代码

    /**
     * easyexcel大数据量（百万数据）,写入到excel
     */
    @Test
    void bigData() throws FileNotFoundException {
        //输出流，确定文件存放位置
        FileOutputStream fileOutputStream = new FileOutputStream("E:\\tmp\\user.xlsx");
        //所有数据
        ArrayList<User> users = new ArrayList<>();
        for (int i = 0; i < 100 * 30000; i++) {
            User user = new User();
            user.setCjsj(new Date().toString());
            user.setId(i);
            user.setLxfs(i + "");
            user.setYxds("广州");
            user.setTzqy("广东");
            users.add(user);
        }
        //将数据切分成多个，放置到不同的sheet
        ArrayList<List<User>> objects = new ArrayList<>();
        int size = 100 * 200;
        int sheetNum = users.size() / size + (users.size() % size > 0 ? 1 : 0);
        for (int i = 0; i < sheetNum; i++) {
            objects.add(users.subList(i * size, (i + 1) * size <= users.size() ? (i + 1) * size : users.size()));
        }
        ExcelWriter build = EasyExcel.write(fileOutputStream, User.class)
                .build();
        //将数据写入到excel，循环写入
        for (int i = 0; i < objects.size(); i++) {
            build.write(objects.get(i), EasyExcel.writerSheet("表格" + i).build());
        }
        build.finish();
    }

从数据库实现

  @Test
    void sqlexport() throws FileNotFoundException {
        //输出流，确定文件存放位置
        FileOutputStream fileOutputStream = new FileOutputStream("E:\\tmp\\user.xlsx");
        ExcelWriter build = EasyExcel.write(fileOutputStream, User.class)
                .build();
        //1.查询数据量大小
        Integer number = fileService.querySum();
        int size = 100 * 1000;
        //2.计算有多少个sheet
        int sheetNum = number / size + (number % size > 0 ? 1 : 0);
        //3.循环写入
        for (int i = 0; i < sheetNum; i++) {
            List<User> users = fileService.queryUserByPage(i * size, size);
            build.write(users, EasyExcel.writerSheet("表格" + i).build());
        }
        //4.关闭流
        build.finish();
    }

dao层

 /**
     * 查询数据量有多少
     */
    public Integer querySum() {
        String sql = "select count(*) from user";
        Integer integer = jdbcTemplate.queryForObject(sql, Integer.class);
        return integer > 0 ? integer : 0;
    }

    /**
     * 分页查询数据
     *
     * @param start
     * @param size
     * @return
     */
    public List<User> queryUserByPage(Integer start, Integer size) {
        //开始位置，拿多少数据（]
        String sql = String.format("select * from user limit %s,%s", start, size);
        List<User> users = jdbcTemplate.query(sql, new BeanPropertyRowMapper<>(User.class));
        return users;
    }