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Java注解

 

 

 

 

 

 

 

 

 

 

 

 

前面都是抄的别人的，发点自己的东西

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package 注解.反射读取;
 
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
 
@Target(value = ElementType.TYPE)//修饰类
@Retention(value = RetentionPolicy.RUNTIME)
public @interface SxtTable
{
        String value();
}

　　

package 注解. 反射读取;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


//用来说明 SXtStudent 里面的属性特性

@Target(value = ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface SxtFiled
{
String columnName();
String type();
int length();
}

package 注解. 反射读取;

@SxtTable("tb_table")


public class SxtStudent
{
@SxtFiled(columnName = "id",type="int",length = 10)
private int id;
//对属性做了说明，

@SxtFiled(columnName = "sname",type="varchar",length = 10)
private  String StudentName;


@SxtFiled(columnName </span>= "age",type="int",length = 3<span style="color: rgba(0, 0, 0, 1)">)
</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)"> age;

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)"> getId()
{
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> setId(<span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)"> id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getStudentName() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> StudentName;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setStudentName(String studentName) {
    StudentName </span>=<span style="color: rgba(0, 0, 0, 1)"> studentName;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)"> getAge() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> age;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> setAge(<span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)"> age) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.age =<span style="color: rgba(0, 0, 0, 1)"> age;
}



}

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package 注解.反射读取;
 
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
 
//反射读取ANN
public class DEMO
{
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException
    {
      Class Clazz= Class.forName("注解.反射读取.SxtStudent");//包含对应类的全部信息 包含注解
 
//        Annotation annot[]=Clazz.getAnnotations();//获取注解
//        for(Annotation a:annot)
//        {
//            System.out.println(a);
//        }
 
         
        //直接获得特定的注解
//        SxtTable st= (SxtTable) Clazz.getAnnotation(SxtTable.class);
//        System.out.println(st);
 
 
        //获得对应类的属性的注解
        Field f=Clazz.getDeclaredField("StudentName");
        System.out.println(f);
        SxtFiled sxtf=f.getAnnotation(SxtFiled.class);
        System.out.println(sxtf);
        System.out.println(sxtf.columnName());
        System.out.println(sxtf.length());
        System.out.println(sxtf.type());
    }
}