2020-11-28 File Upload in Salesf

文件上传功能 Salesforce有提供专门的组件，具体可以参考下面的链接：
https://developer.salesforce.com/docs/component-library/bundle/lightning-file-upload/documentation
具体实现方式为：这种情况通常是你在一个Object上去Upload文件，而这个Object的Record已经存在了。

<template>
    <lightning-file-upload
            label="Attach receipt"
            name="fileUploader"
            accept={acceptedFormats}
            record-id={myRecordId}
            onuploadfinished={handleUploadFinished}
            multiple>
    </lightning-file-upload>
</template>

import { LightningElement, api } from 'lwc';
export default class FileUploadExample extends LightningElement {
    @api
    myRecordId;
    get acceptedFormats() {
        return ['.pdf', '.png'];
    }
    handleUploadFinished(event) {
        // Get the list of uploaded files
        const uploadedFiles = event.detail.files;
        alert("No. of files uploaded : " + uploadedFiles.length);
    }
}

还有另一个情况是，你在upload文件之后，在去保存这条记录，而这时该记录还没有存在这个时候就需要我们使用其他组件并且在Apex里面做一些特殊处理了：
首先在组件上我们选用 Lightning input, 具体如下：

<lightning-input type="file" onchange={onFileUpload} name="uploadFile" label="Upload File"></lightning-input>    

在JS里面的处理是如下，针对File的解析处理：

 onFileUpload(event) {
        if (event.target.files.length > 0) {
            this.uploadedFiles = event.target.files;
            console.log(' this.uploadedFiles ' + this.uploadedFiles);
            this.fileName = event.target.files[0].name;
            this.file = this.uploadedFiles[0];
        }

        this.fileReader = new FileReader();
        this.fileReader.onloadend = (() => {
            this.fileContents = this.fileReader.result;
            let base64 = 'base64,';
            this.content = this.fileContents.indexOf(base64) + base64.length;
            this.fileContents = this.fileContents.substring(this.content);
            console.log('this.fileContents ' + JSON.stringify(this.fileContents));

            this.fileListsLocal.push({
                file: encodeURIComponent(this.fileContents),
                fileName: this.fileName,
                lastModifiedDate: Date.now(),
                createdBy: this.currentUserName,
                FileType: this.fileName.lastIndexOf(".") < 0? 'UNKNOWN' : (this.fileName.substr((this.fileName.lastIndexOf(".") + 1), this.fileName.length)).toLocaleUpperCase(),
                fileSize: this.formatFileSizeBinary(this.file.size),
                iconType: this.fileName.lastIndexOf(".") < 0? 'unknown' : this.formatIconType((this.fileName.substr((this.fileName.lastIndexOf(".") + 1), this.fileName.length)))
            });
            console.log('this.fileListsLocal. ' + JSON.stringify(this.fileListsLocal));
            if(this.fileListsLocal !== null && this.fileListsLocal.length > 0){
                const selectedEvent = new CustomEvent('saveattachfiles', {
                    detail: {
                        fileInfoList: this.fileListsLocal
                    },
                });
                this.dispatchEvent(selectedEvent);
            }
        });
        this.fileReader.readAsDataURL(this.file);
    }

在Apex中，对该Record的保存逻辑为：

    @AuraEnabled
    public static void documentLinkwithTask(String taskId, String fileInfoList){
        System.debug('taskId '+taskId);
    try{
        List<ContentVersion> contenList = new List<ContentVersion>();
        List<FileWrapper> fileInfoList1 =  (List<FileWrapper>)JSON.deserialize(fileInfoList,List<FileWrapper>.class);
        for(FileWrapper wrapper: fileInfoList1){
        System.debug('wrapper '+wrapper);    
        ContentVersion contentVersionRec = new ContentVersion();  
        contentVersionRec.Title = wrapper.fileName;  
        contentVersionRec.PathOnClient = '/' + wrapper.fileName;  
        contentVersionRec.FirstPublishLocationId = taskId;
        // String base64Content = ( String ) JSON.deserialize(wrapper.file, String.class );
        String base64File = EncodingUtil.urlDecode(wrapper.file, 'UTF-8'); 
        contentVersionRec.VersionData = EncodingUtil.base64Decode(base64File);  
        contentVersionRec.IsMajorVersion = true; 
        contenList.add(contentVersionRec); 
        }
        Insert contenList;
    }catch (Exception e) {
        //throw exception
        //System.debug('e.getMessage()-->'+e.getMessage() +' - '+e.getStackTraceString());
        throw new AuraHandledException('Something went wrong: '+e.getMessage() );
    }
    }

下面的逻辑为获得某对象上关联的所有文件的代码：

 public static List<ContentDocument> getTaskRelatedFiles(String taskId){
        try{
           List<String> contentDocumentIds = new List<String>();
           List<ContentDocumentLink> docLinks = 
           [SELECT ContentDocumentId,Id,IsDeleted,LinkedEntityId,ShareType,SystemModstamp,Visibility 
           FROM ContentDocumentLink WHERE LinkedEntityId =: taskId];
           for(ContentDocumentLink docLink: docLinks){
              contentDocumentIds.add(docLink.ContentDocumentId);
           }

            List<ContentDocument> documents = 
                [SELECT ContentAssetId,
                    ContentModifiedDate,
                    ContentSize,
                    CreatedById,
                    CreatedBy.Name,
                    CreatedDate,
                    Description,
                    FileExtension,
                    FileType,
                    Id,
                    IsDeleted,
                    LastModifiedById,
                    LastModifiedDate,
                    LastReferencedDate,
                    LastViewedDate,
                    LatestPublishedVersionId,
                    OwnerId,
                    PublishStatus,
                    Title 
                FROM ContentDocument
                WHERE Id 
                IN: contentDocumentIds
                ];
            return documents;
        }catch(Exception e){
            throw new AuraHandledException('Something went wrong: '+e.getMessage());
        }
    }