2. java 反射机制构建JSON字符串

jdbc获取list转为json。


import java.lang.reflect.Field; 
import java.lang.reflect.InvocationTargetException; 
import java.lang.reflect.Method; 
import java.util.ArrayList; 
import java.util.List; 
 
import com.test.hzw.bean.test_user; 
import com.test.hzw.dao.impl.DaoImpl; 
 
/**
* Json转换测试类
* @author star
*
*/ 
@SuppressWarnings({"unchecked","unused"}) 
public class Reflect004 { 
 
    /**
     * @param args
     * @throws Exception 
     */ 
    public static void main(String[] args) throws Exception { 
        DaoImpl dao = new DaoImpl(); 
        test_user u = new test_user(); 
        String sqlPage = "SELECT * FROM user WHERE id <= "; 
        sqlPage += " (SELECT id FROM user ORDER BY id LIMIT "+(2-1)*20+", 1) "; 
        sqlPage += " ORDER BY id LIMIT 20 " ;   
        /*
         * 从数据库查询并获得集合
         * 
         * PS: 该方法是上一篇文章的内容
         */ 
        List<test_user> listT = (List<test_user>)dao.findList(u, sqlPage, new ArrayList()); 
        String s = ToJsonByList(listT); 
        System.out.println(s);   
        System.out.println(ToJsonByAll(listT.get(0)).toString()); 
    }  
     
    /**
     * 根据List集合生成Json数组格式字符串(只支持bean方式)
     * @param <T>
     * @param list 集合对象
     * @return  star
     */ 
    public static <T> String ToJsonByList(List<T> list){ 
        StringBuffer b = new StringBuffer("["); 
        if(list!=null&&list.size()>0){ 
            for (int i = 0; i < list.size(); i++){ 
                Object o = list.get(i); 
                try { 
                    //调用ToJsonByBean方法 
                    StringBuffer s = ToJsonByBean(o); 
                    if(s!=null&&!s.equals("")){ 
                        b.append(s).append(",");  
                    } 
                } catch (Exception e) {      
                    e.printStackTrace(); 
                }  
            }    
        } 
        b.append("]"); 
        return b.replace(b.lastIndexOf(","),b.lastIndexOf(",") + 1 ,"").toString(); 
    } 
     
    /** 
     * 根据javaBean生成Json对象格式字符串 
     * @param object 任意javaBean类型对象 
     * @return 拼接好的StringBuffer对象 
     */   
    public static StringBuffer ToJsonByBean(Object object) throws Exception{   
        Class clazz = object.getClass();  //获得Class对象 
        Field[] fields = clazz.getDeclaredFields();  //获得Class对象的字段数组 
        StringBuffer sb = new StringBuffer("{");  
        /*
         * 循环字段数组
         */ 
        for (Field field : fields) {     
            String fieldName = field.getName(); //获得字段名称    
            //获得字段对应的get方法对象 
            Method method = clazz.getMethod("get" + change(fieldName), null);   
            //调用get方法获得字段的值 
            Object property = method.invoke(object, null);   
             
            /*
             * 生成json字符串数据
             */ 
            if(property == null){   
                sb.append("\""+fieldName+"\":\"\",");     
            }else{ 
                if (field.getType().getName().equals("java.lang.Boolean")) 
                    sb.append("\""+fieldName+"\":"+Boolean.valueOf(property.toString())+",");    
                else 
                    sb.append("\""+fieldName+"\":\""+property+"\",");  
            }   
        }              
        sb.append("}");           
        return sb.replace(sb.lastIndexOf(","),sb.lastIndexOf(",") + 1 ,"");   
    }   
       
    /** 
     * @param src 源字符串 
     * @return 字符串，将src的第一个字母转换为大写，src为空时返回null 
     */   
    public static String change(String src) {   
        if (src != null) {   
            StringBuffer sb = new StringBuffer(src);   
            sb.setCharAt(0, Character.toUpperCase(sb.charAt(0)));   
            return sb.toString();   
        } else {   
            return null;   
        }   
    }   
     
    /** 
     * 生成Json数组格式字符串 
     * @param object 任意类型对象 
     * @return 拼接好的StringBuffer对象 
     */   
    public static StringBuffer ToJsonByAll(Object object) throws Exception{   
        Class clazz = object.getClass();   
        Field[] fields = clazz.getDeclaredFields();   
        StringBuffer sb = new StringBuffer("{[");   
        for (Field field : fields) {   
            String fieldName = field.getName();   
            Method method = clazz.getMethod("get" + change(fieldName), null);   
            Object property = method.invoke(object, null);   
            if(property == null){     
                sb.append("\"\",");   
            }else{   
                sb.append("\"" + property + "\",");   
            }   
        }          
        sb.append("]}");           
        return sb.replace(sb.lastIndexOf(","),sb.lastIndexOf(",") + 1 ,"");   
    } 
     
 
}