将java种生成json

package utils;

import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 *
 * @author Administrator
 */
public class JSONUtil {

    /**
     * 字段过滤模式
     */
    public static final int INCLUDE = 0;
    public static final int REMOVE = 1;
    private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    /**
     *
     * @param <T>
     * @param o
     * @param maxLength 如果是String型，字符串的最大截取长度
     * @param createSub 如果是集合，那么集合中的子对象是否也生成json字串
     * @param Map<String, List<String&rt;&rt; filterMap :对指定的类进行字段的过滤
     * @param pattern 字段过滤模式：0(NOT)-只考虑已经列出的字段，1(REMOVE)-去除已经列出的字段
     * @return
     */
    public static <T> String toJSON(T o, int maxLength, boolean createSub, Map<String, String> filterMap, int pattern) {
        if (o == null) {
            return "null";
        }
        return toJSONx(o, o.getClass(), maxLength, createSub, filterMap, pattern, null);
    }

    public static <T> String toJSON(T o) {
        return JSONUtil.toJSON(o, 0, false, null, 0);
    }

    public static <T> String toJSON(T o, int maxLength) {
        return JSONUtil.toJSON(o, maxLength, false, null, 0);
    }

    /**
     *
     * @param <T>
     * @param o 要转为json的对象
     * @param clazz o的类型，关键时刻，用于强制转换o的类型T为V
     * @param maxLength
     * @param createSub
     * @param filterMap
     * @param pattern
     * @param olist 存储已经处理过的对象，在list中的索引越高，层级越深
     * @return
     */
    private static <T> String toJSONx(T o, Class clazz, int maxLength, boolean createSub, Map<String, String> filterMap, int pattern, List<Object> olist) {
        String s = "";
        String c = "";
        try {
            if (o != null) {
                /**
                 * 不知道是何种类型的，利用反射得到元素，但是防止循环引用，此处做一次检查，
                 * 有个缺陷，如果元素对相同对象引用两次，则只会自动转为不考虑下级对象模式，防止死循环
                 */
                olist = olist == null ? (new ArrayList<Object>()) : olist;
                for (Object vo : olist) {
                    if (vo == o) {
                        createSub = false;
                        S.p("-----(toJSONx)已爬取过,再爬取一次, 但不再考虑下级");
                        break;
                    } else {
                        olist.add(o);
                    }
                }

                c = o.getClass().getName();

                //检查各种类型情况
                if (String.class.getName().equals(c)) {
                    return S.addDoubleQuot(maxLength > 0 ? S.left(o + "", maxLength) : (o + ""));
                } else if (o instanceof Number
                        || Boolean.class.getName().equals(c)
                        || boolean.class.getName().equals(c)) {
                    return o + "";
                } else if (o instanceof Date) {
                    return S.addDoubleQuot(sdf.format((Date) o));
                } else if (o instanceof Collection) {
                    s += "[";
                    int k = 0;
                    for (Object oo : (Collection) o) {
                        if (createSub) {
                            if (k++ > 0) {
                                s += ", ";
                            }
                            s += toJSONx(oo, oo.getClass(), maxLength, createSub, filterMap, pattern, olist);
                        } else {
                            s += getJsonString(oo, maxLength);
                        }
                    }
                    s += "]";

                } else if (Map.class.getName().equals(c) || HashMap.class.getName().equals(c)) {
                    s += "{";
                    int k = 0;
                    Map map = (HashMap) o;
                    for (Object oo : map.keySet()) {
                        if (k++ > 0) {
                            s += ", ";
                        }
                        s += "\"" + S.inDoubleQuot(oo + "") + "\":";
                        if (map.get(oo) == null) {
                            s += "null";
                        } else {
                            if (createSub) {
                                s += toJSONx(map.get(oo), oo.getClass(), maxLength, createSub, filterMap, pattern, olist);
                            } else {
                                s += getJsonString(map.get(oo), maxLength);
                            }
                        }
                    }
                    s += "}";
                } else if (o != null && o.getClass().isArray()) {
                    s += "[";
                    for (int k = 0; k < Array.getLength(o); k++) {
                        if (createSub) {
                            if (k > 0) {
                                s += ", ";
                            }
                            s += toJSONx(Array.get(o, k), clazz, maxLength, createSub, filterMap, pattern, olist);
                        } else {
                            s += "getJsonString(Array.get(o, k), maxLength)";
                        }
                    }
                    s += "]";
                } else {
                    String[] fieldNames = null;
                    if (filterMap != null && filterMap.get(o.getClass().getName() + "") != null) {
                        fieldNames = S.xstring(filterMap.get(o.getClass().getName() + ""), "").split(",");
                        S.p("----o.getClass():" + o.getClass().getName() + "=" + filterMap.get(o.getClass().getName() + ""));
                    }
                    List<Field> flist = S.getAllFieldsIncludeSuper(clazz);
                    String get = "";
                    Method method;
                    Object oo = null;
                    if (flist.isEmpty()) {
                        s = "{}";
                    } else {
                        int k = 0;
                        s += "{";
                        for (Field f : flist) {
                            c = f.getType().getName();
                            //字段过滤
                            if (fieldNames != null) {
                                if (pattern == REMOVE && S.isInArray(f.getName(), fieldNames)) {//去除模式
                                    continue;
                                } else if (pattern == INCLUDE && !S.isInArray(f.getName(), fieldNames)) {//包含模式
                                    continue;
                                }
                            }

                            //看有没有get方法把值给取出来,无法取值的，跳过
                            get = S.markMethodString(f, "get");
                            if (S.hasMethod(o.getClass(), get)) {
                                method = o.getClass().getMethod(get);
                                oo = method.invoke(o);
                            } else {
                                continue;
                            }

                            if (k++ > 0) {
                                s += ", ";
                            }

                            s += S.addDoubleQuot(f.getName()) + " : ";
                            //如果抓取下级, 则递归抓取
                            if (createSub) {
                                s += toJSONx(oo, f.getType(), maxLength, createSub, filterMap, pattern, olist);
                            } else {
                                s += getJsonString(oo, maxLength);
                            }
                        }
                        s += "}";
                    }
                }

            } else {
                s += null;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return s;
    }

    public static String x(int c) {
        String s = "";
        while (c-- > 0) {
            s += "\t";
        }
        return s;
    }

    /**
     * 生成最大长度为maxLength的字符串，如果maxLength为0，则全部输出
     *
     * @param <T>
     * @param o
     * @param maxLength
     * @return
     */
    public static <T> String getJsonString(T o, int maxLength) {
        //检查各种类型情况
        String s = "", c = "";
        if (o == null) {
            return "null";
        } else if (o instanceof Number
                || Boolean.class.getName().equals((c = o.getClass().getName()))
                || boolean.class.getName().equals(c)) {
            s = o + "";
            s = maxLength > 0 ? S.left(s, maxLength) : s;
        } else if (String.class.getName().equals(c)) {
            s = o + "";
            s = S.addDoubleQuot(maxLength > 0 ? S.left(s, maxLength) : s);
        } else if (o instanceof Date) {
            s = sdf.format((Date) o);
            s = S.addDoubleQuot(maxLength > 0 ? S.left(s, maxLength) : s);
        } else if (o instanceof Collection || (o != null && o.getClass().isArray())) {
            s = "[]";
        } else if (Map.class.getName().equals(c) || HashMap.class.getName().equals(c)) {
            s = "{}";
        } else {
            s = S.addDoubleQuot("");
        }
        return s;
    }

    /**
     * 一个class是否实现了某个接口
     *
     * @param c
     * @param szInterface
     * @return
     */
    public static boolean isInterface(Class c, String szInterface) {
        Class[] face = c.getInterfaces();
        for (int i = 0, j = face.length; i < j; i++) {
            if (face[i].getName().equals(szInterface)) {
                return true;
            } else {
                Class[] face1 = face[i].getInterfaces();
                for (int x = 0; x < face1.length; x++) {
                    if (face1[x].getName().equals(szInterface)) {
                        return true;
                    } else if (isInterface(face1[x], szInterface)) {
                        return true;
                    }
                }
            }
        }
        if (null != c.getSuperclass()) {
            return isInterface(c.getSuperclass(), szInterface);
        }
        return false;
    }

    /**
     * 得到一个类中所有可用的Field的字符串List
     *
     * @param <T>
     * @param o
     * @return
     */
    public static <T> List<String> getFieldNameList(T o) {
        List<String> list = new ArrayList<String>();
        try {
            List<Field> flist = S.getAllFieldsIncludeSuper(((T) o).getClass());
            for (Field field : flist) {
                list.add(field.getName());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }

    /**
     * 向现有的json格式字串添加一个名称为key值为value的 key-value 对
     *
     * @param jsonString
     * @param key
     * @param jsonValue , 已经是json格式, 不要再添加引号了
     * @return
     */
    public static String push(String jsonString, String key, String jsonValue) {
        if (S.isEmpty(jsonString)
                || S.isEmpty(key)
                || S.isEmpty(jsonValue)
                || !jsonString.trim().endsWith("}")) {
            return jsonString;
        }
        jsonString = jsonString.trim();
        jsonString = jsonString.substring(0, jsonString.length() - 1)
                + (jsonString.indexOf(":") > 0 ? ", " : "")
                + S.addDoubleQuot(key) + ": "
                + jsonValue
                + "}";
        return jsonString;
    }

    public static void main(String[] args) {
        System.out.println(JSONUtil.toJSON(new Date()));
    }
}

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