Java 以JSON格式打印hashmap内容
我有一个hashmap，在其中我按一个人拥有的汽车的名称存储汽车列表Java 以JSON格式打印hashmap内容,java,Java,我有一个hashmap，在其中我按一个人拥有的汽车的名称存储汽车列表 Map<String,List<String>> personCarMap = new HashMap<String,List<String>>(); Map personCarMap=newhashmap（）； 键是person id，值是汽车名称列表。在值中，我还要存储购买日期。所有这些都是从数据库中获取的。如何在数据库中有两个不同列的键映射 这是我目前掌握的代码 pub
Map<String,List<String>> personCarMap = new HashMap<String,List<String>>();
Map personCarMap=newhashmap（）；
public static JSONObject fetchPersonCarInfo(String person) throws SQLException
{
Map<String,List<String>> personCarMap = new HashMap<String,List<String>>();
JSONObject jObj = new JSONObject();
Connection connection = null;
PreparedStatement statement = null;
ResultSet rs = null;
try {
connection = DriverManager.getConnection("jdbc:myDriver:myDatabase",username,password);
statement = connection.prepareStatement("select personId,car,purchase_date from carz where person = ?");
rs = statement.executeQuery();
while(rs.next()) {
List<String> carIds;
if(personCarMap.containsKey(rs.getString(carId))) {
carIds = personCarMap.get(rs.getString(personId));
} else {
carIds = new ArrayList<String>();
}
carIds.add(rs.getString(carId));
carIds.add(rs.getTimestamp(purchase_date).toString()); //This is where I have a doubt.
personCarMap.put(rs.getString(carId),carIds);
}
for(Map.Entry<String, List<String>> personCarMapEntry:personCarMap.entrySet())
{
jObj.put("personID", personCarMapEntry.getKey());
jObj.put("carID", personCarMapEntry.getValue());
}
} finally{
DatabaseFunctions.closeDBResources(null, statement, rs);
}
return jObj;
}
}
publicstaticjsonobjectfetchpersoncarinfo（stringperson）抛出SQLException
{
Map personCarMap=newhashmap（）；
JSONObject jObj=新的JSONObject（）；
连接=空；
PreparedStatement=null；
结果集rs=null；
试一试{
connection=DriverManager.getConnection（“jdbc:myDriver:myDatabase”、用户名、密码）；
声明=连接。准备声明（“从carz选择个人ID、汽车、购买日期，其中个人=？”；
rs=语句。executeQuery（）；
while（rs.next（））{
列出龋齿；
if（personCarMap.containsKey（rs.getString（carId）））{
carIds=personCarMap.get（rs.getString（personId））；
}否则{
carIds=newarraylist（）；
}
添加（rs.getString（carId））；
carIds.add（rs.getTimestamp（purchase_date.toString（））；//这就是我怀疑的地方。
personCarMap.put（rs.getString（carId），carId）；
}
对于（Map.Entry personcarmpentry:personCarMap.entrySet（））
{
put（“personID”，personcarmpentry.getKey（））；
jObj.put（“carID”，personcarmpentry.getValue（））；
}
}最后{
DatabaseFunctions.closeDBResources（null、语句、rs）；
}
返回jObj；
}
}
我希望我的JSON对象显示{personId、[carId，purchasedate]}。请建议如何让JSON数组也打印出购买日期？我看到personId和carId的输出非常清晰，但我无法确定如何添加购买日期，因此需要您的专家建议 您需要使用具有两个属性carId和purchaseDate的自定义对象列表
Map<String,List<ClassNameOfCustomObject>> personCarMap = new HashMap<String,List<ClassNameOfCustomObject>>();
Map personCarMap=newhashmap（）；
通过这种方式，您可以将purchaseDate与carId一起存储在PersonCharmap中。您需要使用具有两个属性carId和purchaseDate的自定义对象列表
Map<String,List<ClassNameOfCustomObject>> personCarMap = new HashMap<String,List<ClassNameOfCustomObject>>();
Map personCarMap=newhashmap（）；
通过这种方式，您可以将purchaseDate与carId一起存储在PersonCharmap中。您需要使用具有两个属性carId和purchaseDate的自定义对象列表
Map<String,List<ClassNameOfCustomObject>> personCarMap = new HashMap<String,List<ClassNameOfCustomObject>>();
Map personCarMap=newhashmap（）；
通过这种方式，您可以将purchaseDate与carId一起存储在PersonCharmap中。您需要使用具有两个属性carId和purchaseDate的自定义对象列表
Map<String,List<ClassNameOfCustomObject>> personCarMap = new HashMap<String,List<ClassNameOfCustomObject>>();
Map personCarMap=newhashmap（）；
这样，您就可以将purchaseDate和carId一起存储在PersonCharmap中。我建议直接使用
JSONObjectpublic static JSONObject fetchPersonCarInfo(String person) throws SQLException
{
JSONObject jObj = new JSONObject();
PreparedStatement statement = null;
ResultSet rs = null;
try {
Connection connection = DriverManager.getConnection("jdbc:myDriver:myDatabase",username,password);
statement = connection.prepareStatement("SELECT personId, car, purchase_date FROM carz WHERE person = ?");
statement.setString(1, person);
rs = statement.executeQuery();
while(rs.next()) {
jObject.put("personId", rs.getString("personId");
JSONObject purchase = new JSONObject();
// there is no column with name carId in above query.
purchase.put("carId", rs.getString("car");
purchase.put("purchasedate", rs.getTimestamp("purchase_date").toString());
jObject.append("purchases", purchase);
}
} finally{
DatabaseFunctions.closeDBResources(null, statement, rs);
}
return jObj;
}
{
"personId": "ABC123",
"purchases": [
{"carId": "abc123", "purchasedate": "2013-01-01 00:00:00"},
{"carId": "def456", "purchasedate": "2013-01-02 00:00:00"}
]
}
理解JSON的外观有点困难，但我认为就是这样。无论如何，这个JSON结构对于您的数据来说是一个很好的结构。我建议直接使用
JSONObjectpublic static JSONObject fetchPersonCarInfo(String person) throws SQLException
{
JSONObject jObj = new JSONObject();
PreparedStatement statement = null;
ResultSet rs = null;
try {
Connection connection = DriverManager.getConnection("jdbc:myDriver:myDatabase",username,password);
statement = connection.prepareStatement("SELECT personId, car, purchase_date FROM carz WHERE person = ?");
statement.setString(1, person);
rs = statement.executeQuery();
while(rs.next()) {
jObject.put("personId", rs.getString("personId");
JSONObject purchase = new JSONObject();
// there is no column with name carId in above query.
purchase.put("carId", rs.getString("car");
purchase.put("purchasedate", rs.getTimestamp("purchase_date").toString());
jObject.append("purchases", purchase);
}
} finally{
DatabaseFunctions.closeDBResources(null, statement, rs);
}
return jObj;
}
{
"personId": "ABC123",
"purchases": [
{"carId": "abc123", "purchasedate": "2013-01-01 00:00:00"},
{"carId": "def456", "purchasedate": "2013-01-02 00:00:00"}
]
}
理解JSON的外观有点困难，但我认为就是这样。无论如何，这个JSON结构对于您的数据来说是一个很好的结构。我建议直接使用
JSONObjectpublic static JSONObject fetchPersonCarInfo(String person) throws SQLException
{
JSONObject jObj = new JSONObject();
PreparedStatement statement = null;
ResultSet rs = null;
try {
Connection connection = DriverManager.getConnection("jdbc:myDriver:myDatabase",username,password);
statement = connection.prepareStatement("SELECT personId, car, purchase_date FROM carz WHERE person = ?");
statement.setString(1, person);
rs = statement.executeQuery();
while(rs.next()) {
jObject.put("personId", rs.getString("personId");
JSONObject purchase = new JSONObject();
// there is no column with name carId in above query.
purchase.put("carId", rs.getString("car");
purchase.put("purchasedate", rs.getTimestamp("purchase_date").toString());
jObject.append("purchases", purchase);
}
} finally{
DatabaseFunctions.closeDBResources(null, statement, rs);
}
return jObj;
}
{
"personId": "ABC123",
"purchases": [
{"carId": "abc123", "purchasedate": "2013-01-01 00:00:00"},
{"carId": "def456", "purchasedate": "2013-01-02 00:00:00"}
]
}
理解JSON的外观有点困难，但我认为就是这样。无论如何，这个JSON结构对于您的数据来说是一个很好的结构。我建议直接使用
JSONObjectpublic static JSONObject fetchPersonCarInfo(String person) throws SQLException
{
JSONObject jObj = new JSONObject();
PreparedStatement statement = null;
ResultSet rs = null;
try {
Connection connection = DriverManager.getConnection("jdbc:myDriver:myDatabase",username,password);
statement = connection.prepareStatement("SELECT personId, car, purchase_date FROM carz WHERE person = ?");
statement.setString(1, person);
rs = statement.executeQuery();
while(rs.next()) {
jObject.put("personId", rs.getString("personId");
JSONObject purchase = new JSONObject();
// there is no column with name carId in above query.
purchase.put("carId", rs.getString("car");
purchase.put("purchasedate", rs.getTimestamp("purchase_date").toString());
jObject.append("purchases", purchase);
}
} finally{
DatabaseFunctions.closeDBResources(null, statement, rs);
}
return jObj;
}
{
"personId": "ABC123",
"purchases": [
{"carId": "abc123", "purchasedate": "2013-01-01 00:00:00"},
{"carId": "def456", "purchasedate": "2013-01-02 00:00:00"}
]
}
理解JSON的外观有点困难，但我认为就是这样。无论如何，这个JSON结构对于您的数据来说是一个很好的结构。您要求的是无效的JSON。也许
{personId:[carId，purchasedate]}{personId:[carId，purchasedate]}{personId:[carId，purchasedate]}{personId:[carId，purchasedate]}