0
我想保存一個註釋，我使用的是來自客戶表的外鍵（c_id），但它說外鍵約束不能添加或更新數據庫「無法添加或更新子行：外鍵約束失敗」
"Cannot add or update a child row: a foreign key constraint fails
(`db_hotel`.`tbl_comments`, CONSTRAINT `tbl_comments_ibfk_1` FOREIGN KEY (`c_id`)"
我的實體類
public class Comments {
private int commentsId;
private Customer customer;
private String message;
public Comments() {
}
public Comments(int commentsId, Customer customer, String message) {
this.commentsId = commentsId;
this.customer = customer;
this.message = message;
}
public int getCommentsId() {
return commentsId;
}
public void setCommentsId(int commentsId) {
this.commentsId = commentsId;
}
public Customer getCustomer() {
return customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
@Override
public String toString() {
return "Comments{" + "commentsId=" + commentsId + ", customer=" + customer + ", message=" + message + '}';
}
}
我實現部分爲CRUD操作
@Repository(value = "CommentsDAO")
public class CommentsDAOImpl implements CommentsDAO {
@Autowired
private JdbcTemplate jdbcTemplate;
@Override
public List<Comments> getALL() throws SQLException {
return jdbcTemplate.query(SQLConstant.COMMENTS_GETALL, new RowMapper<Comments>() {
@Override
public Comments mapRow(ResultSet rs, int i) throws SQLException {
return mapData(rs);
}
});
}
@Override
public int insert(Comments comm) throws SQLException {
return jdbcTemplate.update(SQLConstant.COMMENTS_INSERT, new Object[]{comm.getCommentsId(), comm.getCustomer().getC_id(), comm.getMessage()});
}
private Comments mapData(ResultSet rs) throws SQLException {
Comments comments = new Comments();
comments.setCommentsId(rs.getInt("comments_id"));
Customer customer = new Customer();
customer.setC_id(rs.getInt("c_id"));
customer.setFirstName(rs.getString("first_name"));
customer.setLastName(rs.getString("last_name"));
customer.setEmail(rs.getString("email"));
customer.setContactNo(rs.getInt("contact_no"));
comments.setCustomer(customer);
comments.setMessage(rs.getString("message"));
return comments;
}
@Override
public int update(Comments comm) throws SQLException {
return jdbcTemplate.update(SQLConstant.COMMENTS_UPDATE, new Object[]{comm.getMessage(), comm.getCustomer().getC_id(), comm.getCommentsId()});
}
@Override
public int delete(int commentsId) throws SQLException {
return jdbcTemplate.update(SQLConstant.CUSTOMER_DELETE, new Object[]{commentsId});
}
@Override
public Comments getById(int commentsId) throws SQLException {
return (Comments) jdbcTemplate.query(SQLConstant.COMMENTS_GETBYID, new Object[]{commentsId}, new ResultSetExtractor<Comments>() {
@Override
public Comments extractData(ResultSet rs) throws SQLException, DataAccessException {
Comments comments = null;
if (rs.next()) {
comments = new Comments();
comments.setCommentsId(rs.getInt("comments_id"));
Customer customer = new Customer();
customer.setC_id(rs.getInt("c_id"));
customer.setFirstName(rs.getString("first_name"));
customer.setLastName(rs.getString("last_name"));
customer.setEmail(rs.getString("email"));
customer.setContactNo(rs.getInt("contact_no"));
comments.setCustomer(customer);
comments.setMessage(rs.getString("message"));
}
return comments;
}
});
}
}
控制器部分
@Controller
@RequestMapping(value="/admin/comments")
public class CommentsController {
@Autowired
private CommentsService commentsService;
@Autowired
private CustomerService customerService;
@RequestMapping(method = RequestMethod.GET)
public String index (ModelMap map) throws SQLException{
map.addAttribute("Comments",commentsService.getALL());
return "admin/comments/index";
}
@RequestMapping(value="/add",method=RequestMethod.GET)
public ModelAndView add(HttpServletRequest request) throws SQLException {
ModelAndView mv= new ModelAndView("/admin/comments/add");
String c_id=null;
if (request.getParameter("c_id")!=null && !request.getParameter("c_id").equals("")) {
c_id=request.getParameter("c_id");
}
mv.addObject("Customer", customerService.getALL());
return mv;
}
@RequestMapping(value = "/delete/{commentsId}",method = RequestMethod.GET)
public String delete(@PathVariable("commentsId") int commentsId)throws SQLException {
commentsService.delete(commentsId);
return "redirect:/admin/comments";
}
@RequestMapping(value="/save",method=RequestMethod.POST)
public String save(@ModelAttribute ("Comments")Comments comment, @ModelAttribute("Customer")Customer customer) throws SQLException {
try {
comment.setCustomer(customer);
if(comment.getCommentsId()==0) {
commentsService.insert(comment);
} else {
commentsService.update(comment);
}
} catch (SQLException ex) {
}
return "redirect:/admin/comments";
}
}
這裏是JSP插入或ADD
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<h1>Add Users</h1>
<form:form modelAttribute="Comments" action="${SITE_URL}/admin/comments/save" method="post" role="form">
<div class="form-group">
<label for="c_id">CustomerId</label>
<select path="c_id" class="form-control">
<option value="0">Select Commentor</spring:option>
<c:forEach var="customer" items="${Customer}">
<option value="${customer.getC_id()}">${customer.getFirstName()}
</option>
</c:forEach>
</select>
</div>
<div class="form-group">
<label>Message</label>
<form:input path ="message" placeholder="Enter Message" required="required" class="form-control"/>
</div>
<form:hidden path="commentsId"/>
<div class="form-group">
<button type="submit" class="btn btn-success" >Save</button>
</div>
</form:form>
我想solvde它由於兩個天，但無法弄清楚..
外部約束錯誤意味着在Customer表中找不到引用的Customer（by c_id） - 但這也可能意味着您傳遞了null值。您是否已檢查並確認該客戶存在 - 並且您確實通過了客戶ID？ – ishmaelMakitla
客戶表存在，當我嘗試直接從MySQL插入它的作品，但是當我嘗試從jsp插入它給了我上述錯誤。並在選擇選項我從客戶表中獲取客戶的所有名稱 –