通过反射的内省机制获取URL地址中出入的参数，并封装到对应的实体类中

标签：实体类 return String URL void 内省 private Integer public

本例需要添加的依赖：

<dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.7</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.28</version>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.2.8</version>
    </dependency>
    <!--mybatis分页插件-->
    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>5.3.1</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>2.0.12</version>
    </dependency>

GoodsInfo 实体类：

import java.util.Objects;

/**
 * GoodsInfo和GoodsType的映射关系
 * N        :  1
 *
 * 一个商品必定会对应一个商品分类
 */
public class GoodsInfo {
    private Integer goodsId;
    private String goodsName;
    private String goodsSerial;
    private String goodsImg;
    private Integer goodsSort;
    // 一级分类 在表中是一个外键
    private GoodsType parentType;
    // 二级分类 在表中是一个外键
    private GoodsType middleType;
    // 三级分类 在表中是一个外键
    private GoodsType subType;
    private Integer storeNumber;
    private Integer selledNumber;
    private Integer warnNumber;
    private Double marketPrice;
    private Double shopPrice;
    private Integer goodsEnable;
    private String summary;
    private Integer isnew;
    private Integer ishot;
    private Integer isrecommand;

    public Integer getGoodsId() {
        return goodsId;
    }

    public void setGoodsId(Integer goodsId) {
        this.goodsId = goodsId;
    }

    public String getGoodsName() {
        return goodsName;
    }

    public void setGoodsName(String goodsName) {
        this.goodsName = goodsName;
    }

    public String getGoodsSerial() {
        return goodsSerial;
    }

    public void setGoodsSerial(String goodsSerial) {
        this.goodsSerial = goodsSerial;
    }

    public String getGoodsImg() {
        return goodsImg;
    }

    public void setGoodsImg(String goodsImg) {
        this.goodsImg = goodsImg;
    }

    public Integer getGoodsSort() {
        return goodsSort;
    }

    public void setGoodsSort(Integer goodsSort) {
        this.goodsSort = goodsSort;
    }

    public GoodsType getParentType() {
        return parentType;
    }

    public void setParentType(GoodsType parentType) {
        this.parentType = parentType;
    }

    public GoodsType getMiddleType() {
        return middleType;
    }

    public void setMiddleType(GoodsType middleType) {
        this.middleType = middleType;
    }

    public GoodsType getSubType() {
        return subType;
    }

    public void setSubType(GoodsType subType) {
        this.subType = subType;
    }

    public Integer getStoreNumber() {
        return storeNumber;
    }

    public void setStoreNumber(Integer storeNumber) {
        this.storeNumber = storeNumber;
    }

    public Integer getSelledNumber() {
        return selledNumber;
    }

    public void setSelledNumber(Integer selledNumber) {
        this.selledNumber = selledNumber;
    }

    public Integer getWarnNumber() {
        return warnNumber;
    }

    public void setWarnNumber(Integer warnNumber) {
        this.warnNumber = warnNumber;
    }

    public Double getMarketPrice() {
        return marketPrice;
    }

    public void setMarketPrice(Double marketPrice) {
        this.marketPrice = marketPrice;
    }

    public Double getShopPrice() {
        return shopPrice;
    }

    public void setShopPrice(Double shopPrice) {
        this.shopPrice = shopPrice;
    }

    public Integer getGoodsEnable() {
        return goodsEnable;
    }

    public void setGoodsEnable(Integer goodsEnable) {
        this.goodsEnable = goodsEnable;
    }

    public String getSummary() {
        return summary;
    }

    public void setSummary(String summary) {
        this.summary = summary;
    }

    public Integer getIsnew() {
        return isnew;
    }

    public void setIsnew(Integer isnew) {
        this.isnew = isnew;
    }

    public Integer getIshot() {
        return ishot;
    }

    public void setIshot(Integer ishot) {
        this.ishot = ishot;
    }

    public Integer getIsrecommand() {
        return isrecommand;
    }

    public void setIsrecommand(Integer isrecommand) {
        this.isrecommand = isrecommand;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        GoodsInfo goodsInfo = (GoodsInfo) o;
        return Objects.equals(goodsId, goodsInfo.goodsId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(goodsId);
    }

    @Override
    public String toString() {
        return "GoodsInfo{" +
                "goodsId=" + goodsId +
                ", goodsName='" + goodsName + '\'' +
                ", goodsSerial='" + goodsSerial + '\'' +
                ", goodsImg='" + goodsImg + '\'' +
                ", goodsSort=" + goodsSort +
                ", parentType=" + parentType +
                ", middleType=" + middleType +
                ", subType=" + subType +
                ", storeNumber=" + storeNumber +
                ", selledNumber=" + selledNumber +
                ", warnNumber=" + warnNumber +
                ", marketPrice=" + marketPrice +
                ", shopPrice=" + shopPrice +
                ", goodsEnable=" + goodsEnable +
                ", summary='" + summary + '\'' +
                ", isnew=" + isnew +
                ", ishot=" + ishot +
                ", isrecommand=" + isrecommand +
                '}';
    }
}

GoodsType 实体类：

public class GoodsType {
    private Integer typeId; // 假设当前查询的商品分类的编号为1
    private String typeName;
    private String typeImg;
    private Integer sort;
    private Integer parentId;
    private String parentLevel;
    private Integer showNav;
    private Integer showIndex;
    private String icon;
    private String value2;
    private String value3;
    private List<GoodsInfo> goodsInfos;
    public GoodsType() {
    }

    public Integer getTypeId() {
        return typeId;
    }

    public void setTypeId(Integer typeId) {
        this.typeId = typeId;
    }

    public String getTypeName() {
        return typeName;
    }

    public void setTypeName(String typeName) {
        this.typeName = typeName;
    }

    public String getTypeImg() {
        return typeImg;
    }

    public void setTypeImg(String typeImg) {
        this.typeImg = typeImg;
    }

    public Integer getSort() {
        return sort;
    }

    public void setSort(Integer sort) {
        this.sort = sort;
    }

    public Integer getParentId() {
        return parentId;
    }

    public void setParentId(Integer parentId) {
        this.parentId = parentId;
    }

    public String getParentLevel() {
        return parentLevel;
    }

    public void setParentLevel(String parentLevel) {
        this.parentLevel = parentLevel;
    }

    public Integer getShowNav() {
        return showNav;
    }

    public void setShowNav(Integer showNav) {
        this.showNav = showNav;
    }

    public Integer getShowIndex() {
        return showIndex;
    }

    public void setShowIndex(Integer showIndex) {
        this.showIndex = showIndex;
    }

    public String getIcon() {
        return icon;
    }

    public void setIcon(String icon) {
        this.icon = icon;
    }

    public String getValue2() {
        return value2;
    }

    public void setValue2(String value2) {
        this.value2 = value2;
    }

    public String getValue3() {
        return value3;
    }

    public void setValue3(String value3) {
        this.value3 = value3;
    }

    public List<GoodsInfo> getGoodsInfos() {
        return goodsInfos;
    }

    public void setGoodsInfos(List<GoodsInfo> goodsInfos) {
        this.goodsInfos = goodsInfos;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        GoodsType goodsType = (GoodsType) o;
        return Objects.equals(typeId, goodsType.typeId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(typeId);
    }

    @Override
    public String toString() {
        return "GoodsType{" +
                "typeId=" + typeId +
                ", typeName='" + typeName + '\'' +
                ", typeImg='" + typeImg + '\'' +
                ", sort=" + sort +
                ", parentId=" + parentId +
                ", parentLevel='" + parentLevel + '\'' +
                ", showNav=" + showNav +
                ", showIndex=" + showIndex +
                ", icon='" + icon + '\'' +
                ", value2='" + value2 + '\'' +
                ", value3='" + value3 + '\'' +
                '}';
    }
}

查询参数对象：

/**
 * DTO: data transfer object ,  数据传输对象
 * 将来自于客户端查询参数封装到一个dto对象中，以供mybatis动态查询使用
 */
public class GoodsInfoDto extends PageDto{
    private Integer storeNumber;
    private Double marketPrice;
    private Integer selledNumber;

    public Integer getStoreNumber() {
        return storeNumber;
    }

    public void setStoreNumber(Integer storeNumber) {
        this.storeNumber = storeNumber;
    }

    public Double getMarketPrice() {
        return marketPrice;
    }

    public void setMarketPrice(Double marketPrice) {
        this.marketPrice = marketPrice;
    }

    public Integer getSelledNumber() {
        return selledNumber;
    }

    public void setSelledNumber(Integer selledNumber) {
        this.selledNumber = selledNumber;
    }

    @Override
    public String toString() {
        return "GoodsInfoDto{" +
                "pageNumber = " + super.getPageNum() +
                ",pageSize = " + super.getPageSize() +
                ",storeNumber=" + storeNumber +
                ", marketPrice=" + marketPrice +
                ", selledNumber=" + selledNumber +
                '}';
    }
}

继承自PageDto类：

public class PageDto {
    // 当前页码
    private Integer pageNum = 1;
    // 每页显示的条数
    private Integer pageSize = 5;

    public Integer getPageNum() {
        return pageNum;
    }

    public void setPageNum(Integer pageNum) {
        this.pageNum = pageNum;
    }

    public Integer getPageSize() {
        return pageSize;
    }

    public void setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
    }
}

servlet类：

@WebServlet("/goods")
public class GoodsInfoServlet extends HttpServlet{
    GoodsInfoService service = new GoodsInfoServiceImpl();
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //String name = Thread.currentThread().getName();
        //System.out.println("当前负责处理请求的线程为：" + name + ", 当前所访问的servlet对象为：" + this);
        //设置编码方式
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");

        ///////////////////////////第一种写法//////////////////////////////
        // 读取request请求中的参数，并封装到一个Map集合中
        //Map<String, String> map = RequestUtil.parameter2Map(req);
        // 利用反射和内省机制，将map集合中的键值映射为一个具体的GoodsInfoDto的对象
        //GoodsInfoDto goodsInfoDto = RequestUtil.convertMap2Object(GoodsInfoDto.class, map);

        /////////////////////////////第二种写法//////////////////////////////
        // 原始的写法，一次获取url参数中的所有参数
        /*String pageNumber = req.getParameter("pageNumber");
        String pageSize = req.getParameter("pageSize");
        String storeNumber = req.getParameter("storeNumber");
        String selledNumber = req.getParameter("selledNumber");
        String marketPrice = req.getParameter("marketPrice");

        // 手动实例化dto对象，并将参数转型赋值给dto
        GoodsInfoDto goodsInfoDto = new GoodsInfoDto();
        if (pageSize != null) {
            goodsInfoDto.setPageSize(Integer.valueOf(pageSize));
        }
        if (pageNumber != null) {
            goodsInfoDto.setPageNumber(Integer.valueOf(pageNumber));
        }
        if (storeNumber != null) {
            goodsInfoDto.setStoreNumber(Integer.valueOf(storeNumber));
        }
        if (selledNumber != null) {
            goodsInfoDto.setSelledNumber(Integer.valueOf(selledNumber));
        }
        if (marketPrice != null) {
            goodsInfoDto.setMarketPrice(Double.valueOf(marketPrice));
        }*/

        /////////////////////////第三种写法///////////////////////
        Map<String, String> map = RequestUtil.parameter2Map(req);
        // 将map集合转换为json字符串
        String jsonString = JSONObject.toJSONString(map);
        // 利用fastjson将json字符串还原为java对象
        GoodsInfoDto goodsInfoDto = JSONObject.parseObject(jsonString, GoodsInfoDto.class);

        System.out.println("goodsInfoDto=====" + goodsInfoDto);

        //调用业务逻辑层开始查询
        Result result = service.selectByCondition(goodsInfoDto);

        //将result对象转换为json字符串
        String json = JSONObject.toJSONString(result);

        // 告诉客户端，本次响应的结果为json字符串
        resp.setContentType("application/json");
        try (PrintWriter writer = resp.getWriter()) {
            // 将json响应给客户端
            writer.write(json);
            writer.flush();
        }
    }
}

RequestUtil类：

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.charset.StandardCharsets;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

public class RequestUtil {

    /**
     * 从request请求中，提取url参数，并封装到一个map集合中
     * @param request
     * @return
     */
    public static Map<String, String> parameter2Map(HttpServletRequest request) {
        Map<String, String> map = new HashMap<>();

        // 一个可迭代的枚举，每一个元素为url参数
        Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            // 获取所有的参数
            String parameter = parameterNames.nextElement();
            // 获取参数的值
            String value = request.getParameter(parameter);
            map.put(parameter, value);
        }

        return map;
    }

    /**
     * 将集合中的键值转换为泛型T的对象.
     * BUG:不能转换弗雷中的属性
     * @param tClass
     * @param map
     * @param <T>
     * @return
     */
    public static <T> T convertMap2Object(Class<T> tClass, Map<String, String> map) {
        try {
            // 实例化空对象
            T t = tClass.newInstance();
            Map<String, PropertyDescriptor> propertyDescriptorMap = new HashMap<>();
            try {
                // 得到tClass类对应类信息
                BeanInfo beanInfo = Introspector.getBeanInfo(tClass);
                // 得到tClass类的所有属性描述符，从而得到他们的set方法
                PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();

                //将属性描述符已属性名和PropertyDescriptor的映射到Map集合
                for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {
                    // 排除掉class
                    if (propertyDescriptor.getName().equals("class")) continue;
                    // 已属性名作为键，属性描述符作为值，保存到map集合
                    propertyDescriptorMap.put(propertyDescriptor.getName(), propertyDescriptor);
                }
            } catch (IntrospectionException e) {
                e.printStackTrace();
            }

            // 遍历map，将map中所有的键值映射为泛型T对象的属性上
            map.forEach((key,value) -> {
                try {
                    // 从属性映射中得到当前key键对应的属性
                    PropertyDescriptor propertyDescriptor = propertyDescriptorMap.get(key);
                    // 基于内省机制获取tClass对应的属性的封装方法
                    Method writeMethod = propertyDescriptor.getWriteMethod(); // setXxx封装方法
                    Class<?> type = propertyDescriptor.getPropertyType(); // 得到属性的类型
                    // 获取属性类型对应的转换器
                    Function<String, Object> function = Converters.lookup(type);
                    // 通过类型转换器，将字符串value转换为属性对应的类型
                    Object apply = function.apply(value);
                    //调用封装方法，为属性赋值
                    writeMethod.invoke(t, apply);
                }catch (InvocationTargetException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            });

            return t;
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        return null;
    }

    public static String extractJson(HttpServletRequest req) throws IOException {
        try (// 字节输入流
             ServletInputStream inputStream = req.getInputStream();
             // 将字节输入流转换为字符输入流
             InputStreamReader reader = new InputStreamReader(inputStream, StandardCharsets.UTF_8);
             // 缓冲流
             BufferedReader bufferedReader = new BufferedReader(reader)) {

            StringBuffer stringBuffer = new StringBuffer();
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                stringBuffer.append(line);
            }
            return stringBuffer.toString();
        }
    }
}

Converters类：

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

public class Converters {
    private static Map<Class<?>, Function<String,Object>> converts;

    static {
        // 将字符串转换为Integer的对象
        Function<String, Integer> integerFunction = (value) -> Integer.valueOf(value);
        // 将字符串转换为Double的对象
        Function<String, Double> doubleFunction = (value) -> Double.valueOf(value);

        // 将字符串转换为日期的对象
        Function<String, Date> dateFunction = (value) -> {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = null;
            try {
                date = format.parse(value);
            } catch (ParseException e) {
                e.printStackTrace();
            }
            return date;
        };

        // 提起注册了两个转换器
        converts = new HashMap(){{
            put(Integer.class,integerFunction);
            put(Double.class,doubleFunction);
            put(Date.class, dateFunction);
        }};
    }

    /**
     * 对外提供自定义注册转换的方法
     * @param aClass
     * @param function
     * @param <T>
     */
    public static <T> void register(Class<T> aClass, Function<String, Object> function) {
        converts.put(aClass, function);
    }

    public static Function<String, Object> lookup(Class<?> aClass) {
        if (!converts.containsKey(aClass)) {
            throw new RuntimeException("尚未注册" + aClass.getName() + "对应的转换器");
        }
        return converts.get(aClass);
    }
}

测试方法：

 @Test
    public void test3(){
        Map<String, String> map = new HashMap<String, String>(){{
            put("storeNumber", "100");
            put("marketPrice", "200");
            put("selledNumber", "20");
            put("pageNum", "5");
            put("pageSize", "10");
        }};

        GoodsInfoDto goodsInfoDto = RequestUtil.convertMap2Object(GoodsInfoDto.class, map);
        System.out.println(goodsInfoDto);
    }

测试效果图：

 

标签：实体类,return,String,URL,void,内省,private,Integer,public
From： https://www.cnblogs.com/huang2979127746/p/16772537.html