文章目录
- 前言
- 正文
-
- 一、POM依赖
- 二、核心Java文件
-
- [2.1 自定义表头注解 ExcelColumnTitle](#2.1 自定义表头注解 ExcelColumnTitle)
- [2.2 自定义标题头的映射接口](#2.2 自定义标题头的映射接口)
- [2.3 自定义有序map存储表内数据](#2.3 自定义有序map存储表内数据)
- [2.4 表头工厂](#2.4 表头工厂)
- [2.5 表flag和表头映射枚举](#2.5 表flag和表头映射枚举)
- [2.6 测试用的实体](#2.6 测试用的实体)
-
- [2.6.1 NameAndFactoryDemo](#2.6.1 NameAndFactoryDemo)
- [2.6.2 StudentDemo](#2.6.2 StudentDemo)
- [2.7 启动类](#2.7 启动类)
- [2.8 测试控制器](#2.8 测试控制器)
- 三、测试
前言
日前，看到一个比较奇怪的导出功能。
需要根据不同的页面，以及指定不同的字段列表（任意顺序），然后导出对应的表格。
先假设一个场景：
假如你的系统有多个列表展示页，每页中可以依据筛选条件，调整展示的列的个数，顺序等。然后要求导出的时侯，导出一摸一样的格式。也就是"所见即所得"的表格。
那么基于以上场景，我们就来考虑下如何实现？
本文就是对以上场景功能的一个实现。目前仅支持单sheet，不支持数据聚合等。
正文
本文项目环境：
java 8，springboot2.2.0, easyexcel
一、POM依赖
xml
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.2.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.2</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.2.11</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>二、核心Java文件
此处粘贴全部的java文件
2.1 自定义表头注解 ExcelColumnTitle
java
package headbean;
import java.lang.annotation.*;
/**
* 列名标题注解，标注列的标题
*
* @author feng
*/
@Documented
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ExcelColumnTitle {
String value();
}2.2 自定义标题头的映射接口
此接口仅仅是用于规范实体，以及用于辅助实现导出功能。
java
package headbean;
/**
* excel头部映射接口，用于规范导出的实体类
*
* @author feng
*/
public interface ExcelHeadMapInterface {
}2.3 自定义有序map存储表内数据
这个是表格导出时，字段数量，顺序的关键。
java
package headbean;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
/**
* 表格数据专用的map，带顺序，而且初始化的时候，依据指定的表头变量字段名确定导出数据的顺序
*
* @author feng
*/
public class ExcelDataLinkedHashMap<V> extends LinkedHashMap<String, V> {
private static final long serialVersionUID = -8554095999151235982L;
/**
* 头部字段名缓存
*/
private final Set<String> headColumnNamesCache;
/**
* ExcelDataLinkedHashMap构造器
*
* @param headColumnNames 表头字段变量名，例如：[name,studentNo,age,className]
*/
public ExcelDataLinkedHashMap(List<String> headColumnNames) {
// 字段名去重
headColumnNames = headColumnNames.stream().distinct().collect(Collectors.toList());
// 构建字段名缓存
this.headColumnNamesCache = new HashSet<>(headColumnNames);
// 指定列数据排列顺序
for (String headColumnName : headColumnNames) {
this.put(headColumnName, null);
}
}
@Override
public V put(String key, V value) {
// 只保存字段名缓存中的key以及value
if (headColumnNamesCache.contains(key)) {
return super.put(key, value);
}
return null;
}
}2.4 表头工厂
负责实现初始化表头字段名，以及后期使用时，从中获取表头信息。
核心功能是解析自定义的表头注解。
java
package factory;
import enums.ExcelHeadBeanFlagEnum;
import headbean.ExcelColumnTitle;
import headbean.ExcelHeadMapInterface;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
public class ExcelHeadMapFactory {
/**
* 全局表头名映射，ExcelHeadMapInterface实现类型为key，它内部变量的变量名和中文名映射为value
*/
private static final Map<Class<? extends ExcelHeadMapInterface>, Map<String, String>> HEAD_NAME_MAP = new HashMap<>();
public static void addHeadClass(Class<? extends ExcelHeadMapInterface> headClass) {
HEAD_NAME_MAP.put(headClass, mapToPrepareHead(headClass));
}
public static Map<String, String> getHeadMap(Class<? extends ExcelHeadMapInterface> headClass) {
return HEAD_NAME_MAP.get(headClass);
}
public static Map<String, String> getHeadMapByFlag(String flag) {
return getHeadMap(ExcelHeadBeanFlagEnum.getHeadClass(flag));
}
private static Map<String, String> mapToPrepareHead(Class<?> excelHeadClass) {
Map<String, String> namedMap = new HashMap<>();
Field[] declaredFields = excelHeadClass.getDeclaredFields();
for (Field declaredField : declaredFields) {
boolean annotationPresent = declaredField.isAnnotationPresent(ExcelColumnTitle.class);
if(annotationPresent) {
ExcelColumnTitle excelProperty = declaredField.getAnnotation(ExcelColumnTitle.class);
String chineseFieldName = excelProperty.value();
// 保存字段名和中文变量名
namedMap.put(declaredField.getName(), chineseFieldName);
}
}
return namedMap;
}
}2.5 表flag和表头映射枚举
这个枚举，如果你的系统这类功能很多。可以设计为数据库的方式做映射。然后以查字典表的方式，来处理。当然使用枚举大概率是够用了。
java
package enums;
import headbean.ExcelHeadMapInterface;
import headbean.NameAndFactoryDemo;
import headbean.StudentDemo;
import lombok.AllArgsConstructor;
import lombok.Getter;
import java.util.Arrays;
/**
* 表头flag枚举，映射flag与对应的实体类型；主要是可以根据flag找到对应实体类型。
*
* @author feng
*/
@Getter
@AllArgsConstructor
public enum ExcelHeadBeanFlagEnum {
NAME_AND_FACTORY_DEMO("NameAndFactoryDemo", NameAndFactoryDemo.class),
STUDENT_DEMO("StudentDemo", StudentDemo.class)
;
private final String flag;
private final Class<? extends ExcelHeadMapInterface> headClass;
public static Class<? extends ExcelHeadMapInterface> getHeadClass(String flag) {
return Arrays.stream(values()).
filter(bean -> bean.getFlag().equals(flag))
.findFirst()
.orElseThrow(RuntimeException::new)
.getHeadClass();
}
}2.6 测试用的实体
2.6.1 NameAndFactoryDemo
java
package headbean;
import lombok.Data;
@Data
public class NameAndFactoryDemo implements ExcelHeadMapInterface {
@ExcelColumnTitle("名字")
private String name;
@ExcelColumnTitle("工厂")
private String factory;
}2.6.2 StudentDemo
java
package headbean;
import lombok.Data;
@Data
public class StudentDemo implements ExcelHeadMapInterface {
@ExcelColumnTitle("姓名")
private String name;
@ExcelColumnTitle("年龄")
private Integer age;
@ExcelColumnTitle("学号")
private String studentNo;
@ExcelColumnTitle("班级")
private String className;
}2.7 启动类
主要是项目启动后，注册表头数据到内存。
java
package org.feng;
import factory.ExcelHeadMapFactory;
import headbean.ExcelHeadMapInterface;
import headbean.NameAndFactoryDemo;
import headbean.StudentDemo;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import java.util.ArrayList;
import java.util.List;
@SpringBootApplication
public class ExcelDemoApplication implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(ExcelDemoApplication.class, args);
}
@Override
public void run(String... args) throws Exception {
List<Class<? extends ExcelHeadMapInterface>> needRegisterExcelHeadClassList = new ArrayList<>();
needRegisterExcelHeadClassList.add(NameAndFactoryDemo.class);
needRegisterExcelHeadClassList.add(StudentDemo.class);
needRegisterExcelHeadClassList.forEach(ExcelHeadMapFactory::addHeadClass);
}
}2.8 测试控制器
java
package org.feng;
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.write.metadata.WriteSheet;
import enums.ExcelHeadBeanFlagEnum;
import factory.ExcelHeadMapFactory;
import headbean.ExcelDataLinkedHashMap;
import headbean.ExcelHeadMapInterface;
import headbean.NameAndFactoryDemo;
import headbean.StudentDemo;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import javax.annotation.PostConstruct;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.*;
import java.util.function.BiFunction;
@Controller
@RequestMapping("/excel")
public class ExcelDemoController {
@GetMapping("/exportDy")
public String exportDy(@RequestParam("flag")String flag,
@RequestParam("table")List<String> table, HttpServletResponse response) throws IOException {
String fileName = System.currentTimeMillis() + ".xlsx";
Class<? extends ExcelHeadMapInterface> headClass = ExcelHeadBeanFlagEnum.getHeadClass(flag);
Map<String, String> namedPrepareHeadMap = ExcelHeadMapFactory.getHeadMap(headClass);
Map<String, String> head = new LinkedHashMap<>();
for (String fieldName : table) {
head.put(namedPrepareHeadMap.get(fieldName), fieldName);
}
List<Map<String, String>> excelDataList = new ArrayList<>();
excelDataList.add(head);
// 制造假数据
for (BiFunction<Class<? extends ExcelHeadMapInterface>, List<Map<String, String>>, Boolean> biFunction : bizList) {
Boolean applied = biFunction.apply(headClass, excelDataList);
if(applied) {
break;
}
}
byte[] bytes = easyOut(excelDataList);
response.setHeader("Content-disposition", "attachment;filename=" + fileName);
response.setContentType("application/x-msdownload");
response.setCharacterEncoding("utf-8");
response.getOutputStream().write(bytes);
response.getOutputStream().flush();
return "success";
}
static final List<BiFunction<Class<? extends ExcelHeadMapInterface>, List<Map<String, String>>, Boolean>> bizList = new ArrayList<>();
@PostConstruct
private void init() {
bizList.add(this::genStudentDemoData);
bizList.add(this::genNameAndFactoryDemoData);
}
private boolean genStudentDemoData(Class<? extends ExcelHeadMapInterface> headClass, List<Map<String, String>> excelDataList) {
if(headClass == StudentDemo.class) {
Map<String, String> headMap = excelDataList.get(0);
for (int i = 0; i < 5; i++) {
Collection<String> fieldNames = headMap.values();
Map<String, String> data = new ExcelDataLinkedHashMap<>(new ArrayList<>(fieldNames));
excelDataList.add(data);
data.put("name", "张三"+(i+1));
data.put("age", "年龄"+(i+1));
data.put("studentNo", "学号"+(i+1));
data.put("className", "班级"+(i+1));
}
return true;
}
return false;
}
private boolean genNameAndFactoryDemoData(Class<? extends ExcelHeadMapInterface> headClass, List<Map<String, String>> excelDataList) {
if(headClass == NameAndFactoryDemo.class) {
Map<String, String> headMap = excelDataList.get(0);
for (int i = 0; i < 5; i++) {
Collection<String> fieldNames = headMap.values();
Map<String, String> data = new ExcelDataLinkedHashMap<>(new ArrayList<>(fieldNames));
excelDataList.add(data);
data.put("name", "张三"+(i+1));
data.put("factory", "工厂"+(i+1));
}
return true;
}
return false;
}
/**
* 导出数据（单sheet）
* @param exportData key 是sheet名称，value是每个sheet里面的数据，支持自定义表头
*/
public static byte[] easyOut(List<Map<String, String>> exportData) {
return easyOut(Collections.singletonMap("Sheet", exportData));
}
/**
* 导出数据（多sheet）
* @param exportData key 是sheet名称，value是每个sheet里面的数据，可以自定义
*/
public static byte[] easyOut(Map<String, List<Map<String, String>>> exportData) {
// 导出数据
ByteArrayOutputStream out = new ByteArrayOutputStream();
com.alibaba.excel.ExcelWriter excelWriter = EasyExcel.write(out).build();
int i=0;
for (Map.Entry<String, List<Map<String, String>>> entry: exportData.entrySet()) {
WriteSheet writeSheet = EasyExcel.writerSheet(i, entry.getKey()).head(head(entry.getValue().get(0))).build();
i++;
excelWriter.write(data(entry.getValue(), true), writeSheet);
}
excelWriter.finish();
return out.toByteArray();
}
private static List<List<String>> head(Map<String, String> cellData) {
List<List<String>> head = new ArrayList<>();
for (String key: cellData.keySet()) {
head.add(Collections.singletonList(key));
}
return head;
}
private static List<List<String>> data(List<Map<String, String>> sheetData, boolean skipHead) {
List<List<String>> data = new ArrayList<>();
for (int i = 0; i < sheetData.size(); i++) {
if(i == 0 && skipHead) {
continue;
}
data.add(new ArrayList<>(sheetData.get(i).values()));
}
return data;
}
}三、测试
测试1
http://localhost:8080/excel/exportDy?flag=StudentDemo\&table=name,studentNo,age,className
获得的表格内容为：
测试2
http://localhost:8080/excel/exportDy?flag=StudentDemo\&table=name,studentNo,age
获得的表格内容为：
测试3
http://localhost:8080/excel/exportDy?flag=NameAndFactoryDemo\&table=factory,name
获得的表格内容为：
测试4
http://localhost:8080/excel/exportDy?flag=StudentDemo\&table=className,name,studentNo
获得的表格内容为：
