during the validation will be first sent to the `ErrorHandler`.

The error handler can abort further validation immediately by throwing `SAXException` from the handler. Or for example it can print an error to the screen and try to continue the validation by returning normally from the `ErrorHandler`

If any `Throwable` is thrown from an `ErrorHandler`, the caller of the `validate` method will be thrown the same `Throwable` object.

`Validator` is not allowed to throw `SAXException` without first reporting it to `ErrorHandler`.

When the `ErrorHandler` is null, the implementation will behave as if the following `ErrorHandler` is set:

    class DraconianErrorHandler implements ErrorHandler {
        public void fatalError( SAXParseException e ) throws SAXException {
            throw e;
        }
        public void error( SAXParseException e ) throws SAXException {
            throw e;
        }
        public void warning( SAXParseException e ) throws SAXException {
            // noop
        }
    }

When a new `Validator` object is created, initially this field is set to null.

Parameters:
  `errorHandler` - A new error handler to be set. This parameter can be null.

### getErrorHandler

public abstract ErrorHandler getErrorHandler()
Gets the current `ErrorHandler` set to this `Validator`.

Returns:
  This method returns the object that was last set through the `setErrorHandler(ErrorHandler)` method, or null if that method has never been called since this `Validator` has created.
See Also:
  - `setErrorHandler(ErrorHandler)`

### setResourceResolver

public abstract void setResourceResolver(LSResourceResolver resourceResolver)
Sets the `LSResourceResolver` to customize resource resolution while in a validation episode.

`Validator` uses a `LSResourceResolver` when it needs to locate external resources while a validation, although exactly what constitutes "locating external resources" is up to each schema language.

When the `LSResourceResolver` is null, the implementation will behave as if the following `LSResourceResolver` is set:

    class DumbLSResourceResolver implements LSResourceResolver {
        public LSInput resolveResource(
            String publicId, String systemId, String baseURI) {

            return null; // always return null
        }
    }

If a `LSResourceResolver` throws a `RuntimeException` (or instances of its derived classes), then the `Validator` will abort the parsing and the caller of the `validate` method will receive the same `RuntimeException`.

When a new `Validator` object is created, initially this field is set to null.

Parameters:
  `resourceResolver` - A new resource resolver to be set. This parameter can be null.

### getResourceResolver

public abstract LSResourceResolver getResourceResolver()
Gets the current `LSResourceResolver` set to this `Validator`.

Returns:
  This method returns the object that was last set through the `setResourceResolver(LSResourceResolver)` method, or null if that method has never been called since this `Validator` has created.
See Also:
  - `setErrorHandler(ErrorHandler)`

### getFeature

public boolean getFeature(String name) throws SAXNotRecognizedException, SAXNotSupportedException
Look up the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for a `Validator` to recognize a feature name but temporarily be unable to return its value. Some feature values may be available only in specific contexts, such as before, during, or after a validation.

Implementors are free (and encouraged) to invent their own features, using names built on their own URIs.

Parameters:
  `name` - The feature name, which is a non-null fully-qualified URI.
Returns:
  The current value of the feature (true or false).
Throws:
  `SAXNotRecognizedException` - If the feature value can't be assigned or retrieved.
  `SAXNotSupportedException` - When the `Validator` recognizes the feature name but cannot determine its value at this time.
  `NullPointerException` - When the name parameter is null.
See Also:
  - `setFeature(String, boolean)`

### setFeature

public void setFeature(String name, boolean value) throws SAXNotRecognizedException, SAXNotSupportedException
Set the value of a feature flag.

Feature can be used to control the way a `Validator` parses schemas, although `Validator`s are not required to recognize any specific feature names.

The feature name is any fully-qualified URI. It is possible for a `Validator` to expose a feature value but to be unable to change the current value. Some feature values may be immutable or mutable only in specific contexts, such as before, during, or after a validation.

Parameters:
  `name` - The feature name, which is a non-null fully-qualified URI.
  `value` - The requested value of the feature (true or false).
Throws:
  `SAXNotRecognizedException` - If the feature value can't be assigned or retrieved.
  `SAXNotSupportedException` - When the `Validator` recognizes the feature name but cannot set the requested value.
  `NullPointerException` - When the name parameter is null.
See Also:
  - `getFeature(String)`

### setProperty

public void setProperty(String name, Object object) throws SAXNotRecognizedException, SAXNotSupportedException
Set the value of a property.

The property name is any fully-qualified URI. It is possible for a `Validator` to recognize a property name but to be unable to change the current value. Some property values may be immutable or mutable only in specific contexts, such as before, during, or after a validation.

All implementations that implement JAXP 1.5 or newer are required to support the `XMLConstants.ACCESS_EXTERNAL_DTD` and `XMLConstants.ACCESS_EXTERNAL_SCHEMA` properties.

- Access to external DTDs in source or Schema file is restricted to the protocols specified by the `XMLConstants.ACCESS_EXTERNAL_DTD` property. If access is denied during validation due to the restriction of this property, `SAXException` will be thrown by the `validate(Source)` method.

  Access to external reference set by the schemaLocation attribute is restricted to the protocols specified by the `XMLConstants.ACCESS_EXTERNAL_SCHEMA` property. If access is denied during validation due to the restriction of this property, `SAXException` will be thrown by the `validate(Source)` method.

Parameters:
  `name` - The property name, which is a non-null fully-qualified URI.
  `object` - The requested value for the property.
Throws:
  `SAXNotRecognizedException` - If the property value can't be assigned or retrieved.
  `SAXNotSupportedException` - When the `Validator` recognizes the property name but cannot set the requested value.
  `NullPointerException` - When the name parameter is null.

### getProperty

public Object getProperty(String name) throws SAXNotRecognizedException, SAXNotSupportedException
Look up the value of a property.

The property name is any fully-qualified URI. It is possible for a `Validator` to recognize a property name but temporarily be unable to return its value. Some property values may be available only in specific contexts, such as before, during, or after a validation.

`Validator`s are not required to recognize any specific property names.

Implementors are free (and encouraged) to invent their own properties, using names built on their own URIs.

Parameters:
  `name` - The property name, which is a non-null fully-qualified URI.
Returns:
  The current value of the property.
Throws:
  `SAXNotRecognizedException` - If the property value can't be assigned or retrieved.
  `SAXNotSupportedException` - When the XMLReader recognizes the property name but cannot determine its value at this time.
  `NullPointerException` - When the name parameter is null.
See Also:
  - `setProperty(String, Object)`