Java常用代码

1、记录某个实体类（表）的变化

①两个实体类比较，记录前后的数据变化，精确到每列的值

 

②、

  1 package gwm.xtkf.tool;
  2 
  3 import java.lang.reflect.Field;
  4 import java.lang.reflect.Method;
  5 import java.text.SimpleDateFormat;
  6 import java.util.Date;
  7 import java.util.HashMap;
  8 import java.util.Locale;
  9 import java.util.Map;
 10 
 11 import xs.jszx.systemmanage.domain.Purpose;
 12 
 13 public class CompareClass {
 14     
 15     public static String compareClass(Object from, Object target, Map<String, String> describe) throws Exception{
 16         
 17         if (from.getClass() == target.getClass()){
 18             Class<? extends Object> c = target.getClass();
 19             Field field[] = c.getDeclaredFields();
 20             
 21             StringBuilder str = new StringBuilder();
 22             for (Field f: field){
 23                 String type = f.getGenericType().toString();    //获取属性的类型
 24                
 25                 if (describe.get(f.getName())!=null){
 26                     Object fv = invokeMethod(from, f.getName(), type);
 27                     Object tv = invokeMethod(target, f.getName(), type);
 28                     
 29                     if (fv!=null && tv!=null){
 30                         if (!fv.equals(tv)){
 31                             str.append(describe.get(f.getName()) + ":" + tv + "->" + fv + ";");
 32                         }
 33                     }
 34                     else if(fv==null && tv==null){}
 35                     else{
 36                         
 37                         if (fv!=null && fv.toString().trim().length()>0){
 38                             str.append(describe.get(f.getName()) + ":" + tv + "->" + fv + ";");
 39                         }
 40                         if (tv!=null && tv.toString().trim().length()>0){
 41                             str.append(describe.get(f.getName()) + ":" + tv + "->" + fv + ";");
 42                         }
 43                         
 44                     }    
 45                 }
 46                       
 47             }
 48             
 49             return str.toString();
 50         }
 51         else{
 52             return null;
 53         }
 54     }
 55     
 56     @SuppressWarnings("unchecked")
 57     private static Object invokeMethod(Object owner, String methodName, String type) throws Exception {
 58         @SuppressWarnings("rawtypes")
 59         Class ownerClass = owner.getClass();  
 60         methodName = methodName.substring(0, 1).toUpperCase()  
 61                 + methodName.substring(1);  
 62         Method method = null;  
 63         
 64         try {  
 65             method = ownerClass.getMethod("get" + methodName);  
 66         } catch (SecurityException e) {  
 67         } catch (NoSuchMethodException e) {  
 68             return null;  
 69         }  
 70         //如果type是类类型，则前面包含"class "，后面跟类名  
 71         //对日期类型进行转换
 72         if(type.equals("class java.util.Date")){   
 73             Date date = (Date) method.invoke(owner);
 74             if(date != null){
 75                 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd",Locale.US);  
 76                 return sdf.format(date); 
 77             }            
 78         }  
 79         return method.invoke(owner);
 80     }
 81     
 82     public static void main(String[] args){
 83         
 84         Purpose purpose1 = new Purpose();
 85         Purpose purpose2 = new Purpose();
 86         
 87         
 88         purpose1.setName("住宅");
 89         purpose2.setName("别墅");
 90         
 91         Map<String, String> map = new HashMap<String, String>();
 92         map.put("name", "名称");
 93         
 94         try {
 95             System.out.println(compareClass(purpose1, purpose2, map));
 96         } catch (Exception e) {
 97             // TODO Auto-generated catch block
 98             e.printStackTrace();
 99         }
100     }
101 }