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https://issues.apache.org/jira/browse/SLING-577?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Trott updated SLING-577:
------------------------------
Attachment: evalproperty.patch
Patch file
> Patch Submission: JSP tag to evaluate JCR properties using EL
> -------------------------------------------------------------
>
> Key: SLING-577
> URL: https://issues.apache.org/jira/browse/SLING-577
> Project: Sling
> Issue Type: New Feature
> Components: Scripting JSP
> Reporter: David Trott
> Attachments: evalproperty.patch
>
>
> Use case
> ========
> Say you are building components in sling and you want to break the logic into
> two separate components:
> - One to fetch the data (possibly from a DB) and populate the pageContext.
> - And one to render some HTML using data in the pageContext.
>
> This would allow either component to be switched out without affecting the
> other.
>
> In this scenario we need a way to connect the two components together; one
> option is to use EL
> Hence we could define a property of the content node for the visual
> component: rating="${dbrating}"
> This assumes that the DB component has already done a
> pageContext.setAttribute("dbrating", "some value");
> We can then build a JSP page which evaluates the properties, e.g:
> <h1>Current Rating: '<sling:evalProperty property="rating"/>'</h1>
> Hence this JSP page would form the core of the visual component.
> Patch File
> ========
> diff -Nur
> jsp-taglib-base/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTEI.java
>
> jsp-taglib-update/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTEI.java
> ---
> jsp-taglib-base/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTEI.java
> 1969-12-31 16:00:00.000000000 -0800
> +++
> jsp-taglib-update/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTEI.java
> 2008-07-22 20:25:57.000000000 -0700
> @@ -0,0 +1,74 @@
> +/*
> + * Licensed to the Apache Software Foundation (ASF) under one or more
> + * contributor license agreements. See the NOTICE file distributed with
> + * this work for additional information regarding copyright ownership.
> + * The ASF licenses this file to You 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.sling.scripting.jsp.taglib;
> +
> +import static
> org.apache.sling.scripting.jsp.taglib.EvalPropertyTag.DEFAULT_VAR;
> +
> +import java.util.ArrayList;
> +import java.util.List;
> +
> +import javax.servlet.jsp.tagext.TagData;
> +import javax.servlet.jsp.tagext.TagExtraInfo;
> +import javax.servlet.jsp.tagext.VariableInfo;
> +
> +/**
> + * This class defines the scripting variables that are created by the
> + * <code>EvalPropertyTag</code>.
> + */
> +public class EvalPropertyTEI extends TagExtraInfo {
> +
> + /**
> + * The name of the tag attribute used to define the name of the
> + * value scripting variable (value is "var").
> + */
> + public static final String ATTR_VAR = "var";
> +
> + private static final String VAR_CLASS = String.class.getName();
> +
> + /**
> + * Returns an Array of <code>VariableInfo</code> objects describing
> + * scripting variables.
> + *
> + * @see javax.servlet.jsp.tagext.TagExtraInfo#getVariableInfo(TagData)
> + */
> + public VariableInfo[] getVariableInfo(TagData data) {
> +
> + List<VariableInfo> varInfos = new ArrayList<VariableInfo>();
> +
> + addVar(varInfos, data, ATTR_VAR, DEFAULT_VAR, VAR_CLASS);
> +
> + return varInfos.toArray(new VariableInfo[varInfos.size()]);
> +
> + }
> +
> + private void addVar(List<VariableInfo> varInfos, TagData data, String
> attrName, String defaultValue, String varClass) {
> + String value = getValue(data, attrName, defaultValue);
> +
> + if (value != null && varClass != null) {
> + varInfos.add(new VariableInfo(value, varClass, true,
> VariableInfo.AT_END));
> + }
> + }
> +
> + private String getValue(TagData data, String name, String defaultValue) {
> + Object value = data.getAttribute(name);
> + if (value instanceof String) {
> + return (String) value;
> + }
> +
> + return defaultValue;
> + }
> +}
> diff -Nur
> jsp-taglib-base/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTag.java
>
> jsp-taglib-update/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTag.java
> ---
> jsp-taglib-base/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTag.java
> 1969-12-31 16:00:00.000000000 -0800
> +++
> jsp-taglib-update/src/main/java/org/apache/sling/scripting/jsp/taglib/EvalPropertyTag.java
> 2008-07-22 20:25:57.000000000 -0700
> @@ -0,0 +1,137 @@
> +/*
> + * Licensed to the Apache Software Foundation (ASF) under one or more
> + * contributor license agreements. See the NOTICE file distributed with
> + * this work for additional information regarding copyright ownership.
> + * The ASF licenses this file to You 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.sling.scripting.jsp.taglib;
> +
> +import java.io.IOException;
> +
> +import javax.el.ELContext;
> +import javax.el.ExpressionFactory;
> +import javax.jcr.Node;
> +import javax.jcr.PathNotFoundException;
> +import javax.jcr.Property;
> +import javax.jcr.RepositoryException;
> +import javax.servlet.ServletRequest;
> +import javax.servlet.jsp.JspException;
> +import javax.servlet.jsp.JspFactory;
> +import javax.servlet.jsp.tagext.TagSupport;
> +
> +import org.apache.sling.api.resource.Resource;
> +import org.apache.sling.api.resource.ResourceResolver;
> +import org.apache.sling.api.scripting.SlingBindings;
> +import org.apache.sling.api.scripting.SlingScriptHelper;
> +
> +/**
> + * The <code>EvalPropertyTag</code> implements the
> + * <code><sling:evalProperty></code> custom tag.
> + */
> +public class EvalPropertyTag extends TagSupport {
> +
> + /**
> + * Default name for the scripting variable set to the result
> + * of the evaluation (value is null).
> + */
> + public static final String DEFAULT_VAR = null;
> +
> + /**
> + * The default path if no path attribute is passed to the tag (value is
> ".").
> + */
> + public static final String DEFAULT_PATH = ".";
> +
> + private String var = DEFAULT_VAR;
> +
> + private String path = DEFAULT_PATH;
> +
> + private String property;
> +
> + /**
> + * Default constructor.
> + */
> + public EvalPropertyTag() {
> + }
> +
> + /**
> + * Reads a value from the performs an EL evaluation and sets a variable.
> + *
> + * @return always [EMAIL PROTECTED] #EVAL_PAGE}.
> + */
> + public int doEndTag() throws JspException {
> + try {
> + final ServletRequest request = pageContext.getRequest();
> + final SlingBindings bindings =
> (SlingBindings)request.getAttribute(SlingBindings.class.getName());
> + final SlingScriptHelper scriptHelper = bindings.getSling();
> + final Resource baseResource =
> scriptHelper.getRequest().getResource();
> + final ResourceResolver resourceResolver =
> baseResource.getResourceResolver();
> +
> + final Resource resource =
> resourceResolver.getResource(baseResource, this.path);
> + if (resource == null) {
> + throw new JspException("Resource not found: " + this.path);
> + }
> +
> + final Node node = resource.adaptTo(Node.class);
> + if (node == null) {
> + throw new JspException("Path is not a valid node: " +
> this.path);
> + }
> +
> + final Property propNode = node.getProperty(this.property);
> + if (propNode == node) {
> + throw new JspException("Property not found: " + this.path);
> + }
> +
> +
> + final String elValue = propNode.getString();
> + if (elValue != null) {
> + ELContext elctx = pageContext.getELContext();
> + String strValue = (String)
> getExpressionFactory().createValueExpression(elctx, elValue,
> String.class).getValue(elctx);
> +
> + if (this.var == null || this.var.trim().equals("")) {
> + pageContext.getOut().print(strValue);
> + } else {
> + pageContext.setAttribute(this.var, strValue);
> + }
> + }
> +
> + return EVAL_PAGE;
> + } catch (PathNotFoundException e) {
> + throw new JspException(e);
> + } catch (RepositoryException e) {
> + throw new JspException(e);
> + } catch (IOException e) {
> + throw new JspException(e);
> + }
> + }
> +
> + // --------------------------< setter methods
> >----------------------------
> +
> + public void setVar(String var) {
> + this.var = var;
> + }
> +
> + public void setPath(String path) {
> + this.path = path;
> + }
> +
> + public void setProperty(String property) {
> + this.property = property;
> + }
> +
> + private ExpressionFactory getExpressionFactory() {
> + return JspFactory.getDefaultFactory()
> + .getJspApplicationContext(pageContext.getServletContext())
> + .getExpressionFactory();
> +
> + }
> +}
> diff -Nur jsp-taglib-base/src/main/resources/META-INF/taglib.tld
> jsp-taglib-update/src/main/resources/META-INF/taglib.tld
> --- jsp-taglib-base/src/main/resources/META-INF/taglib.tld 2008-07-22
> 20:21:56.000000000 -0700
> +++ jsp-taglib-update/src/main/resources/META-INF/taglib.tld 2008-07-22
> 20:25:57.000000000 -0700
> @@ -161,4 +161,43 @@
> </attribute>
> </tag>
>
> + <tag>
> + <description>
> + Performs an EL evaluation on the value in a JCR property.
> + </description>
> + <name>evalProperty</name>
> + <tag-class>
> + org.apache.sling.scripting.jsp.taglib.EvalPropertyTag
> + </tag-class>
> + <tei-class>
> + org.apache.sling.scripting.jsp.taglib.EvalPropertyTEI
> + </tei-class>
> + <body-content>empty</body-content>
> + <attribute>
> + <description>
> + The variable which receives the result of the evaluation.
> + If this attribute is missing or blank the result is written
> to out.
> + </description>
> + <name>var</name>
> + <required>false</required>
> + <rtexprvalue>false</rtexprvalue>
> + </attribute>
> + <attribute>
> + <description>
> + The relative path to the node which has the property to be
> evaluated.
> + If omitted the tag will use "." (current content node).
> + </description>
> + <name>path</name>
> + <required>false</required>
> + <rtexprvalue>true</rtexprvalue>
> + </attribute>
> + <attribute>
> + <description>
> + The property to be evaluated.
> + </description>
> + <name>property</name>
> + <required>true</required>
> + <rtexprvalue>true</rtexprvalue>
> + </attribute>
> + </tag>
> </taglib>
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