有人可以在这里提供帮助。我有下面的servlet类，每次我尝试从父类别中选择时，没有任何内容显示在子类别中。如果我做错了，请看下面的内容。
由于
ajax部分：
$('#parentCategorySelector').change(function () {
var selectedValue = $(this).prop('value');
if (selectedValue == '--Select a parent category--') {
$('#categorySelector').empty();
} else {
$.post('${PREFIX}/category', selectedValue, function(data) {
var categorySelectorList = data.categorySelectorList;
$('#categorySelector').empty();
$.each(categorySelectorList, function(key, value) {
$('#categorySelector').append($('<option/>', {
value : value,
text : value
}));
});
}, 'json');
}
});
servlet类：
public class CategoryServlet extends HttpServlet {
/**
* serialization
*/
private static final long serialVersionUID = -2461387206258395143L;
private static final Logger LOGGER = Logger
.getLogger(CategoryServlet.class);
private Connection connection = null;
int cat = 0;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
connection = DBConnection.getConnection();
RequestDispatcher dispatcher = request
.getRequestDispatcher("pages/all.jsp");
dispatcher.include(request, response);
String id = request.getParameter("id");
String category = request.getParameter("category");
String parentCategory = request.getParameter("parentCategory");
if (StringUtils.paramSet(id)) {
request.setAttribute("CATEGORY", CategoryService.getCategoryById(
Long.valueOf(id), connection));
} else if (StringUtils.paramSet(parentCategory)) {
request.setAttribute(
"CATEGORY",
CategoryService.getParentCategory(
Integer.valueOf(parentCategory), connection));
} else if (StringUtils.paramSet(category)) {
String categories = request.getParameter("category");
if (StringUtils.paramSet(categories)) {
request.setAttribute("CATEGORY",
CategoryService.listAllCategory(cat, connection));
}
dispatcher = request.getRequestDispatcher("jsp/pages/all.jsp");
} else {
request.setAttribute("CATEGORY",
CategoryService.listAllCategory(cat, connection));
}
dispatcher.include(request, response);
DBConnection.closeConnection(connection);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String action = request.getParameter("action");
LOGGER.info("TESTING " + action);
if (StringUtils.paramSet(action)) {
connection = DBConnection.getConnection();
Map<String, Object> resp = new HashMap<String, Object>();
// resp.put("error", "Please fill in all fields");
List<Category> categorySelectorList =
CategoryService.listAllCategory(cat,connection);
LOGGER.info("TESTING " + categorySelectorList);
// resp.put("categorySelectorList", categorySelectorList);
// LOGGER.info("TESTING 2 " + categorySelectorList);
try {
ResponseUtils.writeJson(resp, response);
} catch (Exception e) {
response.setContentType("application/json");
response.getWriter()
.write("{\"error\" : \"An error occured please try again. If the error persists, please refresh your browser \"}");
}
DBConnection.closeConnection(connection);
}
}
}
并且在jsp中看起来像这样：
<div class="control-group">
<label class="control-label" for="selectError">Select
Category</label>
<div class="controls">
<select id="parentCategorySelector" name="parentCategorySelector"
data-rel="chosen">
<c:forEach items="${PARENTCATEGORY}" var="parentcategory">
<option value="${parentcategory.name}">
<c:out value="${parentcategory.name}" />
</option>
</c:forEach>
</select>
</div>
</div>
<div class="control-group">
<label class="control-label" for="selectError">Select
type</label>
<div class="controls">
<select id="categorySelector" name="categorySelector"
data-rel="chosen">
<c:forEach items="${CATEGORY}" var="subcategory">
<option value="${subcategory.category}">
<c:out value="${subcategory.category}" />
</option>
</c:forEach>
</select>
</div>
</div>
答案 0 :(得分：1)
尝试改变这一点：
var selectedValue = $(this).prop('value');
到此：
var selectedValue = this.value; //<---using navtive js code is better
和
改变这个：
$.post('${PREFIX}/category', selectedValue, function(data) {
到此：
$.post('${PREFIX}/category', {parentCategory:selectedValue}, function(data) {
由于您在请求参数中使用了'parentCategory'，因此您必须按照建议（ $.post ）将其传递到{parentCategory:selectedValue}函数中。
答案 1 :(得分：0)
在ajax部分，我将其改为
$('#parentCategorySelector').change(function () {
var selectedValue = this.value;
if (selectedValue == '--Select a parent category--') {
$('#categorySelector').empty();
} else {
$.post('${PREFIX}/category', {parentCategory:selectedValue}, function(data) {
$('#categorySelector').empty();
$.each(data.categorySelectorList, function(key, value) {
$('#categorySelector').append($('<option/>', {
value : value['id'],
text : value['category']
}));
});
}, 'json');
}
});
servlet类：
public class CategoryServlet extends HttpServlet {
/**
* serialization
*/
private static final long serialVersionUID = -2461387206258395143L;
private static final Logger LOGGER = Logger
.getLogger(CategoryServlet.class);
private Connection connection = null;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
connection = DBConnection.getConnection();
RequestDispatcher dispatcher = request
.getRequestDispatcher("jsp/pages/create.jsp");
dispatcher.include(request, response);
String id = request.getParameter("id");
String category = request.getParameter("category");
String parentCategory = request.getParameter("parentCategory");
if (StringUtils.paramSet(id)) {
request.setAttribute("CATEGORY", CategoryService.getCategoryById(
Long.valueOf(id), connection));
} else if (StringUtils.paramSet(parentCategory)) {
request.setAttribute(
"CATEGORY",
CategoryService.getParentCategory(
Integer.valueOf(parentCategory), connection));
} else if (StringUtils.paramSet(category)) {
String categories = request.getParameter("category");
if (StringUtils.paramSet(categories)) {
request.setAttribute(
"CATEGORY",
CategoryService.listAllCategory(
Integer.valueOf(parentCategory), connection));
}
dispatcher = request.getRequestDispatcher("jsp/pages/create.jsp");
} else {
request.setAttribute(
"CATEGORY",
CategoryService.listAllCategory(
Integer.valueOf(parentCategory), connection));
}
dispatcher.include(request, response);
DBConnection.closeConnection(connection);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int parentCategory = Integer.parseInt(request.getParameter("parentCategory"));
LOGGER.info("parentCategory id : " + parentCategory);
connection = DBConnection.getConnection();
Map<String, List<Category>> resp = new HashMap<String, List<Category>>();
List<Category> categorySelectorList = CategoryService
.listAllCategory(parentCategory,
connection);
resp.put("categorySelectorList", categorySelectorList);
response.setContentType("application/json");
try {
Gson gson = new Gson();
String s = gson.toJson(resp);
response.getWriter().write(s);
LOGGER.info("TESTING mmmm : " + s);
} catch (Exception e) {
response.getWriter()
.write("{\"error\" : \"An error occured please try again. If the error persists, please refresh your browser \"}");
}
DBConnection.closeConnection(connection);
}
}
并在jsp中修改如下：
<div class="control-group">
<label class="control-label" for="selectError2">Select
Category</label>
<div class="controls">
<select id="parentCategorySelector" name="parentCategorySelector"
data-rel="chosen">
<option value="">--Select Category--</option>
<c:forEach items="${PARENTCATEGORY}" var="parentcategory">
<option value="${parentcategory.id}">
<c:out value="${parentcategory.name}" />
</option>
</c:forEach>
</select>
</div>
</div>
<div class="control-group">
<label class="control-label" for="selectError2">Select
type</label>
<div class="controls">
<select id="categorySelector" name="categorySelector"
data-rel="chosen">
</select>
</div>
</div>
以上工作正常。
谢谢大家。