如何在 Angular 应用程序中显示 MySQL Blob？

Question

我使用 MYSQL Blob 将图像存储在数据库中。现在我想在我上传的 IONIC 应用程序中显示图像。

它是如何工作的以及如何将它存储在一个对象中？

你可以在这里找到我的代码：

Java 类

    public JSONObject getItems(String email) throws SQLException, ClassNotFoundException, IOException {
    JSONObject jsonObject = new JSONObject();
    JSONArray jsonArray = new JSONArray();


    Connection conn = new MYSQLAccess().getConnection();        
    String sql = "SQL String";
    PreparedStatement pstm = conn.prepareStatement(sql);

    pstm.setString(1, email);

    ResultSet rs = pstm.executeQuery();

    while (rs.next()) {
        jsonObject.put("1", rs.getBlob("1"));
        jsonObject.put("2",rs.getInt("2"));
        jsonObject.put("3", rs.getString("3"));
        jsonObject.put("4", rs.getString("4"));

        jsonArray.add(performanceCarsJsonObject);
    }


    jsonObject = new JSONObject();
    jsonObject.put("array", jsonArray);

    conn.close();
    return jsonObject;
}

TypeScript Ionic/Angular

getPerformanceCars() {
    let params = {"email": this.user.getEmail()};

    this.cars.performanceCars(params).then(data => {
        this._List = data;
        this._List = this._List.value.icons;
        this.itemList = this._List;
    });
}

离子 HTML

<ion-list>
    <ion-item-sliding *ngFor="let items of itemList">
      <button ion-item (click)="openItem(item)">
        <ion-avatar item-start>
            <img [src]="items.img" />
        </ion-avatar>
        <h2>{{ items.email }}</h2>
        <p>{{ items.values }}</p>
        <ion-note item-end *ngIf="items.note">{{ cars.note }}</ion-note>
      </button>
    </ion-item-sliding>
</ion-list>

IONIC Input Uploader 中的照片预览使用以下 HTML 代码。

<div class="profile-image" style="background-image: url(&quot;data:image/jpeg;base64,DATA;);"></div>

我希望你能帮助我，解决我的问题。

Answer 1

解决方案

我通过创建两个新方法解决了这些问题。在第一步中，我创建了 getItemBlob 方法来将 Blob 提取到数据库之外。在下一步中，我在控制器类中创建方法 getItemImage。这些方法通过 itemID 在数据库中搜索正确的 Blob，将 Blob 转换为 InputStream，最后一步转换为 ServletOutputStream。

在 HTML 部分，我使用了一个普通的 img 标签，并将服务器主机名、端口和 getItemImage 方法映射在一起以显示图像。

Java 类（项目服务）

public Blob getItemBlob(String id) throws SQLException{
    Blob image = null;
    
    Connection conn = new MYSQLAccess().getConnection();
    String sql = "SELECT ITEMDATA FROM OWNITEM WHERE OWNITEMID = ? AND ACTIVE = 1";
    PreparedStatement pstm = conn.prepareStatement(sql);
    pstm.setString(1, id);
    ResultSet rs = pstm.executeQuery();
    
    while (rs.next()) {
        image = rs.getBlob("ITEMDATA");
    }
    
    conn.close();
    return image;
}

Java 类（项目控制器）

@ResponseBody
@CrossOrigin(origins = "http://localhost:8100")
@RequestMapping(value = "/getItemImage")
public void getItemImage(@RequestParam("id") String id, HttpServletResponse response) throws IOException, SQLException {
    ServletOutputStream out = response.getOutputStream();
    ItemServices myItemServices = new ItemServices();
    Blob image = myItemServices.getItemBlob(id);
    
    response.setContentType("image/jpg");
    InputStream in = image.getBinaryStream();
    int length = (int)image.length();
    int bufferSize = 1920;
    byte[] buffer = new byte[bufferSize];
    
    while ((length = in.read(buffer)) != -1) {
        out.write(buffer, 0, length);
    }
    
    in.close();
    out.flush();
}

Java 类（订阅者控制器）

@SuppressWarnings("unchecked")
public JSONObject getSubscribersItems(String email) throws SQLException, ClassNotFoundException {
    JSONObject subscribersItemsJsonObject = new JSONObject();
    JSONArray subscribersItemsJsonArray = new JSONArray();
    ArrayList<String> subscribersArrayList = this.getSubscriber(email);
    
    Connection conn = new MYSQLAccess().getConnection();        
    String sql = "SELECT T1.OWNITEMID,T1.ITEMNAME,T2.USERNAME,T2.COUNTRY FROM OWNITEM T1,CUSTOMER T2 WHERE T1.EMAIL = T2.EMAIL AND T1.EMAIL = ? AND T1.ITEMDATA != 'NULL' AND T2.ACTIVE = 1";
    PreparedStatement pstm = conn.prepareStatement(sql);
    
    for (int i = 0; i < subscribersArrayList.size(); i++) {
        pstm.setString(1, subscribersArrayList.get(i));

        ResultSet rs = pstm.executeQuery();
        
        while (rs.next()) {
            subscribersItemsJsonObject = new JSONObject();
            
            subscribersItemsJsonObject.put("itemID", rs.getInt("OWNITEMID"));
            subscribersItemsJsonObject.put("itemName", rs.getString("ITEMNAME"));
            subscribersItemsJsonObject.put("username", rs.getString("USERNAME"));
            subscribersItemsJsonObject.put("country", rs.getString("COUNTRY"));
            
            subscribersItemsJsonArray.add(subscribersItemsJsonObject);
        }
    }

    subscribersItemsJsonObject = new JSONObject();
    subscribersItemsJsonObject.put("items", subscribersItemsJsonArray);
    
    conn.close();
    return subscribersItemsJsonObject;
}

离子 HTML

<ion-list>
    <ion-item-sliding *ngFor="let items of subscriberItemsItemList">
      <button ion-item (click)="openItems(items)">
        <ion-avatar item-start>
            <img src="{{ itemImageUrl }}/getItemImage?id={{ cars.itemID }}" />
        </ion-avatar>
        <h2>{{ items.username }}</h2>
        <p>{{ items.country }}</p>
        <ion-note item-end *ngIf="items.note">{{ items.note }}</ion-note>
      </button>
    </ion-item-sliding>
</ion-list>

IONIC TypeScript/Angular

getDesignCars() {
    let params = {"email": this.user.getEmail()};
    
    this.cars.homeCars(params).then(data => {
        this._subscriberCarsList = data;
        this._subscriberCarsList = this._subscriberCarsList.value.cars;
        this.subscriberCarsItemList = this._subscriberCarsList;
    });
}