bean通过反射重写toString

Posted 2021-03-05 redqueen

思路1：

网上一大把，通过this.getClass().getDeclaredFields();获得所有属性，禁掉访问限制，最终输出属性值

// public String toString2() {
//     System.out.println("enter sourceObj toString...");
//
//     StringBuffer sb = new StringBuffer();
//     Field[] fields = this.getClass().getDeclaredFields();
//     for(Field iField : fields) {
//         iField.setAccessible(true);
//         sb.append(iField.getName());
//         sb.append("=");
//         try {
//             sb.append(iField.get(this));
//         }catch(IllegalArgumentException e) {
//             e.printStackTrace();
//         }catch(IllegalAccessException e) {
//             e.printStackTrace();
//         }
//         sb.append("
");
//     }
//     return sb.toString();
// }

思路2：
bean自身有public的get set方法，找到对应方法，截取名字，通过Method.invoke方法得到当前属性值

public  String toString(){
    System.out.println("SourceObj toString1...");

    Class<?> clazz = this.getClass();
    StringBuffer res = new StringBuffer(clazz.getSuperclass().getName() + " 
");
    for (; clazz != Object.class; clazz = clazz.getSuperclass()) {
        // System.out.println(clazz.getName());
        Method[] methods = clazz.getDeclaredMethods();
        for (int i = 0; i < methods.length; i++) {
            Method tmp = methods[i];
            String mName = tmp.getName();
            if (mName.startsWith("get")) {
                String fName = mName.substring(3);
                res.append(fName + " = ");
                try {
                    Object o = tmp.invoke(this, null);
                    if (o == null) {
                        res.append(" null 
");
                        continue;
                    }
                    if (o instanceof Double) {
                        res.append("" + ((Double) o).doubleValue() + " 
");
                    } else if (o instanceof Float) {
                        res.append("" + ((Float) o).floatValue() + " 
");
                    } else if (o instanceof Long) {
                        res.append("" + ((Long) o).longValue() + " 
");
                    } else if (o instanceof String) {
                        res.append("" + (String) o + " 
");
                    } else if (o instanceof Date) {
                        res.append("" + ((Date) o).toString() + " 
");
                    } else {
                        res.append("" + o.toString() + " 
");
                    }
                } catch (IllegalAccessException e) {
                    continue;
                } catch (InvocationTargetException ex) {
                    continue;
                }
            }
        }
    }
    return res.toString();
}

由于调用关系，需要注意getClass()获得的对象，this初始指向并不是bean本身。

 

bean：

public class SourceObj extends BaseObj{

    private String context;
    private String memo;
    private String source;

    public String getContext() { return context; }
    public void setContext(String context) { this.context = context; }
    public String getMemo() { return memo; }
    public void setMemo(String memo) { this.memo = memo; }
    public String getSource() { return source; }
    public void setSource(String source) { this.source = source; }
    
    public  String toString(){...}
}