java 注解和反射_Java注解和反射练习
直接上代码了！
package com.merryyou.annotation;
import java.lang.annotation.*;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface Key {
}
package com.merryyou.annotation;
import java.lang.annotation.*;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface notRecord {
}
package com.merryyou.annotation;
import java.lang.annotation.*;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface Table {
String name();
}
package com.merryyou.annotation;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
public class NumException extends Exception {
private String name;
public NumException(String message) {
this.name = message;
}
public NumException(Throwable cause, String name) {
super(name, cause);
this.name = name;
}
public String toString(){
return name;
}
}
package com.merryyou.annotation;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
@Table(name = "student")
public class Student {
@Key
private String id;
private String name;
@notRecord
private String sex;
private int age;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
package com.merryyou.annotation;
import java.lang.reflect.Field;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
public class Processing {
public String save(Object cl) throws IllegalArgumentException , IllegalAccessException ,NumException{
String sql="insert into ";
if(cl!=null){
Field[] fiels=cl.getClass().getDeclaredFields();//获得反射对象集合 返回 Field 对象的一个数组，这些对象反映此 Class 对象所表示的类或接口所声明的所有字段。
boolean t=cl.getClass().isAnnotationPresent(Table.class);//获得类是否有注解 如果指定类型的注释存在于此元素上，则返回 true，否则返回 false。
if(t){
Table tab=cl.getClass().getAnnotation(Table.class);// 如果存在该元素的指定类型的注释，则返回这些注释，否则返回 null。
sql+=tab.name();//获得表名
String name ="";//记录字段名
String value ="";//记录值名称
boolean bl=false;//记录主键是否为空
for(Field fl:fiels){//循环组装
fl.setAccessible(true);//开启支持私有变量的访问权限
Object tobj=fl.get(cl);//返回指定对象上此 Field 表示的字段的值。
if(tobj!=null){
if(fl.isAnnotationPresent(Key.class)){//判断是否存在主键
bl=true;
}
if(!fl.isAnnotationPresent(notRecord.class)){
name+=fl.getName()+",";
value+="'"+tobj.toString()+"',";
}
}
}
if(bl){
if(name.length()>0)
name=name.substring(0,name.length()-1);
if(value.length()>0)
value=value.substring(0,value.length()-1);
sql+="("+name+") values("+value+")";
}else
throw new NumException("未找到类主键 主键不能为空");
}else
throw new NumException("传入对象不是实体类");
}else
throw new NumException("传入对象不能为空");//抛出异常
return sql;
}
}
package com.merryyou.annotation;
/**
* Created on 2016/10/31 0031.
*
* @author zlf
* @since 1.0
*/
public class ProcessingTest {
public static void main(String[] args) throws NumException, IllegalAccessException {
Student student = new Student();
student.setId("ccc");
student.setName("姓名");
student.setAge(18);
student.setSex("男");
System.out.println(new Processing().save(student));
}
}
输出结果：
insert into student(id,name,age) values('ccc','姓名','18')