这里有新鲜出炉的 Java 并发编程示例,程序狗速度看过来!
Java 程序设计语言
java 是一种可以撰写跨平台应用软件的面向对象的程序设计语言,是由 Sun Microsystems 公司于 1995 年 5 月推出的 Java 程序设计语言和 Java 平台(即 JavaEE(j2ee), JavaME(j2me), JavaSE(j2se))的总称.
本篇文章主要介绍了 java 反射和自定义注解的综合应用,小编觉得挺不错的,现在分享给大家,也给大家做个参考.一起跟随小编过来看看吧
前言
前几天学习了反射和自定义注解,刚好工作中遇到一个小问题:前台传递到后台的必填字段为空,导致不能插入数据库.就是这样一个小问题,让我考虑到是否可以做一个通用的方法,让前台传递过来的必填字段在后台也校验一遍,如果传递为空,则把响应字段返回提示.因此,我考虑的是用注解的方式,在必填字段上面定义,利用反射得到必填字段的字段名,判断是否为空,并返回响应的信息.
需求模拟
假设客户有:姓名,年龄,地址,手机号码,身份证号等信息,而我们是做金融业务,所以关键是看客户的三要素:姓名,身份证号,手机号码.我们要保证前台传递过来的这三个值不为空.
废话不多说,直接上代码.只看红框里面的即可.
目录结构
客户信息类:Customer
这个是个实体类,我们在:姓名,身份证号码,手机号码上都用了我们的自定义注解.
package com.dao.chu.po;
/**
*
*
Title: Customer
*
Description:客户信息实体
*/
public class Customer {
private int id;@IsRequired private String name; // 姓名
@IsRequired private String idnum; // 身份证号码
@IsRequired private String phone; // 手机号
private String sex; // 性别
private int age; // 年龄
private String address; // 地址
@Override public String toString() {
return "Customer [id=" + id + ", name=" + name + ", idnum=" + idnum + ", phone=" + phone + ", sex=" + sex + ", age=" + age + ", address=" + address + "]";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getIdnum() {
return idnum;
}
public void setIdnum(String idnum) {
this.idnum = idnum;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
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;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
自定义注解类:IsRequired
package com.dao.chu.po;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
*
*
Title: IsRequired
*
Description: 字段是否必填
*/
@Retention(value = RetentionPolicy.RUNTIME)@Target(value = {
ElementType.FIELD
}) public@interface IsRequired {
/**
*
*
Title: isRequired
*
Description:true:必填 false:非必填
* @return
*/
boolean isRequired()
default true;
}
关键工具类:PoUtils
我们在这个类里面主要用了反射的知识,得到带有自定义注解的字段,并取得这个对象的值进行判断
package com.dao.chu.po;
import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import javax.jws.webResult;
import com.sun.xml.internal.ws.util.StringUtils;
/**
*
*
Title: PoUtils
*
Description:Po操作工具类
*/
@SuppressWarnings("unused") public class PoUtils {
/**
*
Title: getProperties
*
Description: 获取javabean属性通用方法
* @param t
* @param beanName
* @return
* @throws IllegalAccessException
* @throws IllegalArgumentException
* @throws InvocationTargetException
* @throws IntrospectionException
*/
private static < T > Object getProperties(T t, String beanName) throws IllegalAccessException,
IllegalArgumentException,
InvocationTargetException,
IntrospectionException {
Object nameValue = new PropertyDescriptor(beanName, t.getClass()).getReadMethod().invoke(t);
return nameValue;
}
/**
*
Title: IsFieldBlank
*
Description:判断前台传过来的必填字段是否为空 ,不正确则将相应字段返回
* @param t
* @return
* @throws IllegalAccessException
* @throws IllegalArgumentException
* @throws InvocationTargetException
* @throws IntrospectionException
*/
public static < T > RespBody IsFieldBlank(T t) throws IllegalAccessException,
IllegalArgumentException,
InvocationTargetException,
IntrospectionException {
RespBody respBody = new RespBody();
StringBuffer sb = new StringBuffer();
Field[] declaredFields = t.getClass().getDeclaredFields();
for (Field field: declaredFields) {
field.setAccessible(true);
String name = field.getName();
boolean fieldHasAnno = field.isAnnotationPresent(IsRequired.class);
if (fieldHasAnno) {
IsRequired annotation = field.getAnnotation(IsRequired.class);
boolean required = annotation.isRequired();
if (required) {
Object value = getProperties(t, name);
if (null == value) {
sb.append(name + ",");
}
}
}
}
if (null == sb.toString() || "".equals(sb.toString())) {
respBody.isSuccess();
}
respBody.setSuccess(false);
respBody.setMsg(sb.toString().substring(0, sb.toString().lastIndexOf(",")) + " is required");
return respBody;
}
}
RespBody:响应实体类
封装了响应的成功失败以及一些信息
package com.dao.chu.po;
/**
*
*
Title: RespBody
*
Description: 响应实体类
*/
public class RespBody
{
private boolean isSuccess = true;
private String msg;
private Object data;
public boolean isSuccess()
{
return isSuccess;
}
public void setSuccess(boolean isSuccess)
{
this.isSuccess = isSuccess;
}
public String getMsg()
{
return msg;
}
public void setMsg(String msg)
{
this.msg = msg;
}
public Object getData()
{
return data;
}
public void setData(Object data)
{
this.data = data;
}
public RespBody(boolean isSuccess, String msg, Object data)
{
super();
this.isSuccess = isSuccess;
this.msg = msg;
this.data = data;
}
public RespBody(boolean isSuccess, String msg)
{
super();
this.isSuccess = isSuccess;
this.msg = msg;
}
public RespBody()
{
}
@Override
public String toString()
{
return "ReturnBody [isSuccess=" + isSuccess + ", msg=" + msg + ", data=" + data + "]";
}
}
测试类:IsRequiredTest
package com.dao.chu.po;
/**
*
*
Title: IsRequiredTest
*
Description: 必填成员变量测试类
*/
public class IsRequiredTest {
public static void main(String[] args) {
Customer customer = new Customer();
try {
//=========第一次不赋值==========
RespBody respBody = PoUtils.IsFieldBlank(customer);
//不通过则返回提示信息
if (!respBody.isSuccess()) {
System.out.println("1." + respBody.getMsg());
}
//=========第二次给姓名赋值==========
customer.setName("张三");
respBody = PoUtils.IsFieldBlank(customer);
//不通过则返回提示信息
if (!respBody.isSuccess()) {
System.out.println("2." + respBody.getMsg());
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
输出结果
第一次三个值都为空,提示三个都是必填的,第二次因为姓名赋值了,所以提示另外两个是必填的,本次实验宣告结束,本人知识有限,若有更好的方法欢迎指正
来源: http://www.phperz.com/article/18/0119/354287.html