Java注解应用,自定义注解映射实现方案说明.
插件结构如图:
注册模块定义了三个:用于实体与表映射的注解,用于属性到表字段的映射,用于映射时过滤掉的注解.
1.用于实体与表映射的注解
package com.dobby.plugins.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* User: 苏若年
* Date: 14-10-9
* Time: 下午21:12
* Description:
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface GeneratorTable {
//标注映射时的表名
public String name() default "";
}
2.用于属性与字段映射的注解
package com.dobby.plugins.annotation;
import java.lang.annotation.*;
/**
* User: 苏若年
* Date: 14-10-9
* Time: 下午21:31
* Description:
*/
@Target({ElementType.METHOD,ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface GeneratorField {
/**
* 是否为主键
* @return
*/
boolean primaryKey() default false;
/**
* 映射的字段名
* @return
*/
public String name() default "";
}
3.用于废弃字段过滤的注解
package com.dobby.plugins.annotation;
import java.lang.annotation.*;
/**
* User: pudongping
* Date: 14-10-9
* Time: 下午21:15
* Description:
*/
@Target({ElementType.METHOD,ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface AbolishedField {
//标注映射时排除的字段
}
注解定义完成后,我们需要在扫描到的实体中根据注解映射规则进行扫描时自动封装
自动封装的核心业务逻辑如下
/**
* 根据对象构造,表映射
* @param object
* 实体对象
* @return
* 实体对象到字段表的映射,基于注解处理
*/
public static EntityTable constructEntityTableWithObject(Object object){
EntityTable entityTable = null;
try{
if(null == object){return null;}
ConcurrentMap<String,String> entityToTable = new ConcurrentHashMap<String, String>();
boolean isGeneratorTable = object.getClass().isAnnotationPresent(GeneratorTable.class);
System.out.println(object.getClass().getSimpleName());
if(isGeneratorTable){
GeneratorTable generatorTable = object.getClass().getAnnotation(GeneratorTable.class);
if(StringUtils.isBlank(generatorTable.name())){
entityToTable.put(object.getClass().getSimpleName(),firstLower(object.getClass().getSimpleName()));
}else{
entityToTable.put(object.getClass().getSimpleName(),generatorTable.name());
}
}else{
entityToTable.put(object.getClass().getSimpleName(),firstLower(object.getClass().getSimpleName()));
}
Field[] fields = object.getClass().getDeclaredFields();
if(null != fields){
entityTable = new EntityTable();
//主键组
ConcurrentMap<String,String> propertyToKey = new ConcurrentHashMap<String,String>();
//字段组
ConcurrentMap<String,String> propertyToColumn = new ConcurrentHashMap<String, String>();
//主键到集合类型映射
ConcurrentMap<String,Object> propertyPKeyType = new ConcurrentHashMap<String,Object>();
for (int i = 0; i < fields.length; i++) {
//判断是否剔除
boolean isAbolishedField = fields[i].isAnnotationPresent(AbolishedField.class);
if(isAbolishedField){
//跳过该字段的提取
continue;
}
//判断是否是主键
boolean isGeneratorField = fields[i].isAnnotationPresent(GeneratorField.class);
if(isGeneratorField){
// 取注解中的文字说明
GeneratorField generatorField = fields[i].getAnnotation(GeneratorField.class);
boolean primaryKey = generatorField.primaryKey();
if(primaryKey){
//添加到主键集合
propertyPKeyType.put(fields[i].getName(),fields[i].getType().getName());
propertyToKey.put(fields[i].getName(),generatorField.name());
}else{
if(StringUtils.isBlank(generatorField.name())){
propertyToColumn.put(fields[i].getName(),fields[i].getName());
}else{
propertyToColumn.put(fields[i].getName(),generatorField.name());
}
}
continue;
}
propertyToColumn.put(fields[i].getName(), fields[i].getName());
}
entityTable.setPropertyPKeyType(propertyPKeyType);
entityTable.setPropertyToPKey(propertyToKey);
entityTable.setPropertyToColumn(propertyToColumn);
}
entityTable.setEntityToTable(entityToTable);
}catch (Exception e){
e.printStackTrace();
}
return entityTable;
}
EntityTable时实体与表结构映射的一个简易对象.
如下,我们定义的实体
package com.dobby.code.make.model;
import com.dobby.plugins.annotation.AbolishedField;
import com.dobby.plugins.annotation.GeneratorField;
import com.dobby.plugins.annotation.GeneratorTable;
import java.io.Serializable;
/**
* Created by 苏若念 on 2014/11/26.
*/
//映射表别名
@GeneratorTable(name = "tb_member")
public class Member implements Serializable {
//映射该字段,并且为主键,自定义字段别名
@GeneratorField(primaryKey = true, name = "m_Id")
private Integer id;
@GeneratorField(name = "member_name")
private String memberName;
//映射时不映射该字段
@AbolishedField
private String address;
//不使用注解,默认为使用属性名进行映射
private String zipCode;
//getter and setter
}
查看实体映射过程
EntityTable entityTable = BeanUtils.constructEntityTableWithPath("com.dobby.code.make.model.Member");
System.out.println("主键映射" + entityTable.getPropertyToPKey());
System.out.println("字段映射" + entityTable.getPropertyToColumn());
System.out.println("主键集合" + entityTable.getPropertyPKeyType());
System.out.println("表名映射" + entityTable.getEntityToTable());
通过注解映射后的结果如下:
主键映射{id=m_Id}
字段映射{zipCode=zipCode, memberName=member_name}
主键集合{id=java.lang.Integer}
表名映射{Member=tb_member}
因为我们使用了注解映射过滤,所以address字段映射时被排斥.
转载请注明出处:[http://www.cnblogs.com/dennisit/p/4125103.html]
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