将Java对象映射为JSON的方法

/**  
 * JSON 构造器类，可以将Java对象映射为JSON对象  
 * @author yyl  
 * @datetime 2005-12-11  
 * @version 0.9  
 */  
public class JsonBuilder {   
  
    //排除的字段   
    private Set<String> excludeFields = new HashSet<String>();   
    private static final Object EMPTY_OBJECT_ARRAY[] = new Object[0];   
  
    public JsonBuilder() {   
        excludeFields.add("class");   
        excludeFields.add("declaringClass");   
        excludeFields.add("metaClass");   
    }   
  
    /**  
     * 转换成JSON时需要排除的字段  
     * @param excludes  
     */  
    public void setExcludeFields(String... excludes) {   
        for (String exclude : excludes) {   
            excludeFields.add(exclude);   
        }   
    }   
  
    /**  
     * 将Java对象转化为JSON对象  
     * @param obj java对象  
     * @return js对象  
     */  
    public String encode(Object object) {   
        return encodeBasic(object);   
    }   
  
    /**  
     * 将Java对象转化为JSON对象  
     * @param obj java对象  
     * @return js对象  
     */  
    private String encodeBasic(Object object) {   
        // basic   
        if (object == null) {   
            return encodeNULL();   
        } else if (object instanceof String) {   
            return encodeString((String) object);   
        } else if (object instanceof Boolean) {   
            return encodeBoolean((Boolean) object);   
        } else if (object instanceof Number) {   
            return encodeNumber((Number) object);   
        } else if (object instanceof Map) {   
            return encodeMap((Map) object);   
        } else if (object instanceof Iterable) {   
            return encodeIterable((Iterable) object);   
        } else if (object instanceof Object[]) {// object.getClass().isArray()   
            return encodeArray((Object[]) object);   
        } else if (object instanceof java.util.Date) {   
            return encodeDate((java.util.Date) object);   
        } else {   
            Class clazz = object.getClass();   
  
            if (clazz.isInterface()) {   
                return encodeEmpty();   
            }   
  
            if (clazz.isEnum()) {   
                return encodeEnum((java.lang.Enum) object);   
            } else {   
                return encodeAdapter(object);   
            }   
        }   
    }   
  
    /**  
     * 返回一个NULL对象  
     * @return javascript null对象  
     */  
    private String encodeNULL() {   
        return "null";   
    }   
  
    /**  
     * 将Java-String对象转化为JSON对象  
     * @param string 字符串对象  
     * @return javascript string对象  
     */  
    private String encodeString(String string) {   
        StringBuilder sbr = new StringBuilder(string.length() * 4);   
        sbr.append("'");   
        for (int i = 0, sz = string.length(); i < sz; i++) {   
            char ch = string.charAt(i);   
            // handle unicode   
            if (ch > 0xfff) {   
                sbr.append("\\u");   
                sbr.append(hex(ch));   
            } else if (ch > 0xff) {   
                sbr.append("\\u0");   
                sbr.append(hex(ch));   
            } else if (ch > 0x7f) {   
                sbr.append("\\u00");   
                sbr.append(hex(ch));   
            } else if (ch < 32) {   
                switch (ch) {   
                case '\b':   
                    sbr.append('\\');   
                    sbr.append('b');   
                    break;   
                case '\n':   
                    sbr.append('\\');   
                    sbr.append('n');   
                    break;   
                case '\t':   
                    sbr.append('\\');   
                    sbr.append('t');   
                    break;   
                case '\f':   
                    sbr.append('\\');   
                    sbr.append('f');   
                    break;   
                case '\r':   
                    sbr.append('\\');   
                    sbr.append('r');   
                    break;   
                default:   
                    if (ch > 0xf) {   
                        sbr.append("\\u00");   
                        sbr.append(hex(ch));   
                    } else {   
                        sbr.append("\\u000");   
                        sbr.append(hex(ch));   
                    }   
                    break;   
                }   
            } else {   
                // line.   
                switch (ch) {   
                case '\'':   
                    sbr.append('\\');   
                    sbr.append('\'');   
                    break;   
                case '"':   
                    sbr.append('\\');   
                    sbr.append('"');   
                    break;   
                case '\\':   
                    sbr.append('\\');   
                    sbr.append('\\');   
                    break;   
                default:   
                    sbr.append(ch);   
                    break;   
                }   
            }   
        }   
        sbr.append("'");   
        return sbr.toString();   
    }   
  
    private String hex(char ch) {   
        return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH);   
    }   
  
    /**  
     * 将Java-Boolean对象转化为JSON对象  
     * @param obj 字符串对象  
     * @return javascript Boolean对象  
     */  
    private String encodeBoolean(Boolean b) {   
        return b.toString();   
    }   
  
    /**  
     * 将Java-Number对象转化为JSON对象  
     * @param n 数字对象  
     * @return javascript Number对象  
     */  
    private String encodeNumber(Number n) {   
        return n.toString();   
    }   
  
    /**  
     * 将Java-Map对象转化为JSON对象  
     *   
     * @param map Map对象  
     * @return javascript Map对象(简单对象)  
     */  
    private String encodeMap(Map map) {   
        StringBuilder sbr = new StringBuilder();   
        sbr.append("{");   
        boolean isFirst = true;   
        for (java.util.Iterator it = map.entrySet().iterator(); it.hasNext();) {   
            if (isFirst) {   
                isFirst = false;   
            } else {   
                sbr.append(",");   
            }   
            Map.Entry entry = (Map.Entry) it.next();   
            sbr.append(encodeBasic(entry.getKey())).append(":").append(encodeBasic(entry.getValue()));   
        }   
        sbr.append("}");   
        return sbr.toString();   
    }   
  
    /**  
     * 将Java-Iterable对象转化为JSON对象  
     * @param iterable Iterable对象  
     * @return javascript Array对象  
     */  
    private String encodeIterable(java.lang.Iterable iterable) {   
        StringBuilder sbr = new StringBuilder();   
        sbr.append("[");   
        int index = 0;   
        for (java.util.Iterator it = iterable.iterator(); it.hasNext();) {   
            if ((index++) > 0) {   
                sbr.append(",");   
            }   
            sbr.append(encodeBasic(it.next()));   
        }   
        sbr.append("]");   
        return sbr.toString();   
    }   
  
    /**  
     * 将Java-数组对象转化为JSON对象  
     * @param obj 数组对象  
     * @return javascript Array对象  
     */  
    private String encodeArray(Object[] array) {   
        StringBuilder sbr = new StringBuilder();   
        sbr.append("[");   
        for (int index = 0; index < array.length; index++) {   
            if (index > 0) {   
                sbr.append(",");   
            }   
            Object o = array[index];   
            sbr.append(encodeBasic(o));   
        }   
        sbr.append("]");   
        return sbr.toString();   
    }   
  
    /**  
     * 将Java-Date对象转化为JSON对象  
     * @param date 日期对象  
     * @return javascript Date对象  
     */  
    private String encodeDate(java.util.Date date) {   
        return new StringBuilder().append("new Date(").append(date.getTime()).append(")").toString();   
    }   
  
    /**  
     * 将Java-Enum对象转化为JSON对象  
     * @param e 枚举对象  
     * @return javascript Date对象  
     */  
    private String encodeEnum(java.lang.Enum e) {   
        return "'" + e.name() + "'";   
    }   
  
    /**  
     * 返回一个JSON简单对象  
     * @return javascript 简单对象  
     */  
    private String encodeEmpty() {   
        return "{}";   
    }   
  
    /**  
     * 将Java对象转化为JSON对象  
     * @param object Java对象  
     * @return 如果适配器能解析,则返回解析后的JSON对象，否则返回一个默认Empty JSON对象  
     */  
    private String encodeAdapter(Object object) {   
        try {   
            Map<String, Object> proxy = new HashMap<String, Object>();   
            Class clazz = object.getClass();   
            if (clazz == null) {   
                throw new IllegalArgumentException("No bean class specified");   
            }   
            proxy.put("class", clazz.getName());   
            PropertyDescriptor[] descriptors = null;   
            try {   
                descriptors = Introspector.getBeanInfo(clazz).getPropertyDescriptors();   
            } catch (IntrospectionException e) {   
                descriptors = new PropertyDescriptor[0];   
            }   
            for (int i = 0, j = descriptors.length; i < j; i++) {   
                PropertyDescriptor descriptor = descriptors[i];   
                String key = descriptor.getName();   
                //排除的字段   
                if (excludeFields.contains(key)) {   
                    continue;   
                }   
                Method method = descriptor.getReadMethod();   
                if (descriptor.getReadMethod() != null) {   
                    Class<?> type = descriptor.getPropertyType();   
  
                    if (type.isEnum()) {   
                        continue;   
                    }   
                    Object value = method.invoke(object, EMPTY_OBJECT_ARRAY);   
                    proxy.put(key, value);   
                }   
            }   
            return encodeMap(proxy);   
        } catch (Exception ex) {   
            return encodeEmpty();   
        }   
    }   
}  

 

 

使用方法试例：

JsonBuilder jber = new JsonBuilder();

jber.setExcludeFields("class","className");//排除的Bean属性

String json = jber.encode(bean);

System.out.println(json);

思路跟flexjson 有点像

应该已经有Java <-> JSON的工具了吧？而且还能够处理comment之类的东西。

JsonObject我就觉得做得不错呀，只是一些特定格式的，需要自己定制转换器

直接使用gson就可以搞定对象和JSON的相互转换