注解_Annotation_内置注解_自定义注解_反射机制读取注解JAVA208-210

package com.test.annotation;

@MyAnnotation01
public class Demo01 {
@MyAnnotation01(age=19,studentName="test",id=1001,
schools={"北大","浙大"})
public static void main(String[] args) {
}

@MyAnnotation02(value="aaa")//或者("aaa")
public void test(){
}
}

package com.test.annotation;

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

@Target(value={ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation01 {

String studentName() default "";
int age() default 0;
int id() default -1;

String[] schools() default{"清华","复旦"};
}

package com.test.annotation;

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

@Target(value={ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation02 {
String value();
}

package com.test.annotation2;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;

/**
* 使用反射读取注解的信息，模拟处理注解信息的流程
*/
public class Demo {
public static void main(String[] args) {
try {
Class clazz = Class.forName("com.test.annotation2.SxtStudent");

//获取类的所有有效注解
Annotation[] annotations = clazz.getAnnotations();
for (Annotation a : annotations) {
System.out.println(a);
}
//获取类的指定的注解
SxtTable st = (SxtTable) clazz.getAnnotation(SxtTable.class);
System.out.println(st.value());

//获取类的属性的注解
Field f = clazz.getDeclaredField("sname");
SxtField sxtField = f.getAnnotation(SxtField.class);
System.out.println(sxtField.columnName()+"--"+sxtField.type()+"--"+sxtField.length());

//根据获取的表名和字段的信息，拼出DDL语句，然后，使用JDBC执行这个SQL，在数据库中生成相关的表

} catch (Exception e) {
e.printStackTrace();
}
}
}

package com.test.annotation2;

@SxtTable("tb_student")
public class SxtStudent {

@SxtField(columnName="id",type="int",length=10)
private int id;
@SxtField(columnName="sname",type="varchar",length=10)
private String sname;
@SxtField(columnName="age",type="int",length=3)
private int age;

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getStudentName() {
return sname;
}
public void setStudentName(String studentName) {
this.sname = studentName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}

package com.test.annotation2;

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

@Target(value={ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface SxtTable {
String value();
}

package com.test.annotation2;

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

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

@com.test.annotation2.SxtTable(value=tb_student)
tb_student
sname--varchar--10