JSONSerialiser.java

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package br.ufrgs.inf.prosoft.jsonserialiser;

import java.io.IOException;
import java.io.Writer;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 *
 * @author romulo
 */
public class JSONSerialiser {

    private final Collection<Object> visited;
    private final Writer writer;

    private JSONSerialiser(Writer writer) {
        this.visited = new ArrayList<>();
        this.writer = writer;
    }

    public static void serialise(Object bean, Writer writer, boolean cyclicFields) throws IOException {
        JSONSerialiser jsonSerialiser = new JSONSerialiser(writer);
        jsonSerialiser.serialiseBean(bean, cyclicFields);
    }

    public static void serialise(Object bean, Writer writer) throws IOException {
        serialise(bean, writer, true);
    }

    public static String serialise(Object bean, boolean cyclicFields) {
        StringBuilder stringBuilder = new StringBuilder();
        try {
            serialise(bean, new StringBuilderWriter(stringBuilder), cyclicFields);
        } catch (IOException ex) {
        }
        return stringBuilder.toString();
    }

    public static String serialise(Object bean) {
        return serialise(bean, true);
    }

    public static String serialiseCylicObject(Object bean) {
        return serialise(bean);
    }

    public static String serialiseAcylicObject(Object bean) {
        return serialise(bean, false);
    }

    public static void serialiseAcylicObject(Object bean, Writer writer) throws IOException {
        serialise(bean, writer, false);
    }

    private void resetCycleBreaker() {
        this.visited.clear();
    }

    private void serialiseBean(Object bean, boolean cyclicFields) throws IOException {
        if (bean == null) {
            this.writer.append("null");
            return;
        }
        Class<?> klass = bean.getClass();
        List<Field> fields = new ArrayList<>();
        fields = getAllFields(fields, klass);
        this.writer.append("{");
        for (Iterator<Field> it = fields.iterator(); it.hasNext();) {
            Field field = it.next();
            try {
                field.setAccessible(true);
                Object result = field.get(bean);
                if (result == null) {
                    continue;
                }
                if (!cyclicFields) {
                    resetCycleBreaker();
                }
                this.writer.append("\"").append(field.getName()).append("\"");
                this.writer.append(":");
                wrap(result);
            } catch (Exception ignore) {
                System.err.println("[JSONSerialiser] field exception: " + ignore);
                this.writer.append("\"").append("JSON-FIELD-EXCEPTION").append("\"");
            }
            if (it.hasNext()) {
                this.writer.append(",");
            }
        }
        this.writer.append("}");
    }

    private void serialiseBean(Object bean) throws IOException {
        serialiseBean(bean, true);
    }

    private List<Field> getAllFields(List<Field> fields, Class<?> type) {
        for (Field field : type.getDeclaredFields()) {
            if (!field.getName().startsWith("ajc$tjp_")) {
                fields.add(field);
            }
        }
        if (type.getSuperclass() != null) {
            getAllFields(fields, type.getSuperclass());
        }
        return fields;
    }

    private void wrap(Object object) throws IOException {
        try {
            if (object == null) {
                this.writer.append("null");
                return;
            }
            if (object instanceof Boolean) {
                this.writer.append("\"").append(String.valueOf(object)).append("\"");
                return;
            }
            if (object instanceof Character) {
                serialiseString(String.valueOf(object));
                return;
            }
            if (object instanceof String) {
                String string = (String) object;
                serialiseString(string);
                return;
            }
            if (object instanceof Number) {
                this.writer.append("\"").append(String.valueOf(object)).append("\"");
                return;
            }
            if (object instanceof Enum) {
                serialiseString(((Enum<?>) object).name());
                return;
            }
            if (object instanceof Collection) {
                Collection<?> collection = (Collection<?>) object;
                serialiseCollection(collection);
                return;
            }
            if (object.getClass().isArray()) {
                serialiseArray(object);
                return;
            }
            if (object instanceof Map) {
                Map<?, ?> map = (Map<?, ?>) object;
                serialiseMap(map);
                return;
            }
            if (object instanceof Date) {
                Date date = (Date) object;
                this.writer.append("\"").append(String.valueOf(date.getTime())).append("\"");
                return;
            }
            if (visited.stream().anyMatch((visited) -> (visited == object))) {
                try {
                    this.writer.append("\"").append(String.valueOf(object)).append("\"");
                } catch (Exception e) {
                    this.writer.append("\"").append(object.getClass().getName()).append("\"");
                } finally {
                    return;
                }
            }
            visited.add(object);
            serialiseBean(object);
        } catch (ConcurrentModificationException exception) {
            System.err.println("[JSONSerialiser] ConcurrentModificationException");
        } catch (Exception exception) {
            System.err.println("[JSONSerialiser] wrap exception: " + exception);
            exception.printStackTrace();
            this.writer.append("\"").append("JSON_SERIALISE_EXCEPTION").append("\"");
        }
    }

    private void serialiseMap(Map map) throws IOException {
        try {
            this.writer.append("{");
            for (Iterator<?> it = map.keySet().iterator(); it.hasNext();) {
                Object key = it.next();
                if (key == null || map.get(key) == null) {
                    continue;
                }
                if (!(key instanceof String)) {
                    this.writer.append("\"");
                    wrap(key);
                    this.writer.append("\"");
                } else {
                    wrap(key);
                }
                this.writer.append(":");
                wrap(map.get(key));
                if (it.hasNext()) {
                    this.writer.append(",");
                }
            }
        } catch (Exception ex) {
            System.err.println("[JSONSerialiser] map serialise exception: " + ex);
        } finally {
            this.writer.append("}");
        }
    }

    private void serialiseArray(Object array) throws IOException {
        this.writer.append("[");
        try {
            int length = Array.getLength(array);
            for (int i = 0; i < length;) {
                Object object = Array.get(array, i);
                wrap(object);
                if (++i < length) {
                    this.writer.append(",");
                }
            }
        } catch (Exception ex) {
            System.err.println("[JSONSerialiser] array serialise exception: " + ex);
        } finally {
            this.writer.append("]");
        }
    }

    private void serialiseCollection(Collection collection) throws IOException {
        try {
            this.writer.append("[");
            Iterator it = collection.iterator();
            while (it.hasNext()) {
                Object object = it.next();
                wrap(object);
                if (it.hasNext()) {
                    this.writer.append(",");
                }
            }
        } catch (Exception ex) {
            System.err.println("[JSONSerialiser] collection serialise exception: " + ex);
        } finally {
            this.writer.append("]");
        }
    }

    private void serialiseString(String string) throws IOException {
        if (string == null || string.isEmpty()) {
            this.writer.append("\"\"");
            return;
        }
        try {
            this.writer.append('"');

            char b;
            char c = 0;
            String hexadecimal;
            int i;
            int len = string.length();

            for (i = 0; i < len; i++) {
                b = c;
                c = string.charAt(i);
                switch (c) {
                    case '\\':
                    case '"':
                        this.writer.append('\\');
                        this.writer.append(c);
                        break;
                    case '/':
                        if (b == '<') {
                            this.writer.append('\\');
                        }
                        this.writer.append(c);
                        break;
                    case '\b':
                        this.writer.append("\\b");
                        break;
                    case '\t':
                        this.writer.append("\\t");
                        break;
                    case '\n':
                        this.writer.append("\\n");
                        break;
                    case '\f':
                        this.writer.append("\\f");
                        break;
                    case '\r':
                        this.writer.append("\\r");
                        break;
                    default:
                        if (c < ' ' || (c >= '\u0080' && c < '\u00a0')
                                || (c >= '\u2000' && c < '\u2100')) {
                            this.writer.append("\\u");
                            hexadecimal = Integer.toHexString(c);
                            this.writer.append("0000", 0, 4 - hexadecimal.length());
                            this.writer.append(hexadecimal);
                        } else {
                            this.writer.append(c);
                        }
                }
            }
        } catch (Exception ex) {
            System.err.println("[JSONSerialiser] string serialise exception: " + ex);
        } finally {
            this.writer.append('"');
        }
    }
}