How to call a DAO method from a Json Servlet - json

Question

I have a dependency dropdown list in my JSP. I have a json servlet where I populate the second dropdown. Based on the selection made for the first dropdown will determine the second dropdown. I have hardcoded values within the jsonServlet class but I want to be able to call a query from my DAO method. How would I go about this?
JsonServlet:
package master.service;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import master.dao.MasterDataDao;
import master.dto.SiteDto;
import com.google.gson.Gson;
/**
* Servlet implementation class JsonServlet
* #param <E>
*/
public class JsonServlet<E> extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
MasterDataDao masterDataDao = new MasterDataDao();
String divisionIdName = request.getParameter("divisionIdName");
List<String> list = new ArrayList<String>();
List<SiteDto> site = new ArrayList<SiteDto>();
String json = null;
if (divisionIdName.equals("33") || divisionIdName.equals("36")) {
try {
site.equals(masterDataDao.getAllJJSites());
for (Iterator<SiteDto> iter = site.iterator(); iter.hasNext(); ){
SiteDto element = iter.next();
list.addAll(-1, element);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
for (Iterator<SiteDto> iter = site.iterator(); iter.hasNext(); ){
SiteDto element = iter.next();
}
} else if (divisionIdName.equals("Select Division")) {
list.add("Select Site");
} else {
try {
site.equals(masterDataDao.getAllSites());
for (Iterator<SiteDto> iter = site.iterator(); iter.hasNext(); ){
SiteDto element = iter.next();
list.addAll(-1, element);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
json = new Gson().toJson(list);
response.setContentType("application/json");
response.getWriter().write(json);
}
}
Based off the divisionID selection in my JsonServlet, if the divisionID is either 33 or 36 i'd like to call this method in my MasterDataDao class:
public List<SiteDto> getAllJJSites() throws IOException, ClassNotFoundException, SQLException {
List<SiteDto> siteDtoList = new ArrayList<SiteDto>();
Connection con = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
String query = "Select Distinct Name, Id From Addtl_Type Where Addtl_Type.is_active = '1' And Data_Field_Id = 3050 Order By Name";
con = getConnection();
ps = con.prepareStatement(query);
rs = ps.executeQuery();
// System.out.println("&*******" + rs.getFetchSize());
while (rs.next()) {
SiteDto siteDto = new SiteDto();
siteDto.setId(rs.getString("Id"));
siteDto.setName(rs.getString("Name"));
siteDtoList.add(siteDto);
}
} finally {
cleanUp(con, ps, rs);
}
return siteDtoList;
}
Otherwise if it is another selection value(besides Select Division), I'd like to call this method with the MasterDataDao class:
public List<SiteDto> getAllSites() throws IOException, ClassNotFoundException, SQLException {
List<SiteDto> siteDtoList = new ArrayList<SiteDto>();
Connection con = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
String query = "Select Distinct Name, Id From Addtl_Type Where Addtl_Type.is_active = '1' And Data_Field_Id = 105 Order By Name";
con = getConnection();
ps = con.prepareStatement(query);
rs = ps.executeQuery();
// System.out.println("&*******" + rs.getFetchSize());
while (rs.next()) {
SiteDto siteDto = new SiteDto();
siteDto.setId(rs.getString("Id"));
siteDto.setName(rs.getString("Name"));
siteDtoList.add(siteDto);
}
} finally {
cleanUp(con, ps, rs);
}
return siteDtoList;
}
Is this possible to do within the JsonServlet? If so how? Thanks in advance.
Please let me know if more information is needed.
Also I have included my JSP here. Initially I had made a call to the DAO from here. I referenced a bean.
JSP:
<script>
$(document).ready(function() {
$('#divisionId').change(function(event) {
var divisionId = $("select#divisionId").val();
$.get('JsonServlet', {
divisionIdName : divisionId
}, function(response) {
var select = $('#siteId');
select.find('option').remove();
$.each(response, function(index, value) {
$('<option>').val(value).text(value).appendTo(select);
});
});
});
});
</script>
</head>
<body>
<form name="input" action="getMasterData" method="get">
<br /> <br />
<h1 align='center'>Master Data File</h1>
<br /> <br />
<table border="0" align='center'>
<tr>
<td>
<h2>Division</h2>
</td>
<td align='left'><jsp:useBean id="masterDaoUtil"
class="master.dao.util.MasterDataConstants" />
<select name="divisionId" id="divisionId">
<option>Select Division</option>
<option value="33">
<%=MasterDataConstants.DIVISION_TYPE_AUDIT_MANAGEMENT_GLOBAL_NAME%></option>
<option value="31">
<%=MasterDataConstants.DIVISION_TYPE_CHANGE_MANAGEMENT_GLOBAL_NAME%></option>
<option value="34">
<%=MasterDataConstants.DIVISION_TYPE_DEA_MANAGEMENT_GLOBAL_NAME%></option>
<option value="35">
<%=MasterDataConstants.DIVISION_TYPE_EHS_MANAGEMENT_GLOBAL_NAME%></option>
<option value="23">
<%=MasterDataConstants.DIVISION_TYPE_EVENT_MANAGEMENT_GLOBAL_NAME%></option>
<option value="36">
\
<%=MasterDataConstants.DIVISION_TYPE_QUALITY_EVENT_MANAGEMENT_GLOBAL_NAME%></option>
<option value="40">
<%=MasterDataConstants.DIVISION_TYPE_NORAMCO_AUDIT_MANAGEMENT_GLOBAL_NAME%></option>
<option value="43">
<%=MasterDataConstants.DIVISION_TYPE_NORAMCO_CHANGE_MANAGEMENT_GLOBAL_NAME%></option>
<option value="41">
<%=MasterDataConstants.DIVISION_TYPE_NORAMCO_DEA_MANAGEMENT_GLOBAL_NAME%></option>
<option value="42">
<%=MasterDataConstants.DIVISION_TYPE_NORAMCO_EHS_MANAGEMENT_GLOBAL_NAME%></option>
<option value="44">
<%=MasterDataConstants.DIVISION_TYPE_NORAMCO_EVENT_MANAGEMENT_GLOBAL_NAME%></option>
</select></td>
</tr>
<tr>
<td>
<h2>Site Name</h2>
</td>
<td align='left'>
<%-- <jsp:useBean id="masterDao"
class="master.dao.MasterDataDao" />
--%>
<select name="siteId"
id="siteId">
<option>Select Site</option>
<%-- <option value="0">ALL</option>
<c:forEach items="${masterDao.allSites}" var="siteDto">
<option value="${siteDto.id}">${siteDto.name}
</option>
</c:forEach>
--%>
</select></td>
</tr>
</table>
<br /> <br />
<div style="text-align: center">
<input type="submit" value="Submit">
</div>
</form>
<%
if (request.getAttribute("message") != null) {
%>
<p>
<font size=4 color="red"> Master_Data(timestamp).xlsx and
Consistency_Check_Data(timestamp).xlsx are located under
d:/stage/MasterDataReports <%--Master_Data(timestamp).xlsx and Consistency_Check_Data(timestamp).xlsx are located under /jsc/ets/u02/tools7/apache-tomcat-7.0.55/webapps/MasterData/MasterDataReport--%>
</font>
</p>
<%
}
%>
Originally before I used JSON and AJAX I used this statement for the options which is now commented out.
<%-- <jsp:useBean id="masterDao"
class="master.dao.MasterDataDao" />
--%>
<select name="siteId"
id="siteId">
<option>Select Site</option>
<%-- <option value="0">ALL</option>
<c:forEach items="${masterDao.allSites}" var="siteDto">
<option value="${siteDto.id}">${siteDto.name}
Is there a way I can leverage this? Maybe can I make a function call to the JSP from my servlet? I know this is not good practice but I cannot think of another way. I need to get the siteDto.id value as well as the siteDto.name value.
Thanks in advance

Answer 1

Create an interface and implementation DAO like IMasterDataDAO and MasterDataDAOImpl.
In case if you get more if..else condition in future then use switch..case instead of if..else.
Create an object for DAO using the interface in servlet like below:
IMasterDataDAO masterDAO = new MasterDataDAOImpl()
then call either masterDAO.getAllJSites() or masterDAO.getAllSites() based on the condition.