Java 如何在servlet中使用json对象返回项数组以及如何使用jquery显示
我需要将一些项目从数据库传递到网页。为此,我使用json对象将项目从servlet传递到jquery。但问题是Java 如何在servlet中使用json对象返回项数组以及如何使用jquery显示,java,jquery,json,servlets,Java,Jquery,Json,Servlets,我需要将一些项目从数据库传递到网页。为此,我使用json对象将项目从servlet传递到jquery。但问题是 如果数据库包含更多元素 然后我显然需要使用ArrayList 当我使用ArrayList时,我不知道如何通过JSON传递元素 我的代码是: PrintWriter out = response.getWriter(); response.setContentType("text/html"); response.setHeader("Cache-contro
- 如果数据库包含更多元素
- 然后我显然需要使用
ArrayList
- 当我使用
时,我不知道如何通过ArrayList
传递元素JSON
PrintWriter out = response.getWriter();
response.setContentType("text/html");
response.setHeader("Cache-control", "no-cache, no-store");
response.setHeader("Pragma", "no-cache");
response.setHeader("Expires", "-1");
response.setHeader("Access-Control-Allow-Origin", "*");
response.setHeader("Access-Control-Allow-Methods", "GET");
response.setHeader("Access-Control-Allow-Headers", "Content-Type");
response.setHeader("Access-Control-Max-Age", "86400");
Gson gson = new Gson();
JsonObject myObj = new JsonObject();
ArrayList<Commenter> commentInfo;
try {
commentInfo = commenting(uname,message,itemId,albumId);
JsonElement commentObj = gson.toJsonTree(commentInfo);
boolean nonNullElemExist= true;
for (Commenter s: commentInfo) {
if (s == null) {
nonNullElemExist = false;
break;
}
}
if(nonNullElemExist == false){
myObj.addProperty("success", false);
}
else {
myObj.addProperty("success", true);
}
myObj.add("commentInfo", commentObj);
out.println(myObj.toString()); // I think problem is in this statement
out.close();
} catch (ClassNotFoundException | SQLException e) {
System.out.println( "Error --> " + displayErrorForWeb(e));
}
PrintWriter out=response.getWriter();
response.setContentType(“text/html”);
setHeader(“缓存控制”,“无缓存,无存储”);
setHeader(“Pragma”,“无缓存”);
setHeader(“Expires”、“-1”);
response.setHeader(“访问控制允许原点“,“*”);
setHeader(“访问控制允许方法”、“获取”);
setHeader(“访问控制允许头”,“内容类型”);
setHeader(“访问控制最大年龄”,“86400”);
Gson Gson=新的Gson();
JsonObject myObj=新的JsonObject();
ArrayList commentInfo;
试一试{
commentInfo=评论(uname、message、itemId、albumId);
JsonElement commentObj=gson.toJsonTree(commentInfo);
布尔非NullElemexist=true;
对于(评论人s:commentInfo){
如果(s==null){
nonNullElemExist=false;
打破
}
}
if(nonNullElemExist==false){
myObj.addProperty(“成功”,假);
}
否则{
myObj.addProperty(“成功”,真实);
}
添加(“commentInfo”,commentObj);
out.println(myObj.toString());//我认为问题出在这个语句中
out.close();
}catch(ClassNotFoundException | SQLException e){
System.out.println(“错误-->”+displayErrorForWeb(e));
}
方法是:
private ArrayList<Commenter> commenting(String uname,String message,int itemId,int albumId) throws ClassNotFoundException, SQLException {
ArrayList<Commenter> commentList = new ArrayList<Commenter>();
Connection conn = null;
conn=prepareConnection();
PreparedStatement stmt = null;
String sql = null;
try {
StringBuilder sb1=new StringBuilder(1024);
sb1.append("insert into ").append(uname.trim()).append("comments values(?,?,?)");
String sql1=sb1.toString();
PreparedStatement stmt1 = conn.prepareStatement(sql1);
stmt1.setString(1,uname);
stmt1.setString(2,message);
stmt1.setInt(3,itemId);
StringBuilder sb=new StringBuilder(1024);
sb.append("select * from ").append(uname.trim()).append("comments");
sql=sb.toString();
stmt = conn.prepareStatement(sql);
ResultSet rs = stmt.executeQuery();
while(rs.next()){
Commenter comment = new Commenter();
comment.setUname(rs.getString("uname").trim());
comment.setComment(rs.getString("comment").trim());
commentList.add(comment);
}
rs.close();
stmt.close();
stmt = null;
conn.close();
conn = null;
}
catch(Exception e){System.out.println( "Error --> " + displayErrorForWeb(e));}
finally {
if (stmt != null) {
try {
stmt.close();
} catch (SQLException sqlex) {
System.out.println( "Error --> " + displayErrorForWeb(sqlex));
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (SQLException sqlex) {
System.out.println( "Error --> " + displayErrorForWeb(sqlex));
}
conn = null;
}
}
return commentList;
}
private ArrayList注释(字符串uname、字符串message、int itemId、int albumId)抛出ClassNotFoundException、SQLException{
ArrayList commentList=新的ArrayList();
连接conn=null;
conn=prepareConnection();
PreparedStatement stmt=null;
字符串sql=null;
试试{
StringBuilder sb1=新的StringBuilder(1024);
sb1.追加(“插入”).append(uname.trim()).append(“注释值(?,?)”);
字符串sql1=sb1.toString();
PreparedStatement stmt1=conn.prepareStatement(sql1);
stmt1.setString(1,uname);
stmt1.setString(2,消息);
stmt1.setInt(3,itemId);
StringBuilder sb=新的StringBuilder(1024);
附加(uname.trim())。附加(“注释”);
sql=sb.toString();
stmt=conn.prepareStatement(sql);
ResultSet rs=stmt.executeQuery();
while(rs.next()){
Commenter comment=新的Commenter();
comment.setUname(rs.getString(“uname”).trim();
setComment(rs.getString(“comment”).trim();
添加(注释);
}
rs.close();
stmt.close();
stmt=null;
康涅狄格州关闭();
conn=null;
}
catch(异常e){System.out.println(“错误-->”+displayErrorForWeb(e));}
最后{
如果(stmt!=null){
试试{
stmt.close();
}捕获(SQLException sqlex){
System.out.println(“错误-->”+displayErrorForWeb(sqlex));
}
stmt=null;
}
如果(conn!=null){
试试{
康涅狄格州关闭();
}捕获(SQLException sqlex){
System.out.println(“错误-->”+displayErrorForWeb(sqlex));
}
conn=null;
}
}
返回评论列表;
}
jquery是:
$.ajax({
type: "GET",
url: "Comments",
data:'comm='+encodeURIComponent(comm)+'&'+'data-id='+encodeURIComponent(dataid)+'&'+'data-alid='+encodeURIComponent(dataalid),
dataType: "json",
success: function( data, textStatus, jqXHR)
{
if(data.success)
{
/* $.each(data, function(i, item)
{*/
var newcommhtml = '<div id="c0'+thecid+'" class="cnew clearfix"> <section class="c-author">';
newcommhtml = newcommhtml + '<h3>Anonymous</h3>';
newcommhtml = newcommhtml + '<span class="pubdate">'+month+' '+day+', '+year+'</span> </section>';
newcommhtml = newcommhtml + '<section class="c-content">';
newcommhtml = newcommhtml + '<img src="images/green-avatar.png" alt="avatar" width="80" height="80" class="ava">';
newcommhtml = newcommhtml + '<p>'+nl2br(data.commentInfo.comment)+' '+nl2br(data.commentInfo.itemId)+'</p> </section></div>';
/*newcommhtml = newcommhtml + '<p>'+nl2br(item.commentInfo.comment)+' '+nl2br(item.commentInfo.itemId)+'</p> </section></div>';
});
*/
var thelm = "#c0"+thecid;
commwrap.append(newcommhtml);
$(thelm).hide().fadeIn('slow');
setTimeout(function() { $(thelm).addClass('green'); }, 800);
$("#comm").val("");
thecid++;
if(errorspan.html() != null) {
errorspan.remove();
}
}
},
error: function(jqXHR, textStatus, errorThrown)
{
alert("error"+errorThrown);
console.log("Something really bad happened " + textStatus);
},
});
$.ajax({
键入:“获取”,
网址:“评论”,
数据:'comm='+encodeURIComponent(comm)+'&'+'data-id='+encodeURIComponent(dataid)+'&'+'data-alid='+encodeURIComponent(dataalid),
数据类型:“json”,
成功:函数(数据、文本状态、jqXHR)
{
if(data.success)
{
/*$。每个(数据、功能(i、项)
{*/
var MHTML='';
NewcomHtml=NewcomHtml+“匿名”;
newcommhtml=newcommhtml+“”+月+“”+日+“”,“+年+”;
NewcomHtml=NewcomHtml+“”;
NewcomHtml=NewcomHtml+“”;
newcommhtml=newcommhtml+''+nl2br(data.commentInfo.comment)+''+nl2br(data.commentInfo.itemId)+'';
/*newcommhtml=newcommhtml+''+nl2br(item.commentInfo.comment)+'+nl2br(item.commentInfo.itemId)+'';
});
*/
Type collectionType = new TypeToken<Collection<Integer>>(){}.getType();
Collection<Integer> ints2 = gson.fromJson(json, collectionType);