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Tomcat example source code file (Set.java)

This example Tomcat source code file (Set.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

illegalaccessexception, invalid, jspexception, jspexception, no, object, object, set, string, string, tagplugin, tagplugin

The Tomcat Set.java source code

/*
 * 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.jasper.tagplugins.jstl.core;

import org.apache.jasper.compiler.tagplugin.TagPlugin;
import org.apache.jasper.compiler.tagplugin.TagPluginContext;
import org.apache.jasper.tagplugins.jstl.Util;

public class Set implements TagPlugin {
    
    public void doTag(TagPluginContext ctxt) {
        
        //the flags to indicate whether the attributes have been specified
        boolean hasValue = false, hasVar = false, hasScope = false, 
        hasTarget = false;
        
        //the scope name
        String strScope;
        //the id of the scope
        int iScope;
        
        //initialize the flags
        hasValue = ctxt.isAttributeSpecified("value");
        hasVar = ctxt.isAttributeSpecified("var");
        hasScope = ctxt.isAttributeSpecified("scope");
        hasTarget = ctxt.isAttributeSpecified("target");
        
        //the temp variables name
        String resultName = ctxt.getTemporaryVariableName();
        String targetName = ctxt.getTemporaryVariableName();
        String propertyName = ctxt.getTemporaryVariableName();
        
        //initialize the "result" which will be assigned to the var or target.property
        ctxt.generateJavaSource("Object " + resultName + " = null;");
        if(hasValue){
            ctxt.generateJavaSource(resultName + " = ");
            ctxt.generateAttribute("value");
            ctxt.generateJavaSource(";");
        }else{
            ctxt.dontUseTagPlugin();
            return;
        }
        
        //initialize the strScope
        if(hasScope){
            strScope = ctxt.getConstantAttribute("scope");
        }else{
            strScope = "page";
        }
        
        //get the iScope according to the strScope
        iScope = Util.getScope(strScope);
        
        //if the attribute var has been specified then assign the result to the var;
        if(hasVar){
            String strVar = ctxt.getConstantAttribute("var");
            ctxt.generateJavaSource("if(null != " + resultName + "){");
            ctxt.generateJavaSource("    pageContext.setAttribute(\"" + strVar + "\"," + resultName + "," + iScope + ");");
            ctxt.generateJavaSource("} else {");
            if(hasScope){
                ctxt.generateJavaSource("    pageContext.removeAttribute(\"" + strVar + "\"," + iScope + ");");
            }else{
                ctxt.generateJavaSource("    pageContext.removeAttribute(\"" + strVar + "\");");
            }
            ctxt.generateJavaSource("}");
            
            //else assign the result to the target.property
        }else if(hasTarget){
            
            //generate the temp variable name
            String pdName = ctxt.getTemporaryVariableName();
            String successFlagName = ctxt.getTemporaryVariableName();
            String index = ctxt.getTemporaryVariableName();
            String methodName = ctxt.getTemporaryVariableName();
            
            //initialize the property
            ctxt.generateJavaSource("String " + propertyName + " = null;");
            ctxt.generateJavaSource("if(");
            ctxt.generateAttribute("property");
            ctxt.generateJavaSource(" != null){");
            ctxt.generateJavaSource("    " + propertyName + " = (");
            ctxt.generateAttribute("property");
            ctxt.generateJavaSource(").toString();");
            ctxt.generateJavaSource("}");
            
            //initialize the target
            ctxt.generateJavaSource("Object " + targetName + " = ");
            ctxt.generateAttribute("target");
            ctxt.generateJavaSource(";");
            
            //the target is ok
            ctxt.generateJavaSource("if(" + targetName + " != null){");
            
            //if the target is a map, then put the result into the map with the key property
            ctxt.generateJavaSource("    if(" + targetName + " instanceof java.util.Map){");
            ctxt.generateJavaSource("        if(null != " + resultName + "){");
            ctxt.generateJavaSource("            ((java.util.Map) " + targetName + ").put(" + propertyName + "," + resultName + ");");
            ctxt.generateJavaSource("        }else{");
            ctxt.generateJavaSource("            ((java.util.Map) " + targetName + ").remove(" + propertyName + ");");
            ctxt.generateJavaSource("        }");
            
            //else assign the result to the target.property
            ctxt.generateJavaSource("    }else{");
            ctxt.generateJavaSource("        try{");
            
            //get all the property of the target
            ctxt.generateJavaSource("            java.beans.PropertyDescriptor " + pdName + "[] = java.beans.Introspector.getBeanInfo(" + targetName + ".getClass()).getPropertyDescriptors();");
            
            //the success flag is to imply whether the assign is successful
            ctxt.generateJavaSource("            boolean " + successFlagName + " = false;");
            
            //find the right property
            ctxt.generateJavaSource("            for(int " + index + "=0;" + index + "<" + pdName + ".length;" + index + "++){");
            ctxt.generateJavaSource("                if(" + pdName + "[" + index + "].getName().equals(" + propertyName + ")){");
            
            //get the "set" method;
            ctxt.generateJavaSource("                    java.lang.reflect.Method " + methodName + " = " + pdName + "[" + index + "].getWriteMethod();");
            ctxt.generateJavaSource("                    if(null == " + methodName + "){");
            ctxt.generateJavaSource("                        throw new JspException(\"No setter method in <set> for property \"+" + propertyName + ");");
            ctxt.generateJavaSource("                    }");
            
            //invoke the method through the reflection
            ctxt.generateJavaSource("                    if(" + resultName + " != null){");
            ctxt.generateJavaSource("                        " + methodName + ".invoke(" + targetName + ", new Object[]{(" + methodName + ".getParameterTypes()[0]).cast(" + resultName + ")});");
            ctxt.generateJavaSource("                    }else{");
            ctxt.generateJavaSource("                        " + methodName + ".invoke(" + targetName + ", new Object[]{null});");
            ctxt.generateJavaSource("                    }");
            ctxt.generateJavaSource("                    " + successFlagName + " = true;");
            ctxt.generateJavaSource("                }");
            ctxt.generateJavaSource("            }");
            ctxt.generateJavaSource("            if(!" + successFlagName + "){");
            ctxt.generateJavaSource("                throw new JspException(\"Invalid property in <set>:\"+" + propertyName + ");");
            ctxt.generateJavaSource("            }");
            ctxt.generateJavaSource("        }");
            
            //catch the el exception and throw it as a JspException
            ctxt.generateJavaSource("        catch (IllegalAccessException ex) {");
            ctxt.generateJavaSource("            throw new JspException(ex);");
            ctxt.generateJavaSource("        } catch (java.beans.IntrospectionException ex) {");
            ctxt.generateJavaSource("            throw new JspException(ex);");
            ctxt.generateJavaSource("        } catch (java.lang.reflect.InvocationTargetException ex) {");
            ctxt.generateJavaSource("            throw new JspException(ex);");
            ctxt.generateJavaSource("        }");
            ctxt.generateJavaSource("    }");
            ctxt.generateJavaSource("}else{");
            ctxt.generateJavaSource("    throw new JspException();");
            ctxt.generateJavaSource("}");
        }
    }
    
}

Other Tomcat examples (source code examples)

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