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getitemblob方法来提取数据库外部的blob。在下一步中，我将在controller类中创建getitemimage方法。这些方法通过itemid在inputstream和servletoutputstream的最后一步中转换blob来搜索数据库中正确的blob。
在html部分，我使用了一个普通的img标记，并将服务器主机名、端口和getitemimage方法Map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（订户控制器）

@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;
}

离子型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>

离子型字体/角型

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;
    });
}