org.omnifaces.el.ScopedRunner Maven / Gradle / Ivy
/*
* Copyright 2020 OmniFaces
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.omnifaces.el;
import java.util.HashMap;
import java.util.Map;
import javax.faces.context.FacesContext;
import org.omnifaces.util.Callback;
/**
* This class helps in letting code run within its own scope. Such scope is defined by specific variables being
* available to EL within it. The request scope is used to store the variables.
*
* @author Arjan Tijms
*
*/
public class ScopedRunner {
private FacesContext context;
private Map scopedVariables;
private Map previousVariables = new HashMap<>();
public ScopedRunner(FacesContext context) {
this(context, new HashMap());
}
public ScopedRunner(FacesContext context, Map scopedVariables) {
this.context = context;
this.scopedVariables = scopedVariables;
}
/**
* Adds the given variable to this instance. Can be used in a builder-pattern.
*
* @param key the key name of the variable
* @param value the value of the variable
* @return this ScopedRunner, so adding variables and finally calling invoke can be chained.
*/
public ScopedRunner with(String key, Object value) {
scopedVariables.put(key, value);
return this;
}
/**
* Invokes the callback within the scope of the variables being given in the constructor.
* @param callback The callback.
*/
public void invoke(Callback.Void callback) {
try {
setNewScope();
callback.invoke();
} finally {
restorePreviousScope();
}
}
private void setNewScope() {
previousVariables.clear();
Map requestMap = context.getExternalContext().getRequestMap();
for (Map.Entry entry : scopedVariables.entrySet()) {
Object previousVariable = requestMap.put(entry.getKey(), entry.getValue());
if (previousVariable != null) {
previousVariables.put(entry.getKey(), previousVariable);
}
}
}
private void restorePreviousScope() {
try {
Map requestMap = context.getExternalContext().getRequestMap();
for (Map.Entry entry : scopedVariables.entrySet()) {
Object previousVariable = previousVariables.get(entry.getKey());
if (previousVariable != null) {
requestMap.put(entry.getKey(), previousVariable);
} else {
requestMap.remove(entry.getKey());
}
}
} finally {
previousVariables.clear();
}
}
/**
* Invokes the callback within the scope of the given variable.
* @param context The involved faces context.
* @param key the key name of the variable
* @param value the value of the variable
* @param callback The callback.
* @since 3.0
*/
public static void forEach(FacesContext context, String key, Object value, Runnable callback) {
new ScopedRunner(context).with(key, value).invoke(callback::run);
}
}