JAVA对象转JSON格式的字符串

package info.moogens.mvc.tools.json;

import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * JSON操作类
 * 暂时仅仅支持将java对象转储成JSON格式的字符串
 *
 * 原来用的 Simple Json 中的JSONValue.toJSONString 不能渲染POJO对象, 无论是使用 元注释还是实现接口 * 或多或少的都存在移植依赖性的问题.
 * 而POLO对象会用在多个地方,诸如: 视图/数据库表映射[DAO]/服务层 等等
 *
 * 如果对象属于复合对象的话(非基本数据类型)可能存在效率问题,建议不使用多层次的POLO类
 *
 * @author KenXu
 *
 */
public final class JsonSpread {

    @SuppressWarnings("unchecked")
    public static String toJSONString(Object value) {
        if (value == null) return "null";

        if (value instanceof Number) return value.toString();
        if (value instanceof Boolean) return value.toString();

        if (value instanceof String)
            return "\"" + escape((String) value) + "\"";

        if (value instanceof Double) {
            if (((Double) value).isInfinite() || ((Double) value).isNaN())
                return "null";
            else
                return value.toString();
        }

        if (value instanceof Float) {
            if (((Float) value).isInfinite() || ((Float) value).isNaN())
                return "null";
            else
                return value.toString();
        }

        if (value instanceof Map) return map2Json((Map) value);

        if (value instanceof Collection) return coll2Json((Collection) value);

        if (value.getClass().isArray()) return array2Json(value);

        return pojo2Json(value);
    }

    static String array2Json(Object array) {
        if (null == array) return "null" ;
        StringBuffer sb = new StringBuffer();
        sb.append('[');

        // 此处减1是为了下面的 逗号 追加
        int len = Array.getLength(array) - 1;
        if (len > -1){
            int i ;
            for (i = 0; i < len; i++) {
                sb.append(toJSONString(Array.get(array, i))).append(", ");
            }
            sb.append(toJSONString(Array.get(array, i)));
        }

        sb.append(']');
        return sb.toString();
    }

    static String coll2Json(Collection coll) {
        if (null == coll) return "null" ;
        StringBuffer sb = new StringBuffer();
        sb.append('[');
        for (Iterator it = coll.iterator(); it.hasNext();) {
            sb.append(toJSONString(it.next()));
            if (it.hasNext())
                sb.append(", ");
        }
        sb.append(']');
        return sb.toString();
    };

    static String pojo2Json(Object obj) {
        Class type = obj.getClass();
        Field[] fields = type.getDeclaredFields();
        Map map = new HashMap();
        for (Field f : fields) {
            if (Modifier.isStatic(f.getModifiers()))
                continue;
            String name = f.getName();
            f.setAccessible(true);
            Object value = null;
            try {
                value = f.get(obj);
            } catch (Exception e) {
                value = null;
            }
            map.put(name, value);
        }
        type = null;fields = null;
        return map2Json(map);
    }

    @SuppressWarnings("unchecked")
    static String map2Json(Map map) {
        if (null == map) return "null" ;

        StringBuffer sb = new StringBuffer();
        sb.append('{');
        for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry=(Map.Entry)it.next();

            String key = (String)entry.getKey();
            if (null == key) continue ;

            sb.append('\"');
            escape(key,sb);
            sb.append('\"').append(':').append(toJSONString(entry.getValue()));

            if (it.hasNext())
                sb.append(", ");
        }
        sb.append('}');
        return sb.toString();
    };

    /**
     * Escape quotes, \, /, \r, \n, \b, \f, \t and other control characters (U+0000 through U+001F).
     * @param s
     * @return
     */
    public static String escape(String s){
        if(s==null)
            return null;
        StringBuffer sb = new StringBuffer();
        escape(s, sb);
        return sb.toString();
    }

    /**
     * @param s - Must not be null.
     * @param sb
     */
    static void escape(String s, StringBuffer sb) {
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            switch (ch) {
            case '"':
                sb.append("\\\"");
                break;
            case '\\':
                sb.append("\\\\");
                break;
            case '\b':
                sb.append("\\b");
                break;
            case '\f':
                sb.append("\\f");
                break;
            case '\n':
                sb.append("\\n");
                break;
            case '\r':
                sb.append("\\r");
                break;
            case '\t':
                sb.append("\\t");
                break;
            case '/':
                sb.append("\\/");
                break;
            default:
                // Reference:
                if ((ch >= '\u0000' && ch <= '\u001F')
                        || (ch >= '\u007F' && ch <= '\u009F')
                        || (ch >= '\u2000' && ch <= '\u20FF')) {
                    String ss = Integer.toHexString(ch);
                    sb.append("\\u");
                    for (int k = 0; k < 4 - ss.length(); k++) {
                        sb.append('0');
                    }
                    sb.append(ss.toUpperCase());
                } else {
                    sb.append(ch);
                }
            }
        }
    }

}

 

测试代码:

 

package info.moogens.mvc.tools.json;

public final class User {
    private String name ,id;
    private Address ress ;

    public User(){
        this.name = "色色";
        this.id = "123";
        this.ress = new Address();
        this.ress.setCity("北京");
        this.ress.setZip(10086);
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public Address getRess() {
        return ress;
    }
    public void setRess(Address ress) {
        this.ress = ress;
    }

}

class Address {
    private String city;
    private int zip ;
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public int getZip() {
        return zip;
    }
    public void setZip(int zip) {
        this.zip = zip;
    }

}

 

package info.moogens.mvc.tools.json;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import info.moogens.demo.pcmaster.Application;
import info.moogens.mvc.tools.Toolkit;
import info.moogens.mvc.web.UDI;

public class X {

    /**
     * @param args
     */
    public static void main(String[] args) {
//      System.out.println((String)null);
        System.out.println(Toolkit.toJson(UDI.parseUDIString("/book/show")));
        System.out.println(Toolkit.toJson(new Application()));
        System.out.println(Toolkit.toJson(new User()));
        List list = new ArrayList();
        list.add("abc我是");
        list.add(new Integer(123));
        list.add(new Double(222.123));
        list.add(new Boolean(true));
        list.add(null);
        Map map = new HashMap();
        map.put("name","fang");
        map.put("age",new Integer(27));
        map.put("is_developer",new Boolean(true));
        map.put("weight",new Double(60.21));
        map.put("user",new User());
        map.put("list",list);

        int[] array = new int[5];
        array[4] = 72 ;
        array[3] = 21 ;
        array[1] = 12 ;

        map.put("array",array);

        System.out.println(Toolkit.toJson(map));
    }

}

 

 

测试结果:

写道

 

{"namespace":"default", "action":"show", "controller":"Book"}
{}
{"ress":{"zip":10086, "city":"北京"}, "name":"色色", "id":"123"}
{"list":["abc我是", 123, 222.123, true, null], "user":{"ress":{"zip":10086, "city":"北京"}, "name":"色色", "id":"123"}, "age":27, "is_developer":true, "name":"fang", "weight":60.21, "array":[0, 12, 0, 21, 72]}