如何在Java中将查询字符串值从servlet传递到jsp（文本框值）

Question

基于查询字符串值，我需要从数据库获取值，并且需要将值从servlet传递到jsp，我如何在这里传递该值，我尝试了此代码在文本框中显示为null值。

Answer 1

您必须使用void setAttribute(java.lang.String name, java.lang.Object o)并且还必须检查ResultSet是否不为空，而必须使用以下方法：

ResultSet res = st.executeQuery(s);
int id = 0;
if(res.next()){
   id = res.getInt("BatchID");
}
request.setAttribute("BatchID", id);

---

请注意，为避免任何语法错误或SQL注入，您必须改用PreparedStatement

String s = "select BatchID from CPWorkDetails where BatchId = ?";
st = conn.createStatement();
ResultSet res = st.executeQuery(s);
int Id = res.getInt("BatchID");

try (PreparedStatement st = connection.prepareStatement(s)) {
    st.setString(1, BatchId1[1]);
    ResultSet res = st.executeQuery(s);
    int id = 0;
    if(res.next()){
       id = res.getInt("BatchID");
    }
    request.setAttribute("BatchID", id);
}

Answer 2

用于此：

request.setAttribute("BatchID", value);

Answer 3

使用request.setAttribute（）方法在servlet中设置BatchID

Servlet

 try {
    conn = ds.getConnection();
    if (request.getQueryString() != null) {
        String Batch = request.getQueryString();
        String[] BatchId1 = Batch.split("=");
        String s = "select BatchID from CPWorkDetails where BatchId='" + BatchId1[1] + "'";
        st = conn.createStatement();
        ResultSet res = st.executeQuery(s);
        int Id = res.getInt("BatchID");
        request.setAttribute("BatchID",Id );
    }
}

Jsp

<input type="text" id="txtBatchName" class="form-control" 
name="txtBatchName" value=" <%=request.getAttribute("BatchID")%>">