反射操作注解获得注解信息
练习:ORM
代码练习
import java.lang.annotation.*;
import java.lang.reflect.Field;
//练习反射操作注解
public class Test12 {
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
Class c1 = Class.forName("com.lu.reflection.Student2");
//通过反射获得注解
Annotation[] annotations = c1.getAnnotations();
for (Annotation annotation : annotations) {
System.out.println(annotation);
}
//获得注解的value的值。
Tablelu tablelu = (Tablelu)c1.getAnnotation(Tablelu.class);
String value = tablelu.value();
System.out.println(value);
//获得类指定的注解
Field f = c1.getDeclaredField("name");
Fieldlu annotation = f.getAnnotation(Fieldlu.class);
System.out.println(annotation.columnName());
System.out.println(annotation.type());
System.out.println(annotation.length());
}
}
@Tablelu("db_student")
class Student2{
@Fieldlu(columnName = "db_id",type = "int",length = 10)
private int id;
@Fieldlu(columnName = "db_age",type = "int",length = 10)
private int age;
@Fieldlu(columnName = "db_name",type = "varchar",length = 3)
private String name;
public Student2() {
}
public Student2(int id, int age, String name) {
this.id = id;
this.age = age;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Student2{" +
"id=" + id +
", age=" + age +
", name='" + name + '\'' +
'}';
}
}
//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Tablelu{
String value();
}
//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Fieldlu{
String columnName();
String type();
int length();
}