org.springframework.web.servlet.tags.EvalTag Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* 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.springframework.web.servlet.tags;
import java.io.IOException;
import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.PageContext;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.context.expression.EnvironmentAccessor;
import org.springframework.context.expression.MapAccessor;
import org.springframework.core.convert.ConversionService;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.expression.spel.support.StandardTypeConverter;
import org.springframework.lang.Nullable;
import org.springframework.util.ObjectUtils;
import org.springframework.web.util.JavaScriptUtils;
import org.springframework.web.util.TagUtils;
/**
* The {@code } tag evaluates a Spring expression (SpEL) and either prints
* the result or assigns it to a variable. Supports the standard JSP evaluation
* context consisting of implicit variables and scoped attributes.
*
*
* Attribute Summary
*
*
* Attribute
* Required?
* Runtime Expression?
* Description
*
*
*
*
* expression
* true
* true
* The expression to evaluate.
*
*
* htmlEscape
* false
* true
* Set HTML escaping for this tag, as a boolean value.
* Overrides the default HTML escaping setting for the current page.
*
*
* javaScriptEscape
* false
* true
* Set JavaScript escaping for this tag, as a boolean value.
* Default is {@code false}.
*
*
* scope
* false
* true
* The scope for the var. 'application', 'session', 'request' and 'page'
* scopes are supported. Defaults to page scope. This attribute has no effect
* unless the var attribute is also defined.
*
*
* var
* false
* true
* The name of the variable to export the evaluation result to.
* If not specified the evaluation result is converted to a String and written
* as output.
*
*
*
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 3.0.1
*/
@SuppressWarnings("serial")
public class EvalTag extends HtmlEscapingAwareTag {
/**
* {@link jakarta.servlet.jsp.PageContext} attribute for the
* page-level {@link EvaluationContext} instance.
*/
private static final String EVALUATION_CONTEXT_PAGE_ATTRIBUTE =
"org.springframework.web.servlet.tags.EVALUATION_CONTEXT";
private final ExpressionParser expressionParser = new SpelExpressionParser();
@Nullable
private Expression expression;
@Nullable
private String var;
private int scope = PageContext.PAGE_SCOPE;
private boolean javaScriptEscape = false;
/**
* Set the expression to evaluate.
*/
public void setExpression(String expression) {
this.expression = this.expressionParser.parseExpression(expression);
}
/**
* Set the variable name to expose the evaluation result under.
* Defaults to rendering the result to the current JspWriter.
*/
public void setVar(String var) {
this.var = var;
}
/**
* Set the scope to export the evaluation result to.
* This attribute has no meaning unless var is also defined.
*/
public void setScope(String scope) {
this.scope = TagUtils.getScope(scope);
}
/**
* Set JavaScript escaping for this tag, as boolean value.
* Default is "false".
*/
public void setJavaScriptEscape(boolean javaScriptEscape) throws JspException {
this.javaScriptEscape = javaScriptEscape;
}
@Override
public int doStartTagInternal() throws JspException {
return EVAL_BODY_INCLUDE;
}
@Override
public int doEndTag() throws JspException {
EvaluationContext evaluationContext =
(EvaluationContext) this.pageContext.getAttribute(EVALUATION_CONTEXT_PAGE_ATTRIBUTE);
if (evaluationContext == null) {
evaluationContext = createEvaluationContext(this.pageContext);
this.pageContext.setAttribute(EVALUATION_CONTEXT_PAGE_ATTRIBUTE, evaluationContext);
}
if (this.var != null) {
Object result = (this.expression != null ? this.expression.getValue(evaluationContext) : null);
this.pageContext.setAttribute(this.var, result, this.scope);
}
else {
try {
String result = (this.expression != null ?
this.expression.getValue(evaluationContext, String.class) : null);
result = ObjectUtils.getDisplayString(result);
result = htmlEscape(result);
result = (this.javaScriptEscape ? JavaScriptUtils.javaScriptEscape(result) : result);
this.pageContext.getOut().print(result);
}
catch (IOException ex) {
throw new JspException(ex);
}
}
return EVAL_PAGE;
}
private EvaluationContext createEvaluationContext(PageContext pageContext) {
StandardEvaluationContext context = new StandardEvaluationContext();
context.addPropertyAccessor(new JspPropertyAccessor(pageContext));
context.addPropertyAccessor(new MapAccessor());
context.addPropertyAccessor(new EnvironmentAccessor());
context.setBeanResolver(new BeanFactoryResolver(getRequestContext().getWebApplicationContext()));
ConversionService conversionService = getConversionService(pageContext);
if (conversionService != null) {
context.setTypeConverter(new StandardTypeConverter(conversionService));
}
return context;
}
@Nullable
private ConversionService getConversionService(PageContext pageContext) {
return (ConversionService) pageContext.getRequest().getAttribute(ConversionService.class.getName());
}
@SuppressWarnings("deprecation")
private static class JspPropertyAccessor implements PropertyAccessor {
private final PageContext pageContext;
@Nullable
private final jakarta.servlet.jsp.el.VariableResolver variableResolver;
public JspPropertyAccessor(PageContext pageContext) {
this.pageContext = pageContext;
this.variableResolver = pageContext.getVariableResolver();
}
@Override
@Nullable
public Class[] getSpecificTargetClasses() {
return null;
}
@Override
public boolean canRead(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
return (target == null &&
(resolveImplicitVariable(name) != null || this.pageContext.findAttribute(name) != null));
}
@Override
public TypedValue read(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
Object implicitVar = resolveImplicitVariable(name);
if (implicitVar != null) {
return new TypedValue(implicitVar);
}
return new TypedValue(this.pageContext.findAttribute(name));
}
@Override
public boolean canWrite(EvaluationContext context, @Nullable Object target, String name) {
return false;
}
@Override
public void write(EvaluationContext context, @Nullable Object target, String name, @Nullable Object newValue) {
throw new UnsupportedOperationException();
}
@Nullable
private Object resolveImplicitVariable(String name) throws AccessException {
if (this.variableResolver == null) {
return null;
}
try {
return this.variableResolver.resolveVariable(name);
}
catch (Exception ex) {
throw new AccessException(
"Unexpected exception occurred accessing '" + name + "' as an implicit variable", ex);
}
}
}
}