本篇博客主要聊聊自定义注解在项目中的应用，自定义注解用来做系统监控日志，这个用法已经烂大街了，无法让面试官眼前一亮的感觉。

项目开发中数据字典使用场景非常多，使用数据字典有一点非常的不方便，那就是数据库中存放的是数字，而实际页面上展示的却是汉字；那么这也就造成了，每次做页面展示的时候都需要给数字进行转义，将其转义成汉字内容展示到页面，而转换的过程过于繁琐；

咱们的自定义注解可以完美的解决这一问题；

浏览器输入：http://localhost:8080/student/listPager 测试

最后浏览器访问的效果图

当然，也可以不走默认规则，xxx就是在类属性上的自定义注解的属性值

相关的pom依赖

 <dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.4</version>
</dependency>

逆向工程生成实体类、mapper.xml、mapper.java

实体类

package com.javaxl.model;

public class DataDict {
    private Integer id;

    private String datasource;

    private String description;

    public DataDict(Integer id, String datasource, String description) {
        this.id = id;
        this.datasource = datasource;
        this.description = description;
    }

    public DataDict() {
        super();
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDatasource() {
        return datasource;
    }

    public void setDatasource(String datasource) {
        this.datasource = datasource;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

package com.javaxl.model;

public class DataItem {
    private Integer id;

    private String datasource;

    private String code;

    private String val;

    public DataItem(Integer id, String datasource, String code, String val) {
        this.id = id;
        this.datasource = datasource;
        this.code = code;
        this.val = val;
    }

    public DataItem() {
        super();
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDatasource() {
        return datasource;
    }

    public void setDatasource(String datasource) {
        this.datasource = datasource;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getVal() {
        return val;
    }

    public void setVal(String val) {
        this.val = val;
    }
}

package com.javaxl.model;

import com.javaxl.annotation.Dict;

public class Student {
    private Integer id;

    private String name;

    @Dict(dicDataSource = "stu_Level")
    private Integer stulevel;

    @Dict(dicDataSource = "stu_English",dicText = "xxx")
    private Integer englishlevel;

    @Dict(dicDataSource = "stu_hobby")
    private String stuhobby;

    public Student(Integer id, String name, Integer stulevel, Integer englishlevel, String stuhobby) {
        this.id = id;
        this.name = name;
        this.stulevel = stulevel;
        this.englishlevel = englishlevel;
        this.stuhobby = stuhobby;
    }

    public Student() {
        super();
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getStulevel() {
        return stulevel;
    }

    public void setStulevel(Integer stulevel) {
        this.stulevel = stulevel;
    }

    public Integer getEnglishlevel() {
        return englishlevel;
    }

    public void setEnglishlevel(Integer englishlevel) {
        this.englishlevel = englishlevel;
    }

    public String getStuhobby() {
        return stuhobby;
    }

    public void setStuhobby(String stuhobby) {
        this.stuhobby = stuhobby;
    }
}

Mapper.java

package com.javaxl.mapper;

import com.javaxl.model.DataDict;

public interface DataDictMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(DataDict record);

    int insertSelective(DataDict record);

    DataDict selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(DataDict record);

    int updateByPrimaryKey(DataDict record);

}

package com.javaxl.mapper;

import com.javaxl.model.DataItem;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.ResponseBody;

@Repository
public interface DataItemMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(DataItem record);

    int insertSelective(DataItem record);

    DataItem selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(DataItem record);

    int updateByPrimaryKey(DataItem record);

    DataItem selectByDatasourceCode(DataItem dataItem);
}

package com.javaxl.mapper;

import com.javaxl.model.Student;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface StudentMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(Student record);

    int insertSelective(Student record);

    Student selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(Student record);

    int updateByPrimaryKey(Student record);

    List<Student> listPager(Student student);
}

Service层

package com.javaxl.service;

import com.javaxl.model.DataItem;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:56
 */
public interface DataItemService {
    DataItem selectByDatasourceKey(DataItem dataItem);

    String selectByDatasourceKey(String dataSource, String key);
}

package com.javaxl.service;

import com.javaxl.model.Student;
import com.javaxl.util.PageBean;

import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:51
 */
public interface StudentService {
    List<Student> listPager(Student student, PageBean pageBean);
}

package com.javaxl.service.impl;

import com.javaxl.mapper.DataItemMapper;
import com.javaxl.model.DataItem;
import com.javaxl.service.DataItemService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 21:01
 */
@Service
public class DataItemServiceImpl implements DataItemService {
    @Autowired
    private DataItemMapper dataItemMapper;
    @Override
    public DataItem selectByDatasourceKey(DataItem dataItem) {
        return dataItemMapper.selectByDatasourceCode(dataItem);
    }

    @Override
    public String selectByDatasourceKey(String dataSource, String key) {
        DataItem dataItem = new DataItem();
        dataItem.setDatasource(dataSource);
        dataItem.setCode(key);
        return dataItemMapper.selectByDatasourceCode(dataItem).getVal();
    }
}

package com.javaxl.service.impl;

import com.javaxl.mapper.StudentMapper;
import com.javaxl.model.Student;
import com.javaxl.service.StudentService;
import com.javaxl.util.PageBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:54
 */
@Service
public class StudentServiceImpl implements StudentService {
    @Autowired
    private StudentMapper studentMapper;
    @Override
    public List<Student> listPager(Student student, PageBean pageBean) {
        return studentMapper.listPager(student);
    }
}

重点代码来了

package com.javaxl.controller;

import com.javaxl.model.Student;
import com.javaxl.service.StudentService;
import com.javaxl.util.PageBean;
import com.javaxl.util.PageUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 21:06
 */
@Controller
@RequestMapping("/student")
public class StudentController {
    @Autowired
    private StudentService studentService;

    @ResponseBody
    @RequestMapping("/listPager")
    public PageUtils listPager(Student student, HttpServletRequest req){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(req);
        List<Student> list = this.studentService.listPager(student,pageBean);
        PageUtils pageUtils = new PageUtils(list,pageBean.getTotal());
        return pageUtils;
    }
}

DictAspect.java

package com.javaxl.aspect;

import com.alibaba.fastjson.JSONObject;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.javaxl.annotation.Dict;
import com.javaxl.service.DataItemService;
import com.javaxl.util.ObjConvertUtils;
import com.javaxl.util.PageUtils;
import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

import java.lang.reflect.Field;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:39
 */
@Aspect
@Component
@Slf4j
public class DictAspect {
    private static String DICT_TEXT_SUFFIX = "_dictText";

    @Autowired
    private DataItemService dataItemService;

    // 定义切点Pointcut 拦截所有对服务器的请求
    @Pointcut("execution( * com.javaxl.controller.*.*(..))")
    public void excudeService() {
    }

    /**
     * 这是触发 excudeService 的时候会执行的，在环绕通知中目标对象方法被调用后的结果进行再处理
     *
     * @param pjp
     * @return
     * @throws Throwable
     */
    @Around("excudeService()")
    public Object doAround(ProceedingJoinPoint pjp) throws Throwable {
        //这是定义开始事件
        long time1 = System.currentTimeMillis();
        //这是方法并获取返回结果
        Object result = pjp.proceed();
        //这是获取到 结束时间
        long time2 = System.currentTimeMillis();
        log.debug("获取JSON数据 耗时：" + (time2 - time1) + "ms");
        //解析开始时间
        long start = System.currentTimeMillis();
        //开始解析（翻译字段内部的值凡是打了 @Dict 这玩意的都会被翻译）
        this.parseDictText(result);
        //解析结束时间
        long end = System.currentTimeMillis();
        log.debug("解析注入JSON数据  耗时" + (end - start) + "ms");
        return result;
    }

    /**
     * 本方法针对返回对象为Result 的PageUtils的分页列表数据进行动态字典注入
     * 字典注入实现 通过对实体类添加注解@dict 来标识需要的字典内容,字典分为单字典dataSource即可
     * 示例为Student   
     *  字段为stu_sex 添加了注解@Dict(dicDataSource = "stu_sex") 会在字典服务立马查出来对应的text 然后在请求list的时候将这个字典text，已字段名称加_dictText形式返回到前端
     * 例输入当前返回值的就会多出一个stu_sex_dictText字段
     * {
     * stu_sex:1,
     * stu_sex_dictText:"男"
     * }
     * 前端直接取值sext_dictText在table里面无需再进行前端的字典转换了
     * customRender:function (text) {
     * if(text==1){
     * return "男";
     * }else if(text==2){
     * return "女";
     * }else{
     * return text;
     * }
     * }
     * 目前vue是这么进行字典渲染到table上的多了就很麻烦了 这个直接在服务端渲染完成前端可以直接用
     *
     * @param result
     */
    private void parseDictText(Object result) {
        if (result instanceof PageUtils) {
            List<JSONObject> items = new ArrayList<>();
            PageUtils pageUtils = (PageUtils) result;
            //循环查找出来的数据
            for (Object record : pageUtils.getData()) {
                ObjectMapper mapper = new ObjectMapper();
                String json = "{}";
                try {
                    //解决@JsonFormat注解解析不了的问题详见SysAnnouncement类的@JsonFormat
                    json = mapper.writeValueAsString(record);
                } catch (JsonProcessingException e) {
                    log.error("json解析失败" + e.getMessage(), e);
                }
                JSONObject item = JSONObject.parseObject(json);

                //update-begin--Author:scott -- Date:20190603 ----for：解决继承实体字段无法翻译问题------
                //for (Field field : record.getClass().getDeclaredFields()) {
                for (Field field : ObjConvertUtils.getAllFields(record)) {
                    //update-end--Author:scott  -- Date:20190603 ----for：解决继承实体字段无法翻译问题------
                    if (field.getAnnotation(Dict.class) != null) {
                        String datasource = field.getAnnotation(Dict.class).dicDataSource();
                        String text = field.getAnnotation(Dict.class).dicText();
                        //获取当前带翻译的值
                        String key = String.valueOf(item.get(field.getName()));
                        //翻译字典值对应的txt
                        String textValue = translateDictValue(datasource, key);
                        //  DICT_TEXT_SUFFIX的值为，是默认值：
                        // public static final String DICT_TEXT_SUFFIX = "_dictText";
                        log.debug(" 字典Val : " + textValue);
                        log.debug(" __翻译字典字段__ " + field.getName() + DICT_TEXT_SUFFIX + "： " + textValue);
                        //如果给了文本名
                        if (!StringUtils.isEmpty(text)) {
                            item.put(text, textValue);
                        } else {
                            //走默认策略
                            item.put(field.getName() + DICT_TEXT_SUFFIX, textValue);
                        }

                    }
                    //date类型默认转换string格式化日期
                    if (field.getType().getName().equals("java.util.Date") && field.getAnnotation(JsonFormat.class) == null && item.get(field.getName()) != null) {
                        SimpleDateFormat aDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                        item.put(field.getName(), aDate.format(new Date((Long) item.get(field.getName()))));
                    }
                }
                items.add(item);
            }
            pageUtils.setData(items);

        }
    }


    /**
     * 翻译字典文本
     *
     * @param datasource
     * @param key
     * @return
     */
    private String translateDictValue(String datasource, String key) {
        //如果key为空直接返回就好了
        if (ObjConvertUtils.isEmpty(key)) {
            return null;
        }
        StringBuffer textValue = new StringBuffer();
        //分割 key 值
        String[] keys = key.split(",");
        //循环 keys 中的所有值
        for (String k : keys) {
            String tmpValue = null;
            log.debug(" 字典 key : " + k);
            if (k.trim().length() == 0) {
                continue; //跳过循环
            }
            tmpValue = dataItemService.selectByDatasourceKey(datasource, k.trim());

            if (tmpValue != null) {
                if (!"".equals(textValue.toString())) {
                    textValue.append(",");
                }
                textValue.append(tmpValue);
            }
        }
        //返回翻译的值
        return textValue.toString();
    }
}

Dict.java

package com.javaxl.annotation;

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

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:37
 *
 * 专门用于数据字典中的数字转汉字的自定义注解
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Dict {

    /**
     * 方法描述:  数据dataSource
     * @return 返回类型： String
     */
    String dicDataSource();

    /**
     * 方法描述:  这是返回后Put到josn中的文本 key 值
     * @return 返回类型： String
     */
    String dicText() default "";
}

PageUtils.java

package com.javaxl.util;

import java.io.Serializable;
import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:36
 */
public class PageUtils implements Serializable {
    private static final long serialVersionUID = 1L;
    //这是总行数
    private long total;
    //这是保持查询出来的数据
    private List<?> data;

    /**
     *
     * @param list 保存数据
     * @param total 查到多行数据
     */
    public PageUtils(List<?> list, long total) {
        this.data = list;
        this.total = total;
    }

    public long getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }

    public List<?> getData() {
        return data;
    }

    public void setData(List<?> data) {
        this.data = data;
    }

    public static long getSerialVersionUID() {
        return serialVersionUID;
    }
}

ObjConvertUtils.java

package com.javaxl.util;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-24 20:37
 */
public class ObjConvertUtils {
    /**
     * 获取类的所有属性，包括父类
     *
     * @param object
     * @return
     */
    public static Field[] getAllFields(Object object) {
        Class<?> clazz = object.getClass();
        List<Field> fieldList = new ArrayList<>();
        while (clazz != null) {
            fieldList.addAll(new ArrayList<>(Arrays.asList(clazz.getDeclaredFields())));
            clazz = clazz.getSuperclass();
        }
        Field[] fields = new Field[fieldList.size()];
        fieldList.toArray(fields);
        return fields;
    }

    public static boolean isEmpty(Object object) {
        if (object == null) {
            return (true);
        }
        if ("".equals(object)) {
            return (true);
        }
        if ("null".equals(object)) {
            return (true);
        }
        return (false);
    }


}

友情提示：

真正的自定义注解去做数据字典的转义，应该在切面类引用缓存技术，比如redis；不然的话每次转义一个数字为汉字，还需要查询一次数据库，性能十分低下；

over......