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@beikov
Created Nov 20, 2013
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import java.beans.FeatureDescriptor;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.el.ArrayELResolver;
import javax.el.BeanELResolver;
import javax.el.CompositeELResolver;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.ExpressionFactory;
import javax.el.FunctionMapper;
import javax.el.ListELResolver;
import javax.el.MapELResolver;
import javax.el.PropertyNotFoundException;
import javax.el.PropertyNotWritableException;
import javax.el.ValueExpression;
import javax.el.VariableMapper;
import org.apache.deltaspike.core.api.provider.BeanManagerProvider;
/**
* @author Christian Beikov
*/
public class ELUtils {
private ELUtils() {
}
@SuppressWarnings("unchecked")
public static <T> T getValueSimple(String expression, Class<T> expectedType,
Map<String, Object> variables) {
ExpressionFactory ef = ExpressionFactory.newInstance();
ELContext elContext = new SimpleContext(variables, ef, new SimpleELResolver());
return (T) ef
.createValueExpression(elContext, expression, expectedType)
.getValue(elContext);
}
@SuppressWarnings("unchecked")
public static <T> T getValue(String expression, Class<T> expectedType,
Map<String, Object> variables) {
ExpressionFactory ef = ExpressionFactory.newInstance();
ELContext elContext = new SimpleContext(variables, ef, new FullELResolver());
return (T) ef
.createValueExpression(elContext, expression, expectedType)
.getValue(elContext);
}
@SuppressWarnings("unchecked")
public static <T> T getValue(String expression, Class<T> expectedType,
Map<String, Object> variables, ELResolver elResolver) {
ExpressionFactory ef = ExpressionFactory.newInstance();
ELContext elContext = new SimpleContext(variables, ef, elResolver);
return (T) ef
.createValueExpression(elContext, expression, expectedType)
.getValue(elContext);
}
public static ELResolver getCdiAwareELResolver() {
return new FullELResolver(BeanManagerProvider.getInstance().getBeanManager().getELResolver());
}
private static class SimpleContext extends ELContext {
private final VariableMapper variables = new VariableMapper() {
Map<String, ValueExpression> map = new HashMap<String, ValueExpression>();
@Override
public ValueExpression resolveVariable(String variable) {
return map.get(variable);
}
@Override
public ValueExpression setVariable(String variable,
ValueExpression expression) {
return map.put(variable, expression);
}
};
private final ELResolver resolver;
public SimpleContext(Map<String, Object> map, ExpressionFactory ef, ELResolver elResolver) {
this.resolver = elResolver;
if (map != null && !map.isEmpty()) {
for (Map.Entry<String, Object> entry : map.entrySet()) {
if (entry.getValue() instanceof ValueExpression) {
variables.setVariable(entry.getKey(),
(ValueExpression) entry.getValue());
} else {
variables.setVariable(entry.getKey(), ef
.createValueExpression(entry.getValue(), entry
.getValue().getClass()));
}
}
}
}
@Override
public FunctionMapper getFunctionMapper() {
return null;
}
@Override
public VariableMapper getVariableMapper() {
return variables;
}
@Override
public ELResolver getELResolver() {
return resolver;
}
}
private static class SimpleELResolver extends ELResolver{
private boolean isResolvable(Object base) {
return base == null;
}
private boolean resolve(ELContext context, Object base,
Object property) {
context.setPropertyResolved(isResolvable(base)
&& property instanceof String);
return context.isPropertyResolved();
}
@Override
public Class<?> getCommonPropertyType(ELContext context, Object base) {
return isResolvable(context) ? String.class : null;
}
@Override
public Iterator<FeatureDescriptor> getFeatureDescriptors(
ELContext context, Object base) {
return null;
}
@Override
public Class<?> getType(ELContext context, Object base,
Object property) {
return resolve(context, base, property) ? Object.class : null;
}
@Override
public Object getValue(ELContext context, Object base,
Object property) {
return null;
}
@Override
public boolean isReadOnly(ELContext context, Object base,
Object property) {
return resolve(context, base, property) ? true : false;
}
@Override
public void setValue(ELContext context, Object base,
Object property, Object value)
throws PropertyNotWritableException {
throw new PropertyNotWritableException("Resolver is read only!");
}
@Override
public Object invoke(ELContext context, Object base, Object method,
Class<?>[] paramTypes, Object[] params) {
if (resolve(context, base, method)) {
throw new NullPointerException("Cannot invoke method "
+ method + " on null");
}
return null;
}
}
private static class FullELResolver extends ELResolver{
private final CompositeELResolver delegate;
public FullELResolver() {
delegate = new CompositeELResolver();
delegate.add(new ArrayELResolver(true));
delegate.add(new ListELResolver(true));
delegate.add(new MapELResolver(true));
delegate.add(new BeanELResolver(true));
}
public FullELResolver(ELResolver resolver) {
delegate = new CompositeELResolver();
delegate.add(new ArrayELResolver(true));
delegate.add(new ListELResolver(true));
delegate.add(new MapELResolver(true));
delegate.add(new BeanELResolver(true));
delegate.add(resolver);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
@Override
public Object getValue(ELContext context, Object base, Object property)
throws NullPointerException, PropertyNotFoundException,
ELException {
return delegate.getValue(context, base, property);
}
@Override
public void setValue(ELContext context, Object base, Object property,
Object value) throws NullPointerException,
PropertyNotFoundException, PropertyNotWritableException,
ELException {
delegate.setValue(context, base, property, value);
}
@Override
public boolean isReadOnly(ELContext context, Object base,
Object property) throws NullPointerException,
PropertyNotFoundException, ELException {
return delegate.isReadOnly(context, base, property);
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public Iterator<FeatureDescriptor> getFeatureDescriptors(
ELContext context, Object base) {
return delegate.getFeatureDescriptors(context, base);
}
@Override
public Class<?> getCommonPropertyType(ELContext context, Object base) {
return delegate.getCommonPropertyType(context, base);
}
@Override
public Class<?> getType(ELContext context, Object base, Object property)
throws NullPointerException, PropertyNotFoundException,
ELException {
return delegate.getType(context, base, property);
}
@Override
public Object invoke(ELContext context, Object base, Object method,
Class<?>[] paramTypes, Object[] params) {
return delegate.invoke(context, base, method, paramTypes, params);
}
@Override
public String toString() {
return delegate.toString();
}
}
}
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