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Jakarta Standard Tag Library Implementation
/*
* Copyright (c) 1997-2020 Oracle and/or its affiliates. All rights reserved.
* Copyright 2004 The Apache Software Foundation
*
* 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
*
* http://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.apache.taglibs.standard.tag.el.core;
import jakarta.servlet.jsp.JspException;
import org.apache.taglibs.standard.tag.common.core.ImportSupport;
import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
/**
* A handler for <import> that accepts attributes as Strings
* and evaluates them as expressions at runtime.
*
* @author Shawn Bayern
*/
public class ImportTag extends ImportSupport {
//*********************************************************************
// 'Private' state (implementation details)
private String context_; // stores EL-based property
private String charEncoding_; // stores EL-based property
private String url_; // stores EL-based property
//*********************************************************************
// Constructor
/**
* Constructs a new ImportTag. As with TagSupport, subclasses
* should not provide other constructors and are expected to call
* the superclass constructor
*/
public ImportTag() {
super();
init();
}
//*********************************************************************
// Tag logic
// evaluates expression and chains to parent
public int doStartTag() throws JspException {
// evaluate any expressions we were passed, once per invocation
evaluateExpressions();
// chain to the parent implementation
return super.doStartTag();
}
// Releases any resources we may have (or inherit)
public void release() {
super.release();
init();
}
//*********************************************************************
// Accessor methods
// for EL-based attribute
public void setUrl(String url_) {
this.url_ = url_;
}
public void setContext(String context_) {
this.context_ = context_;
}
public void setCharEncoding(String charEncoding_) {
this.charEncoding_ = charEncoding_;
}
//*********************************************************************
// Private (utility) methods
// (re)initializes state (during release() or construction)
private void init() {
// null implies "no expression"
url_ = context_ = charEncoding_ = null;
}
/* Evaluates expressions as necessary */
private void evaluateExpressions() throws JspException {
/*
* Note: we don't check for type mismatches here; we assume
* the expression evaluator will return the expected type
* (by virtue of knowledge we give it about what that type is).
* A ClassCastException here is truly unexpected, so we let it
* propagate up.
*/
url = (String) ExpressionUtil.evalNotNull(
"import", "url", url_, String.class, this, pageContext);
if (url == null || url.equals(""))
throw new NullAttributeException("import", "url");
context = (String) ExpressionUtil.evalNotNull(
"import", "context", context_, String.class, this, pageContext);
charEncoding = (String) ExpressionUtil.evalNotNull(
"import", "charEncoding", charEncoding_, String.class, this,
pageContext);
}
}