How to Pass Query String value from servlet to jsp(text box value) in java

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

You have to use void setAttribute(java.lang.String name, java.lang.Object o) also you have to check if your ResultSet is not empty, you have to use this instead :

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

---

Note to avoid any syntax error or sql injection you have to use PreparedStatement instead

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

set BatchID in servlet using request.setAttribute() method

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")%>">