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java反射机制

2024-07-08 23:45:15   215人阅读

1.获取java entity里的属性有俩个方法：getDeclaredField()和getField();

　　getField() 只能获取public类型的属性；

　　getDeclaredField() 能获取类或接口声明的所有属性；

　如：

import java.lang.reflect.*;  public class HellWorld{    private double a;    public static final int b = 16;    String str = "helloword";     public static void main(String args[]) {       try {            Class cls = Class.forName("HellWorld");            Field fieldlist[] = cls.getDeclaredFields();            for (int i = 0; i < fieldlist.length; i++) {               Field fld = fieldlist[i];               System.out.println("name = " + fld.getName());  //获取属性名              System.out.println("decl class = " + fld.getDeclaringClass()); //所属的声明类              System.out.println("type = " + fld.getType());  //获取属性类型              int mod = fld.getModifiers();                System.out.println("modifiers = " + Modifier.toString(mod));  //属性成员的修饰语              System.out.println("///////////////");            }       }       catch (Throwable e) {            System.err.println(e);       }    } }

 输出：

 1     name = a 2     decl class = class HellWorld 3     type = double 4     modifiers = private 5     ///////////////// 6     name = b 7     decl class = class HellWorld 8     type = int 9     modifiers = public static final10     /////////////////11     name = str12     decl class = class HellWorld13     type = class java.lang.String14     modifiers = 15     /////////////////

使用场景：可以根据页面post/get过来的参数值，初始化java entity里的对应属性的值。

如：POST  a=2&str=test

 1 public void init(HttpServletRequest request){ 2         try { 3             String queryBody = IOUtils.toString(request.getInputStream()); 4              5             Class cls = Class.forName("HelloWorld"); 6              7             if(StringUtils.isNotBlank(queryBody)){ 8                 StringTokenizer st = new StringTokenizer(queryBody, "&"); 9                 10                 while (st.hasMoreTokens()) {11                     String pairs = st.nextToken();12                     String key = pairs.substring(0, pairs.indexOf(‘=‘));13                     String value = http://www.mamicode.com/pairs.substring(pairs.indexOf(‘=‘) + 1);14         15                     if(StringUtils.isBlank(value))16                         continue;17                     18                     value = http://www.mamicode.com/URLDecoder.decode(value,"UTF-8");19                     20                     Field fld = cls.getDeclaredField(key);21                     Class type = fld.getType();22                     if(type.toString().equalsIgnoreCase("double")){23                         fld.setDouble(this, Double.parseDouble(value));24                     }else{25                         fld.set(this, value);26                     }27                 }28             }29             30         } catch(UnsupportedEncodingException e){
31         } catch (IOException e) {
32         } catch (SecurityException e) {
33         } catch (NoSuchFieldException e) {
34         } catch (ClassNotFoundException e) {
35         } catch (IllegalArgumentException e) {
36         } catch (IllegalAccessException e) {
37         }38     }

 


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