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。
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。
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; /** * * <p>Title: Customer</p> * <p>Description:客户信息实体 </p> */ 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; } }
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; /** * * <p>Title: IsRequired</p> * <p>Description: 字段是否必填 </p> */ @Retention(value = RetentionPolicy.RUNTIME) @Target(value = {ElementType.FIELD}) public @interface IsRequired { /** * * <p>Title: isRequired</p> * <p>Description:true:必填 false:非必填 </p> * @return */ boolean isRequired() default true; }
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; /** * * <p>Title: PoUtils</p> * <p>Description:Po操作工具类 </p> */ @SuppressWarnings("unused") public class PoUtils { /** * <p>Title: getProperties</p> * <p>Description: 获取javabean属性通用方法 </p> * @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; } /** * <p>Title: IsFieldBlank</p> * <p>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 </p> * @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; } }
封装了响应的成功失败以及一些信息
package com.dao.chu.po; /** * * <p>Title: RespBody</p> * <p>Description: 响应实体类</p> */ 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 + "]"; } }package com.dao.chu.po; /** * * <p>Title: IsRequiredTest</p> * <p>Description: 必填成员变量测试类</p> */ 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(); } } }
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
