Easyexcel complex header export (one to many)

Preface

Before , Yes EasyExcel Complex header import （ One to many ） The blog of , The result is right , Many netizens left messages asking me to write another imported . difficult to refuse such kindness , Just wrote a , Found a lot of problems .

About EasyPoi Framework issues , No more details here , Refer to my other blog , The address is as follows ：

EasyExcel Complex header import （ One to many ）_ The blog of -CSDN Blog _easyexcel Complex header

actually , There are no detailed export tutorials in official documents or online , You need to refer to the official to realize . I only succeeded in making one and a half barrels of water for a long time , I'm very ashamed , Record here , Convenient back .

explain ：EasyExcel Unable to deal with List It's nested inside List The situation of , The scheme I adopted is realized by merging tables .

below , First, give the specific implementation , Then talk about the problem .

EasyExcel Implementation of one to many export

Entity object

/**
 *  Customer information export class , Indicate the export template style, etc . Is real and EasyPoi Interactive classes 
 */
@Data
@EqualsAndHashCode
@HeadRowHeight(30)
@ContentRowHeight(20)
@ColumnWidth(20)
@HeadStyle(fillForegroundColor = 44)
@NoArgsConstructor
class Customer extends BaseRowModel implements Serializable {

    @ExcelProperty({" Customer number "})
    private String userCode;

    @ExcelProperty({" Customer name "})
    private String userName;

    @ColumnWidth(25)
    @ExcelProperty({" Customer address "})
    private String address;

    @ExcelProperty({" Contact information ", " Contact name "})
    private String personName;

    @ExcelProperty({" Contact information ", " contact number "})
    private String telephone;

    public Customer(CustomerInfo customerInfo) {
        this.userCode = customerInfo.getUserCode();
        this.userName = customerInfo.getUserName();
        this.address = customerInfo.getAddress();
        this.personName = customerInfo.getPersonList().get(0).getPersonName();
        this.telephone = customerInfo.getPersonList().get(0).getTelephone();
    }

    public Customer(CustomerInfo.Person person) {
        this.personName = person.getPersonName();
        this.telephone = person.getTelephone();
    }

}

/**
 *  Basic customer information , Analogy program from service Information obtained by the layer 
 *  actually ,EasyPoi Can only read simple String、boolean、integer、float byte[]  And so on . Unable to deal with List、Map And so on .
 *  At present , You can also define only type converters Converter, See the reference link at the end of the article for details .
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
class CustomerInfo {

    private String userCode;

    private String userName;

    private String address;

    private List<Person> personList;

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    static class Person {
        private String personName;

        private String telephone;
    }

}

Controller layer

@IgnoreUserToken
@GetMapping("/exportExcel")
@ApiOperation(" export Excel")
public void exportExcel(HttpServletResponse response) throws Exception {
    //  Get export data , Simulation from service Get the floor list data .
    List<CustomerInfo> list = getData();
    //  Get all customer information , The largest number of contacts . And take this quantity as the basis for line consolidation 
    int maxColNum = 1;
    for (CustomerInfo ele : list) {
        if (ele.getPersonList().size() > maxColNum) {
            maxColNum = ele.getPersonList().size();
        }
    }

    //  Arrangement , speak List contain List Data format , Change to List The format of 
    final int finalMaxColNum = maxColNum;
    List<Customer> result = list.stream()
            .flatMap(ele -> {
                List<Customer> temp = new ArrayList<>();
                //  Get the number of current customer contacts 
                int len = ele.getPersonList().size();
                //  First add a complete customer information 
                temp.add(new Customer(ele));
                for (int i = 1; i < finalMaxColNum; i++) {
                    if (i >= len) {
                        //  To reach maxColNum Of , repair null placeholder .
                        temp.add(new Customer());
                    } else {
                        //  Only add contact information 
                        temp.add(new Customer(ele.getPersonList().get(i)));
                    }
                }
                return temp.stream();
            }).collect(Collectors.toList());

    //  Set up excel Header style 
    WriteSheet sheet = EasyExcel.writerSheet(" Customer information ").head(Customer.class).sheetNo(1).build();
    //  Set up excel Table style 
    ExcelWriter writer = EasyExcel.write(response.getOutputStream()).needHead(true).excelType(ExcelTypeEnum.XLSX)
            .registerWriteHandler(new LoopMergeStrategy(maxColNum, 0))  //  Set the first column every maxColNum merger 
            .registerWriteHandler(new LoopMergeStrategy(maxColNum, 1))  //  Set the second column every maxColNum merger 
            .registerWriteHandler(new LoopMergeStrategy(maxColNum, 2))  //  Set the third column every maxColNum merger 
            .build();
    //  write in excel data 
    writer.write(result, sheet);
    //  Notify the browser to download and process in the form of attachment , When setting the return header, note that the file name has Chinese 
    response.setHeader("Content-disposition", "attachment;filename=" + new String(" Customer information list ".getBytes("gb2312"), "ISO8859-1") + ".xlsx");
    response.setContentType("multipart/form-data");
    response.setCharacterEncoding("utf-8");
    writer.finish();
}

getDate Method （ Used to simulate service Data obtained by layer ）

public static List<CustomerInfo> getData() {

    List<CustomerInfo> data = new ArrayList<>();

    CustomerInfo customer = new CustomerInfo();
    customer.setUserCode("CT_jx001");
    customer.setUserName(" Jiangxi Telecom Company ");
    customer.setAddress(" Qingshanhu District, Nanchang City, Jiangxi Province ");
    CustomerInfo.Person person1 = new CustomerInfo.Person(" Zhang San ", "12345678910");
    CustomerInfo.Person person2 = new CustomerInfo.Person(" Li Si ", "10987654321");
    List<CustomerInfo.Person> personList = new ArrayList<>();
    personList.add(person1);
    personList.add(person2);
    customer.setPersonList(personList);
    data.add(customer);

    CustomerInfo customer2 = new CustomerInfo();
    customer2.setUserCode("CT_jx002");
    customer2.setUserName(" Guangdong Telecom Company ");
    customer2.setAddress(" Huadu District, Guangzhou City, Guangdong Province ");
    CustomerInfo.Person person12 = new CustomerInfo.Person(" Xiao Ming ", "12345678910");
    CustomerInfo.Person person22 = new CustomerInfo.Person(" Xiaohong ", "10987654321");
    CustomerInfo.Person person23 = new CustomerInfo.Person(" Xiao Wang ", "12345678910");
    List<CustomerInfo.Person> personList2 = new ArrayList<>();
    personList2.add(person12);
    personList2.add(person22);
    personList2.add(person23);
    customer2.setPersonList(personList2);
    data.add(customer2);

    return data;
}

effect

Interface is get Type of , Browser direct access , Download the file , The effect is as follows .

By the way debug effect , Easy to understand .

debug effect

Problems and Prospects

The problem of this method can be seen from the implementation effect , There will be blank lines .

however , This empty line cannot be avoided , Because multiple rows merge , Only according to the maximum value , And it cannot be dynamically adjusted .

This way, , Although it can realize the export of complex headers , But the display is not satisfactory , Mainly because of the problem of empty lines .

I really can't find a better solution , Only the following ideas are provided here .

You can also pass EasyPoi Of Custom interceptors 、 Data format converter 、 Template write 、 merge cell 、 Write repeatedly And so on .

Reference link

In addition to the official website address , Refer to the following article .

Can not find ‘Converter‘ support class List Problem solving _ I took this nickname and it was never used ？ The blog of -CSDN Blog question description com.alibaba.excel.exception.ExcelDataConvertException: Can not find ‘Converter’ support class List. Problem explanation EasyExcel In the open source framework Converter Interface convertToExcelData Only the conversion BigDecimal、Bolean、Byte[]、btye[]、Byte、Date、Double、File、Float、InputStream、Integer、Long、Short、URL these [ Here is the picture 006]https://blog.csdn.net/qq_41049371/article/details/120156305EasyExcel ExcelDataConvertException:Can not find ‘Converter‘ support class ArrayList Problem solving _ Xudong monster's blog -CSDN Blog question description ：com.alibaba.excel.exception.ExcelDataConvertException:Cannotfind’Converter’supportclassArrayList. Problem analysis ：1、 see doWrite(List data) Source code found when Converter Interface convertToExcelData Only the conversion BigDecimal、Bolean、Byte[]、btye[]、Byte、Date、Double、File、Float、InputStream、…[ Here is the picture 007]https://blog.csdn.net/qq_38974638/article/details/116609844