java - 使用 Struts 2 在 MySQL 的 JSP 页面中查看图像

Question

我有一个按钮可以拾取图像并将其放入 MySQL 数据库中。在此之后，我希望图像将显示在同一页面中。我是 Struts2 的新手，我现在不知道如何继续。

这是我的类Registrazione.java:

public String visualizzaimg() throws SQLException, IOException {
    Connessione();    // DB connection method
    PreparedStatement pstmt = con.prepareStatement("SELECT Immagine FROM Utenti WHERE Username = ?");
    pstmt.setString(1,username);
    ResultSet rs = pstmt.executeQuery();
    while(rs.next()){
    fin = rs.getBinaryStream("Immagine");
    byte[] b = new byte[fin.available()];
    fin.read(b);
    }
    return "success";
}

这是我的struts.xml 文件:

<action name="visualizzaimg" class="Model.Registrazione" method="visualizzaimg">
<result name="success" type="stream">
        <param name="contentType">image/jpeg</param>
        <param name="inputName">fin</param>
        <param name="contentDisposition">attachment;filename=${fileName}</param> /* Not sure if i've understood what i have to put here.. */
        <param name="bufferSize">1024</param>
    </result>
</action>

这是我的 LoginRiuscito.jsp 页面:

<s:form action="carica" id="carica" style="display:none" enctype="multipart/form-data">
    <s:textfield id="username" name="username" type="hidden"></s:textfield>
    <s:file id="carica" name="caricaimg" accept="image/*"></s:file>
    <s:submit value="Carica" ></s:submit>
</s:form>
<s:form action="visualizzaimg" enctype="multipart/form-data">
    <s:textfield id="username" name="username" type="hidden"></s:textfield>
    <img src="">  //i don't know what i have to put in src..
    <s:submit value="Visualizza"></s:submit>
</s:form>

Answer 1

重点是将url写入<img>标签。该 url 应该映射一个将流数据流式传输到响应的操作。

<img src="<s:url action='visualizzaimg'/>">  

该操作需要返回一个 stream结果，为此它应该为 InputStream 提供一个 getter .输入流的默认输入名称是 inputStream , 所以我们将使用它。

private InputStream inputStream;

public ImputStream getInputStream(){
  return inputStream;
}

public String visualizzaimg() throws SQLException, IOException {
    Connessione();    // DB connection method
    PreparedStatement pstmt = con.prepareStatement("SELECT Immagine FROM Utenti WHERE Username = ?");
    pstmt.setString(1,username);
    ResultSet rs = pstmt.executeQuery();
    if(rs.next()){
      inputStream = rs.getBinaryStream(1);
    }
    return "success";
}

现在配置结果

<result name="success" type="stream">
   <param name="contentType">image/jpeg</param>
</result>