javax.el.BeanNameELResolver Maven / Gradle / Ivy
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package javax.el;
import java.util.Iterator;
import java.beans.FeatureDescriptor;
/**
* An ELResolver for resolving user or container managed beans.
* A {@link BeanNameResolver} is required for its proper operation.
* The following example creates an ELResolver that
* resolves the name "bean" to an instance of MyBean.
*
*
* ELResovler elr = new BeanNameELResolver(new BeanNameResolver {
* public boolean isNameResolved(String beanName) {
* return "bean".equals(beanName);
* }
* public Object getBean(String beanName) {
* return "bean".equals(beanName)? new MyBean(): null;
* }
* });
*
*
*
* @since EL 3.0
*/
public class BeanNameELResolver extends ELResolver {
private BeanNameResolver beanNameResolver;
/**
* Constructor
* @param beanNameResolver The {@link BeanNameResolver} that resolves a bean name.
*/
public BeanNameELResolver(BeanNameResolver beanNameResolver) {
this.beanNameResolver = beanNameResolver;
}
/**
* If the base object is null and the property is a name
* that is resolvable by the BeanNameResolver, returns the value
* resolved by the BeanNameResolver.
*
* If name is resolved by the BeanNameResolver, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base null
* @param property The name of the bean.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the value of the bean with the given name. Otherwise, undefined.
* @throws NullPointerException if context is null.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null && property instanceof String) {
if (beanNameResolver.isNameResolved((String) property)) {
context.setPropertyResolved(base, property);
return beanNameResolver.getBean((String) property);
}
}
return null;
}
/**
* If the base is null and the property is a name that is resolvable by
* the BeanNameResolver, the bean in the BeanNameResolver is set to the
* given value.
*
* If the name is resolvable by the BeanNameResolver, or if the
* BeanNameResolver allows creating a new bean,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller can
* safely assume no value has been set.
*
* @param context The context of this evaluation.
* @param base null
* @param property The name of the bean
* @param value The value to set the bean with the given name to.
* @throws NullPointerException if context is null
* @throws PropertyNotWritableException if the BeanNameResolver does not
* allow the bean to be modified.
* @throws ELException if an exception was thrown while attempting to
* set the bean with the given name. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
@Override
public void setValue(ELContext context, Object base, Object property,
Object value) {
if (context == null) {
throw new NullPointerException();
}
if (base == null && property instanceof String) {
String beanName = (String) property;
if (beanNameResolver.isNameResolved(beanName) ||
beanNameResolver.canCreateBean(beanName)) {
beanNameResolver.setBeanValue(beanName, value);
context.setPropertyResolved(base, property);
}
}
}
/**
* If the base is null and the property is a name resolvable by
* the BeanNameResolver, return the type of the bean.
*
* If the name is resolvable by the BeanNameResolver,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller can
* safely assume no value has been set.
*
* @param context The context of this evaluation.
* @param base null
* @param property The name of the bean.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the type of the bean with the given name. Otherwise, undefined.
* @throws NullPointerException if context is null.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
@Override
public Class getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null && property instanceof String) {
if (beanNameResolver.isNameResolved((String) property)) {
context.setPropertyResolved(true);
return beanNameResolver.getBean((String) property).getClass();
}
}
return null;
}
/**
* If the base is null and the property is a name resolvable by
* the BeanNameResolver, attempts to determine if the bean is writable.
*
* If the name is resolvable by the BeanNameResolver,
* the propertyResolved property of the
* ELContext object must be set to true
* by the resolver, before returning. If this property is not
* true after this method is called, the caller can
* safely assume no value has been set.
*
* @param context The context of this evaluation.
* @param base null
* @param property The name of the bean.
* @return If the propertyResolved property of
* ELContext was set to true, then
* true if the property is read-only or
* false if not; otherwise undefined.
* @throws NullPointerException if context is null.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null && property instanceof String) {
if (beanNameResolver.isNameResolved((String) property)) {
context.setPropertyResolved(true);
return beanNameResolver.isReadOnly((String) property);
}
}
return false;
}
/**
* Always returns null, since there is no reason to
* iterate through a list of one element: bean name.
* @param context The context of this evaluation.
* @param base null.
* @return null.
*/
public Iterator getFeatureDescriptors(
ELContext context, Object base) {
return null;
}
/**
* Always returns String.class, since a bean name is a String.
* @param context The context of this evaluation.
* @param base null.
* @return String.class.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
return String.class;
}
}
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