Struts example source code file (JSONWriter.java)

This example Struts source code file (JSONWriter.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 - Struts tags/keywords

bean, class, collection, enum, exception, javabean, jsonannotationfinder, jsonexception, jsonexception, method, method, object, object, reflection, regex, stack, string, string, text, util

The Struts JSONWriter.java source code

/*
 * $Id: JSONWriter.java 1079368 2011-03-08 14:24:16Z mcucchiara $
 *
 * 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.struts2.json;

import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import org.apache.struts2.json.annotations.JSON;
import org.apache.struts2.json.annotations.JSONFieldBridge;
import org.apache.struts2.json.annotations.JSONParameter;
import org.apache.struts2.json.bridge.FieldBridge;
import org.apache.struts2.json.bridge.ParameterizedBridge;

import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.text.CharacterIterator;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.StringCharacterIterator;
import java.util.*;
import java.util.regex.Pattern;

/**
 * <p>
 * Serializes an object into JavaScript Object Notation (JSON). If cyclic
 * references are detected they will be nulled out.
 * </p>
 */
class JSONWriter {
    private static final Logger LOG = LoggerFactory.getLogger(JSONWriter.class);

    /**
     * By default, enums are serialzied as name=value pairs
     */
    public static final boolean ENUM_AS_BEAN_DEFAULT = false;

    static char[] hex = "0123456789ABCDEF".toCharArray();
    private StringBuilder buf = new StringBuilder();
    private Stack stack = new Stack();
    private boolean ignoreHierarchy = true;
    private Object root;
    private boolean buildExpr = true;
    private String exprStack = "";
    private Collection<Pattern> excludeProperties;
    private Collection<Pattern> includeProperties;
    private DateFormat formatter;
    private boolean enumAsBean = ENUM_AS_BEAN_DEFAULT;
    private boolean excludeNullProperties;

    /**
     * @param object Object to be serialized into JSON
     * @return JSON string for object
     * @throws JSONException
     */
    public String write(Object object) throws JSONException {
        return this.write(object, null, null, false);
    }

    /**
     * @param object Object to be serialized into JSON
     * @return JSON string for object
     * @throws JSONException
     */
    public String write(Object object, Collection<Pattern> excludeProperties,
                        Collection<Pattern> includeProperties, boolean excludeNullProperties) throws JSONException {
        this.excludeNullProperties = excludeNullProperties;
        this.buf.setLength(0);
        this.root = object;
        this.exprStack = "";
        this.buildExpr = ((excludeProperties != null) && !excludeProperties.isEmpty())
                || ((includeProperties != null) && !includeProperties.isEmpty());
        this.excludeProperties = excludeProperties;
        this.includeProperties = includeProperties;
        this.value(object, null);

        return this.buf.toString();
    }

    /**
     * Detect cyclic references
     */
    private void value(Object object, Method method) throws JSONException {
        if (object == null) {
            this.add("null");

            return;
        }

        if (this.stack.contains(object)) {
            Class clazz = object.getClass();

            // cyclic reference
            if (clazz.isPrimitive() || clazz.equals(String.class)) {
                this.process(object, method);
            } else {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Cyclic reference detected on " + object);
                }

                this.add("null");
            }

            return;
        }

        this.process(object, method);
    }

    /**
     * Serialize object into json
     */
    private void process(Object object, Method method) throws JSONException {
        this.stack.push(object);

        if (object instanceof Class) {
            this.string(object);
        } else if (object instanceof Boolean) {
            this.bool((Boolean) object);
        } else if (object instanceof Number) {
            this.add(object);
        } else if (object instanceof String) {
            this.string(object);
        } else if (object instanceof Character) {
            this.string(object);
        } else if (object instanceof Map) {
            this.map((Map) object, method);
        } else if (object.getClass().isArray()) {
            this.array(object, method);
        } else if (object instanceof Iterable) {
            this.array(((Iterable) object).iterator(), method);
        } else if (object instanceof Date) {
            this.date((Date) object, method);
        } else if (object instanceof Calendar) {
            this.date(((Calendar) object).getTime(), method);
        } else if (object instanceof Locale) {
            this.string(object);
        } else if (object instanceof Enum) {
            this.enumeration((Enum) object);
        } else {
            this.bean(object);
        }

        this.stack.pop();
    }

    /**
     * Instrospect bean and serialize its properties
     */
    private void bean(Object object) throws JSONException {
        this.add("{");

        BeanInfo info;

        try {
            Class clazz = object.getClass();

            info = ((object == this.root) && this.ignoreHierarchy) ? Introspector.getBeanInfo(clazz, clazz
                    .getSuperclass()) : Introspector.getBeanInfo(clazz);

            PropertyDescriptor[] props = info.getPropertyDescriptors();

            boolean hasData = false;
            for (PropertyDescriptor prop : props) {
                String name = prop.getName();
                Method accessor = prop.getReadMethod();
                Method baseAccessor = findBaseAccessor(clazz, accessor);

                if (baseAccessor != null) {
                    if (baseAccessor.isAnnotationPresent(JSON.class)) {
                        JSONAnnotationFinder jsonFinder = new JSONAnnotationFinder(baseAccessor).invoke();

                        if (!jsonFinder.shouldSerialize()) continue;
                        if (jsonFinder.getName() != null) {
                            name = jsonFinder.getName();
                        }
                    }
                    // ignore "class" and others
                    if (this.shouldExcludeProperty(prop)) {
                        continue;
                    }
                    String expr = null;
                    if (this.buildExpr) {
                        expr = this.expandExpr(name);
                        if (this.shouldExcludeProperty(expr)) {
                            continue;
                        }
                        expr = this.setExprStack(expr);
                    }

                    Object value = accessor.invoke(object);
                    if (baseAccessor.isAnnotationPresent(JSONFieldBridge.class)) {
                        value = getBridgedValue(baseAccessor, value);
                    }

                    boolean propertyPrinted = this.add(name, value, accessor, hasData);
                    hasData = hasData || propertyPrinted;
                    if (this.buildExpr) {
                        this.setExprStack(expr);
                    }
                }
            }

            // special-case handling for an Enumeration - include the name() as
            // a property */
            if (object instanceof Enum) {
                Object value = ((Enum) object).name();
                this.add("_name", value, object.getClass().getMethod("name"), hasData);
            }
        } catch (Exception e) {
            throw new JSONException(e);
        }

        this.add("}");
    }

    private Object getBridgedValue(Method baseAccessor, Object value) throws InstantiationException, IllegalAccessException {
        JSONFieldBridge fieldBridgeAnn = baseAccessor.getAnnotation(JSONFieldBridge.class);
        if (fieldBridgeAnn != null) {
            Class impl = fieldBridgeAnn.impl();
            FieldBridge instance = (FieldBridge) impl.newInstance();

            if (fieldBridgeAnn.params().length > 0 && ParameterizedBridge.class.isAssignableFrom(impl)) {
                Map<String, String> params = new HashMap(fieldBridgeAnn.params().length);
                for (JSONParameter param : fieldBridgeAnn.params()) {
                    params.put(param.name(), param.value());
                }
                ((ParameterizedBridge) instance).setParameterValues(params);
            }
            value = instance.objectToString(value);
        }
        return value;
    }

    private Method findBaseAccessor(Class clazz, Method accessor) {
        Method baseAccessor = null;
        if (clazz.getName().indexOf("$$EnhancerByCGLIB$$") > -1) {
            try {
                baseAccessor = Class.forName(
                        clazz.getName().substring(0, clazz.getName().indexOf("$$"))).getMethod(
                        accessor.getName(), accessor.getParameterTypes());
            } catch (Exception ex) {
                LOG.debug(ex.getMessage(), ex);
            }
        } else if (clazz.getName().indexOf("$$_javassist") > -1) {
            try {
                baseAccessor = Class.forName(
                        clazz.getName().substring(0, clazz.getName().indexOf("_$$")))
                        .getMethod(accessor.getName(), accessor.getParameterTypes());
            } catch (Exception ex) {
                LOG.debug(ex.getMessage(), ex);
            }
        } else {
            return accessor;
        }
        return baseAccessor;
    }

    /**
     * Instrospect an Enum and serialize it as a name/value pair or as a bean
     * including all its own properties
     */
    private void enumeration(Enum enumeration) throws JSONException {
        if (enumAsBean) {
            this.bean(enumeration);
        } else {
            this.string(enumeration.name());
        }
    }

    private boolean shouldExcludeProperty(PropertyDescriptor prop) throws SecurityException,
            NoSuchFieldException {
        String name = prop.getName();

        return name.equals("class") || name.equals("declaringClass") || name.equals("cachedSuperClass")
                || name.equals("metaClass");

    }

    private String expandExpr(int i) {
        return this.exprStack + "[" + i + "]";
    }

    private String expandExpr(String property) {
        if (this.exprStack.length() == 0)
            return property;
        return this.exprStack + "." + property;
    }

    private String setExprStack(String expr) {
        String s = this.exprStack;
        this.exprStack = expr;
        return s;
    }

    private boolean shouldExcludeProperty(String expr) {
        if (this.excludeProperties != null) {
            for (Pattern pattern : this.excludeProperties) {
                if (pattern.matcher(expr).matches()) {
                    if (LOG.isDebugEnabled())
                        LOG.debug("Ignoring property because of exclude rule: " + expr);
                    return true;
                }
            }
        }

        if (this.includeProperties != null) {
            for (Pattern pattern : this.includeProperties) {
                if (pattern.matcher(expr).matches()) {
                    return false;
                }
            }

            if (LOG.isDebugEnabled())
                LOG.debug("Ignoring property because of include rule:  " + expr);
            return true;
        }

        return false;
    }

    /**
     * Add name/value pair to buffer
     */
    private boolean add(String name, Object value, Method method, boolean hasData) throws JSONException {
        if (!excludeNullProperties || (value != null)) {
            if (hasData) {
                this.add(',');
            }
            this.add('"');
            this.add(name);
            this.add("\":");
            this.value(value, method);
            return true;
        }

        return false;
    }

    /**
     * Add map to buffer
     */
    private void map(Map map, Method method) throws JSONException {
        this.add("{");

        Iterator it = map.entrySet().iterator();

        boolean warnedNonString = false; // one report per map
        boolean hasData = false;
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            Object key = entry.getKey();
            String expr = null;
            if (this.buildExpr) {
                if (key == null) {
                    LOG.error("Cannot build expression for null key in " + this.exprStack);
                    continue;
                } else {
                    expr = this.expandExpr(key.toString());
                    if (this.shouldExcludeProperty(expr)) {
                        continue;
                    }
                    expr = this.setExprStack(expr);
                }
            }
            if (hasData) {
                this.add(',');
            }
            hasData = true;
            if (!warnedNonString && !(key instanceof String)) {
                LOG.warn("JavaScript doesn't support non-String keys, using toString() on "
                        + key.getClass().getName());
                warnedNonString = true;
            }
            this.value(key.toString(), method);
            this.add(":");
            this.value(entry.getValue(), method);
            if (this.buildExpr) {
                this.setExprStack(expr);
            }
        }

        this.add("}");
    }

    /**
     * Add date to buffer
     */
    private void date(Date date, Method method) {
        JSON json = null;
        if (method != null)
            json = method.getAnnotation(JSON.class);
        if (this.formatter == null)
            this.formatter = new SimpleDateFormat(JSONUtil.RFC3339_FORMAT);

        DateFormat formatter = (json != null) && (json.format().length() > 0) ? new SimpleDateFormat(json
                .format()) : this.formatter;
        this.string(formatter.format(date));
    }

    /**
     * Add array to buffer
     */
    private void array(Iterator it, Method method) throws JSONException {
        this.add("[");

        boolean hasData = false;
        for (int i = 0; it.hasNext(); i++) {
            String expr = null;
            if (this.buildExpr) {
                expr = this.expandExpr(i);
                if (this.shouldExcludeProperty(expr)) {
                    it.next();
                    continue;
                }
                expr = this.setExprStack(expr);
            }
            if (hasData) {
                this.add(',');
            }
            hasData = true;
            this.value(it.next(), method);
            if (this.buildExpr) {
                this.setExprStack(expr);
            }
        }

        this.add("]");
    }

    /**
     * Add array to buffer
     */
    private void array(Object object, Method method) throws JSONException {
        this.add("[");

        int length = Array.getLength(object);

        boolean hasData = false;
        for (int i = 0; i < length; ++i) {
            String expr = null;
            if (this.buildExpr) {
                expr = this.expandExpr(i);
                if (this.shouldExcludeProperty(expr)) {
                    continue;
                }
                expr = this.setExprStack(expr);
            }
            if (hasData) {
                this.add(',');
            }
            hasData = true;
            this.value(Array.get(object, i), method);
            if (this.buildExpr) {
                this.setExprStack(expr);
            }
        }

        this.add("]");
    }

    /**
     * Add boolean to buffer
     */
    private void bool(boolean b) {
        this.add(b ? "true" : "false");
    }

    /**
     * escape characters
     */
    private void string(Object obj) {
        this.add('"');

        CharacterIterator it = new StringCharacterIterator(obj.toString());

        for (char c = it.first(); c != CharacterIterator.DONE; c = it.next()) {
            if (c == '"') {
                this.add("\\\"");
            } else if (c == '\\') {
                this.add("\\\\");
            } else if (c == '/') {
                this.add("\\/");
            } else if (c == '\b') {
                this.add("\\b");
            } else if (c == '\f') {
                this.add("\\f");
            } else if (c == '\n') {
                this.add("\\n");
            } else if (c == '\r') {
                this.add("\\r");
            } else if (c == '\t') {
                this.add("\\t");
            } else if (Character.isISOControl(c)) {
                this.unicode(c);
            } else {
                this.add(c);
            }
        }

        this.add('"');
    }

    /**
     * Add object to buffer
     */
    private void add(Object obj) {
        this.buf.append(obj);
    }

    /**
     * Add char to buffer
     */
    private void add(char c) {
        this.buf.append(c);
    }

    /**
     * Represent as unicode
     *
     * @param c character to be encoded
     */
    private void unicode(char c) {
        this.add("\\u");

        int n = c;

        for (int i = 0; i < 4; ++i) {
            int digit = (n & 0xf000) >> 12;

            this.add(hex[digit]);
            n <<= 4;
        }
    }

    public void setIgnoreHierarchy(boolean ignoreHierarchy) {
        this.ignoreHierarchy = ignoreHierarchy;
    }

    /**
     * If true, an Enum is serialized as a bean with a special property
     * _name=name() as all as all other properties defined within the enum.<br/>
     * If false, an Enum is serialized as a name=value pair (name=name())
     *
     * @param enumAsBean true to serialize an enum as a bean instead of as a name=value
     *                   pair (default=false)
     */
    public void setEnumAsBean(boolean enumAsBean) {
        this.enumAsBean = enumAsBean;
    }

    private static class JSONAnnotationFinder {
        private boolean serialize = true;
        private Method accessor;
        private String name;

        public JSONAnnotationFinder(Method accessor) {
            this.accessor = accessor;
        }

        boolean shouldSerialize() {
            return serialize;
        }

        public String getName() {
            return name;
        }


        public JSONAnnotationFinder invoke() {
            JSON json = accessor.getAnnotation(JSON.class);
            serialize = json.serialize();
            if (serialize && json.name().length() > 0) {
                name = json.name();
            }
            return this;
        }
    }
}