1. 简介
Java解析、生成Excel比较有名的框架有Apache poi、jxl。但他们都存在一个严重的问题就是非常的耗内存，poi有一套SAX模式的API可以一定程度的解决一些内存溢出的问题，但POI还是有一些缺陷，比如07版Excel解压缩以及解压后存储都是在内存中完成的，内存消耗依然很大。easyexcel重写了poi对07版Excel的解析，能够原本一个3M的excel用POI sax依然需要100M左右内存降低到几M，并且再大的excel不会出现内存溢出，03版依赖POI的sax模式，在上层做了模型转换的封装，让使用者更加简单方便。
64M内存1分钟内读取75M(46W行25列)的Excel：
更多请参考：https://github.com/alibaba/easyexcel
2. 示例代码
- 创建工程
- 修改pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.c3stones</groupId>
<artifactId>spring-boot-easyexcel-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-easyexcel-demo</name>
<description>SpringBoot + Easyexcel Demo</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.8.RELEASE</version>
<relativePath />
</parent>
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.2.6</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
</project>
- 创建实体
import java.util.Date;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.write.style.ColumnWidth;
import com.alibaba.excel.annotation.write.style.ContentRowHeight;
import com.alibaba.excel.annotation.write.style.HeadRowHeight;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
/**
* 学生实体
*
* @author CL
*
*/
@Data
@NoArgsConstructor
@AllArgsConstructor
@HeadRowHeight(20)
@ColumnWidth(20)
@ContentRowHeight(15)
public class Student {
@ExcelProperty(index = 0, value = "学号")
private String sno;
@ExcelProperty(index = 1, value = "姓名")
private String name;
@ExcelProperty(index = 2, value = "年龄")
private Integer age;
@ExcelProperty(index = 3, value = "性别")
private String gender;
@ExcelProperty(index = 4, value = "籍贯")
private String nativePlace;
@ExcelProperty(index = 5, value = "入学时间")
private Date enrollmentTime;
}
- 创建文件读取类
该类需要继承抽象类AnalysisEventListener，但是不需要被Spring管理。
import java.util.ArrayList;
import java.util.List;
import com.alibaba.excel.context.AnalysisContext;
import com.alibaba.excel.event.AnalysisEventListener;
import com.c3stones.entity.Student;
import lombok.Getter;
/**
* 学生读取类
*
* @author CL
*
*/
public class StudentListener extends AnalysisEventListener<Student> {
@Getter
private List<Student> studentList = new ArrayList<Student>();
public StudentListener() {
super();
studentList.clear();
}
/**
* 每一条数据解析都会调用
*/
@Override
public void invoke(Student student, AnalysisContext context) {
studentList.add(student);
}
/**
* 所有数据解析完成都会调用
*/
@Override
public void doAfterAllAnalysed(AnalysisContext context) {
studentList.forEach(System.out::println);
}
}
- 创建文件导出导入Controller示例
import java.io.IOException;
import java.net.URLEncoder;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import com.alibaba.excel.EasyExcel;
import com.c3stones.entity.Student;
import com.c3stones.listener.StudentListener;
/**
* 学生Controller
*
* @author CL
*
*/
@RestController
@RequestMapping(value = "student")
public class StudentController {
/**
* 导出学生信息
*
* @param response
* @param request
* @throws IOException
* @throws ParseException
*/
@SuppressWarnings("serial")
@RequestMapping(value = "export")
public void exportStudentInfos(HttpServletResponse response, HttpServletRequest request)
throws IOException, ParseException {
// 设置响应类型
response.setContentType("application/vnd.ms-excel");
// 设置字符编码
response.setCharacterEncoding("utf-8");
// 设置响应头信息
response.setHeader("Content-disposition",
"attachment;filename*=utf-8\'\'" + URLEncoder.encode("学生花名册", "UTF-8") + ".xlsx");
List<Student> studentList = new ArrayList<Student>() {
{
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
add(new Student("1001", "张三", 23, "男", "陕西西安", dateFormat.parse("2020-09-01")));
add(new Student("1002", "李四", 22, "女", "陕西渭南", dateFormat.parse("2020-09-01")));
}
};
// 写入文件
EasyExcel.write(response.getOutputStream(), Student.class).sheet("学生信息").doWrite(studentList);
}
/**
* 导入学生信息
*
* @param file
* @throws IOException
*/
@RequestMapping(value = "import")
public List<Student> importStudentInfos(MultipartFile file) throws IOException {
StudentListener studentListener = new StudentListener();
EasyExcel.read(file.getInputStream(), Student.class, studentListener).sheet().doRead();
return studentListener.getStudentList();
}
}
- 创建文件读取写入Controller示例
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.alibaba.excel.EasyExcel;
import com.c3stones.entity.Student;
import com.c3stones.listener.StudentListener;
/**
* 文件Controller
*
* @author CL
*
*/
@RestController
@RequestMapping(value = "file")
public class FileController {
/**
* 读取Excel
*
* @return
*/
@RequestMapping(value = "readExcel")
public List<Student> readExcel() {
String fileName = "C:\\\\Users\\\\Administrator\\\\Desktop\\\\学生花名册.xlsx";
StudentListener studentListener = new StudentListener();
EasyExcel.read(fileName, Student.class, studentListener).sheet().doRead();
return studentListener.getStudentList();
}
/**
* 写入Excel
*
* @return
* @throws ParseException
*/
@SuppressWarnings("serial")
@RequestMapping(value = "writeExcel")
public Boolean writeExcel() throws ParseException {
String fileName = "C:\\\\Users\\\\Administrator\\\\Desktop\\\\学生花名册2.xlsx";
List<Student> studentList = new ArrayList<Student>() {
{
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
add(new Student("2001", "张三2", 23, "男", "陕西西安", dateFormat.parse("2020-09-01")));
add(new Student("2002", "李四2", 22, "女", "陕西渭南", dateFormat.parse("2020-09-01")));
}
};
EasyExcel.write(fileName, Student.class).sheet("学生信息2").doWrite(studentList);
return true;
}
}
- 创建启动类
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* 启动类
*
* @author CL
*
*/
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
- 启动项目
3. 测试
通过Postman依次测试导出、导入、读取和写入：
- 测试导出
将导出文件保存到桌面（学生花名册.xlsx）。 - 测试导入
- 测试读取
- 测试写入
可以看到在代码中配置的文件目录已存在写入成功的文件（学生花名册2.xlsx）。