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Improve Performance with Multiple Row Inserts and Fetches with Oracle SQL Stored Procedures and Java Spring

I currently have stored procedures for Oracle SQL, version 18c, for both inserting and fetching multiple rows of data from one parent table and one child table, being called from my Java Spring Boot application. Everything works fine, but it is extremely slow, for only a few rows of data.
When only inserting 70 records between the two, it takes up to 267 seconds into empty tables. Fetching that same data back out takes about 40 seconds.
Any help would be greatly appreciated or if there is any additional information needed from me.
Below is a cut down and renamed version of my stored procedures for my parent and child tables, actual parent table has 32 columns and child has 11.
PROCEDURE processParentData(
i_field_one varchar2,
v_parent_id OUT number) is
v_new PARENT%ROWTYPE;
BEGIN
v_new.id := ROW_SEQUENCE.nextval;
v_new.insert_time := systimestamp;
v_new.field_one := i_field_one;
insert into PARENT values v_new;
v_parent_id := v_new.id;
END;
PROCEDURE readParentData(
i_field_one IN varchar2,
v_parent OUT SYS_REFCURSOR) AS
BEGIN
OPEN v_parent FOR select h.* from PARENT h
where h.field_one = i_field_one;
END;
PROCEDURE processChild(
i_field_one varchar2,
i_parent_id number) is
v_new CHILD%ROWTYPE;
BEGIN
v_new.id := ROW_SEQUENCE.nextval;
v_new.insert_time := systimestamp;
v_new.field_one := i_field_one;
v_new.parent_id := i_parent_id;
insert into CHILD values v_new;
END;
PROCEDURE readChild(
i_parent_id IN number,
v_child OUT SYS_REFCURSOR) AS
BEGIN
OPEN v_child FOR select h.* from CHILD h
where h.parent_id = i_parent_id;
END;
For my Java code I am using Spring JDBC. After I get the parent data, I then fetch each child data by looping through the parent data and calling readChild with the parent ID for each.
var simpleJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("PARENT_PACKAGE")
.withProcedureName("processParentData");
SqlParameterSource sqlParameterSource = new MapSqlParameterSource()
.addValue("i_field_one", locationId)
.addValue("v_parent_id", null);
Map<String, Object> out = simpleJdbcCall.execute(sqlParameterSource);
var stopId = (BigDecimal) out.get("v_parent_id");
return stopId.longValue();
var simpleJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("PARENT_PACKAGE")
.withProcedureName("readParentData")
.returningResultSet("v_parent", BeanPropertyRowMapper.newInstance(Parent.class));
SqlParameterSource sqlParameterSource = new MapSqlParameterSource()
.addValue("i_field_one", location.getId());
Map<String, Object> out = simpleJdbcCall.execute(sqlParameterSource);
return (List<Parent>) out.get("v_parent");
UPDATE 1: As I know and have tested, using the same data and tables, if I use pure JDBC or JPA/Hibernate for inserting and fetching to the tables directly and avoid using stored procedures, then the whole process of inserting and fetching only takes a few seconds.
The issue is, at the company I work at, they have set a policy that all applications going forward are not allowed to have direct read/write access to the database and everything must be done through stored procedures, they say for security reasons. Meaning I need to workout how to do the same thing we have been doing for years with direct read/write access, now with only using Oracle stored procedures.
UPDATE 2: Adding my current Java code for fetching the child data.
for (Parent parent : parents) {
parent.setChilds(childRepository.readChildByParentId(parent.getId()));
}
public List<Child> readChildByParentId(long parentId) {
var simpleJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("CHILD_PACKAGE")
.withProcedureName("readChild")
.returningResultSet("v_child", BeanPropertyRowMapper.newInstance(Child.class));
SqlParameterSource sqlParameterSource = new MapSqlParameterSource()
.addValue("i_parent_id ", parentId);
Map<String, Object> out = simpleJdbcCall.execute(sqlParameterSource);
return (List<Child>) out.get("v_child");
}

The problem is that the insert you are trying to perform using the stored procedure is not optimized, because you are calling the database every time you try to insert a row.
I strongly recommend you to transform the data to XML (for example, you can also use CSV) and pass it to the procedure, then loop over it and perform the inserts that you need.
Here is an example made using Oracle:
CREATE OR REPLACE PROCEDURE MY_SCHEMA.my_procedure(xmlData clob) IS
begin
FOR CONTACT IN (SELECT *
FROM XMLTABLE(
'/CONTACTS/CONTACT' PASSING
XMLTYPE(contactes)
COLUMNS param_id FOR ORDINALITY
,id NUMBER PATH 'ID'
,name VARCHAR2(100) PATH 'NAME'
,surname VARCHAR2(100) PATH 'SURNAME'
))
LOOP
INSERT INTO PARENT_TABLE VALUES CONTACT.id, CONTACT.name, CONTACT.surname;
end loop;
end;
The XML, you can use a String to pass the data to the procedure:
<CONTACTS>
<CONTACT>
<ID>1</ID>
<NAME>Jonh</NAME>
<SURNAME>Smith</SURNAME>
</CONTACT>
<CONTACTS>

For my Java code I am using Spring JDBC. After I get the parent data, I then fetch each child data by looping through the parent data and calling readChild with the parent ID for each.
Instead of fetching child data in loop, you can modify your procedure to accept list of parent id and return all the data in one call.
It will be helpful if you share spring boot for loop code as well.
Update
Instead of fetching single parent details, you should have update your code like this. Also you have to update your procedure as well.
List<Long> parents = new ArrayList<>();
for (Parent parent : parents) {
parents.add(parent.getId());
}
You can use java streams but that is secondary things.
Now you have to modify your procedure and method to accept multiple parent ids.
List<Child> children = childRepository.readreadChildByParentId(parents);
public List<Child> readChildByParentId(long parentId) {
var simpleJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("CHILD_PACKAGE")
.withProcedureName("readChild")
.returningResultSet("v_child", BeanPropertyRowMapper.newInstance(Child.class));
SqlParameterSource sqlParameterSource = new MapSqlParameterSource()
.addValue("i_parent_id ", parentId);
Map<String, Object> out = simpleJdbcCall.execute(sqlParameterSource);
return (List<Child>) out.get("v_child");
}
After having all the children you can set parent children via java code.
P.S.
Could you please check if you fetch parents with children if parent is coming from the database?

Your performance problems are probably related with the number of operations performed against the database: you are iterating in Java your collections, and interacting with the database in every iteration. You need to minimize the number of operations performed.
One possible solution can be the use of the standard STRUCT and ARRAY Oracle types. Please, consider for instance the following example:
public static void insertData() throws SQLException {
DriverManagerDataSource dataSource = ...
JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
jdbcTemplate.setResultsMapCaseInsensitive(true);
SimpleJdbcCall insertDataCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("parent_child_pkg")
.withProcedureName("insert_data")
.withoutProcedureColumnMetaDataAccess()
.useInParameterNames("p_parents")
.declareParameters(
new SqlParameter("p_parents", OracleTypes.ARRAY, "PARENT_ARRAY")
);
OracleConnection connection = null;
try {
connection = insertDataCall
.getJdbcTemplate()
.getDataSource()
.getConnection()
.unwrap(OracleConnection.class)
;
List<Parent> parents = new ArrayList<>(100);
Parent parent = null;
List<Child> chilren = null;
Child child = null;
for (int i = 0; i < 100; i++) {
parent = new Parent();
parents.add(parent);
parent.setId((long) i);
parent.setName("parent-" + i);
chilren = new ArrayList<>(1000);
parent.setChildren(chilren);
for (int j = 0; j < 1000; j++) {
child = new Child();
chilren.add(child);
child.setId((long) j);
child.setName("parent-" + j);
}
}
System.out.println("Inserting data...");
StopWatch stopWatch = new StopWatch();
stopWatch.start("insert-data");
StructDescriptor parentTypeStructDescriptor = StructDescriptor.createDescriptor("PARENT_TYPE", connection);
ArrayDescriptor parentArrayDescriptor = ArrayDescriptor.createDescriptor("PARENT_ARRAY", connection);
StructDescriptor childTypeStructDescriptor = StructDescriptor.createDescriptor("CHILD_TYPE", connection);
ArrayDescriptor childArrayDescriptor = ArrayDescriptor.createDescriptor("CHILD_ARRAY", connection);
Object[] parentArray = new Object[parents.size()];
int pi = 0;
for (Parent p : parents) {
List<Child> children = p.getChildren();
Object[] childArray = new Object[children.size()];
int ci = 0;
for (Child c : children) {
Object[] childrenObj = new Object[2];
childrenObj[0] = c.getId();
childrenObj[1] = c.getName();
STRUCT childStruct = new STRUCT(childTypeStructDescriptor, connection, childrenObj);
childArray[ci++] = childStruct;
}
ARRAY childrenARRAY = new ARRAY(childArrayDescriptor, connection, childArray);
Object[] parentObj = new Object[3];
parentObj[0] = p.getId();
parentObj[1] = p.getName();
parentObj[2] = childrenARRAY;
STRUCT parentStruct = new STRUCT(parentTypeStructDescriptor, connection, parentObj);
parentArray[pi++] = parentStruct;
}
ARRAY parentARRAY = new ARRAY(parentArrayDescriptor, connection, parentArray);
Map in = Collections.singletonMap("p_parents", parentARRAY);
insertDataCall.execute(in);
connection.commit();
stopWatch.stop();
System.out.println(stopWatch.prettyPrint());
} catch (Throwable t) {
t.printStackTrace();
connection.rollback();
} finally {
if (connection != null) {
try {
connection.close();
} catch (Throwable nested) {
nested.printStackTrace();
}
}
}
}
Where:
CREATE OR REPLACE TYPE child_type AS OBJECT (
id NUMBER,
name VARCHAR2(512)
);
CREATE OR REPLACE TYPE child_array
AS TABLE OF child_type;
CREATE OR REPLACE TYPE parent_type AS OBJECT (
id NUMBER,
name VARCHAR2(512),
children child_array
);
CREATE OR REPLACE TYPE parent_array
AS TABLE OF parent_type;
CREATE SEQUENCE PARENT_SEQ INCREMENT BY 1 MINVALUE 1;
CREATE SEQUENCE CHILD_SEQ INCREMENT BY 1 MINVALUE 1;
CREATE TABLE parent_table (
id NUMBER,
name VARCHAR2(512)
);
CREATE TABLE child_table (
id NUMBER,
name VARCHAR2(512),
parent_id NUMBER
);
CREATE OR REPLACE PACKAGE parent_child_pkg AS
PROCEDURE insert_data(p_parents PARENT_ARRAY);
END;
CREATE OR REPLACE PACKAGE BODY parent_child_pkg AS
PROCEDURE insert_data(p_parents PARENT_ARRAY) IS
l_parent_id NUMBER;
l_child_id NUMBER;
BEGIN
FOR i IN 1..p_parents.COUNT LOOP
SELECT parent_seq.nextval INTO l_parent_id FROM dual;
INSERT INTO parent_table(id, name)
VALUES(l_parent_id, p_parents(i).name);
FOR j IN 1..p_parents(i).children.COUNT LOOP
SELECT child_seq.nextval INTO l_child_id FROM dual;
INSERT INTO child_table(id, name, parent_id)
VALUES(l_child_id, p_parents(i).name, l_parent_id);
END LOOP;
END LOOP;
END;
END;
And Parent and Child are simple POJOs:
import java.util.ArrayList;
import java.util.List;
public class Parent {
private Long id;
private String name;
private List<Child> children = new ArrayList<>();
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Child> getChildren() {
return children;
}
public void setChildren(List<Child> children) {
this.children = children;
}
}
public class Child {
private Long id;
private String name;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Please, forgive for the code legibility and incorrect error handling, I will improve the answer later including some information about obtaining the data as well.

The times you mention are horrible indeed. A big boost forward in performance will be to work set based. This means reducing the row by row database calls.
Row by row is synonymous for slow, especially when network round trips are involved.
One call to get the parent.
One call to get the set of children and process them. The jdbc fetch size is a nice tunable here. Give it a chance to work for you.

You do not need to use DYNAMIC SQL OPEN v_parent FOR and also it is not clear how the view v_parent is defined.
Try to check exec plan of this query:
FOR select h.* from PARENT h where h.field_one = ?;
Usually returning recordset via SYS_REFCURSOR increases performance when you return more (let's say) than 10K records.

The SimpleJdbcCall object can be reused in your scenario as only the parameters changes. The SimpleJdbcCall object compiles the jdbc statement on the first invocation. It does some meta-data fetching and it interacts with the Database for that. So, having separate objects would mean fetching same metadata that many times which is not needed.
So, I suggest to initialise all the 4 SimpleJdbcCall objects in the very beginning and then work with them.
var insertParentJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("PARENT_PACKAGE")
.withProcedureName("processParentData");
var readParentJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("PARENT_PACKAGE")
.withProcedureName("readParentData")
.returningResultSet("v_parent", BeanPropertyRowMapper.newInstance(Parent.class));
var insertChildJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("CHILD_PACKAGE")
.withProcedureName("processChildData");
var readChildJdbcCall = new SimpleJdbcCall(jdbcTemplate)
.withCatalogName("CHILD_PACKAGE")
.withProcedureName("readChild")
.returningResultSet("v_child", BeanPropertyRowMapper.newInstance(Child.class));

RavenDB query returns null

I'm on RavenDB 3.5.35183. I have a type:
import com.mysema.query.annotations.QueryEntity;
#QueryEntity
public class CountryLayerCount
{
public String countryName;
public int layerCount;
}
and the following query:
private int getCountryLayerCount(String countryName, IDocumentSession currentSession)
{
QCountryLayerCount countryLayerCountSurrogate = QCountryLayerCount.countryLayerCount;
IRavenQueryable<CountryLayerCount> levelDepthQuery = currentSession.query(CountryLayerCount.class, "CountryLayerCount/ByName").where(countryLayerCountSurrogate.countryName.eq(countryName));
CountryLayerCount countryLayerCount = new CountryLayerCount();
try (CloseableIterator<StreamResult<CountryLayerCount>> results = currentSession.advanced().stream(levelDepthQuery))
{
while(results.hasNext())
{
StreamResult<CountryLayerCount> srclc = results.next();
System.out.println(srclc.getKey());
CountryLayerCount clc = srclc.getDocument();
countryLayerCount = clc;
break;
}
}
catch(Exception e)
{
}
return countryLayerCount.layerCount;
}
The query executes successfully, and shows the correct ID for the document I'm retrieving (e.g. "CountryLayerCount/123"), but its data members are both null. The where clause also works fine, the country name is used to retrieve individual countries. This is so simple, but I can't see where I've gone wrong. The StreamResult contains the correct key, but getDocument() doesn't work - or, rather, it doesn't contain an object. The collection has string IDs.
In the db logger, I can see the request coming in:
Receive Request # 29: GET - geodata - http://localhost:8888/databases/geodata/streams/query/CountryLayerCount/ByName?&query=CountryName:Germany
Request # 29: GET - 22 ms - geodata - 200 - http://localhost:8888/databases/geodata/streams/query/CountryLayerCount/ByName?&query=CountryName:Germany
which, when plugged into the browser, correctly gives me:
{"Results":[{"countryName":"Germany","layerCount":5,"#metadata":{"Raven-Entity-Name":"CountryLayerCounts","Raven-Clr-Type":"DbUtilityFunctions.CountryLayerCount, DbUtilityFunctions","#id":"CountryLayerCounts/212","Temp-Index-Score":0.0,"Last-Modified":"2018-02-03T09:41:36.3165473Z","Raven-Last-Modified":"2018-02-03T09:41:36.3165473","#etag":"01000000-0000-008B-0000-0000000000D7","SerializedSizeOnDisk":164}}
]}
The index definition:
from country in docs.CountryLayerCounts
select new {
CountryName = country.countryName
}
AFAIK, one doesn't have to index all the fields of the object to retrieve it in its entirety, right ? In other words, I just need to index the field(s) to find the object, not all the fields I want to retrieve; at least that was my understanding...
Thanks !

The problem is related to incorrect casing.
For example:
try (IDocumentSession sesion = store.openSession()) {
CountryLayerCount c1 = new CountryLayerCount();
c1.layerCount = 5;
c1.countryName = "Germany";
sesion.store(c1);
sesion.saveChanges();
}
Is saved as:
{
"LayerCount": 5,
"CountryName": "Germany"
}
Please notice we use upper case letters in json for property names (this only applies to 3.X versions).
So in order to make it work, please update json properties names + edit your index:
from country in docs.CountryLayerCounts
select new {
CountryName = country.CountryName
}
Btw. If you have per country aggregation, then you can simply query using:
QCountryLayerCount countryLayerCountSurrogate =
QCountryLayerCount.countryLayerCount;
CountryLayerCount levelDepthQuery = currentSession
.query(CountryLayerCount.class, "CountryLayerCount/ByName")
.where(countryLayerCountSurrogate.countryName.eq(countryName))
.single();

Call graphs in Soot

How do I use SOOT to build at Call graph? Or are there any better programs for this? I have been sent around the same five pages looking for answers and I can't find what I am looking for. There are also a problem with the plugin version to Eclipse. It is installed correct but I cant choose it when I want to run the code.

Small modification to previous answer
private static void visit(CallGraph cg, SootMethod method) {
String identifier = method.getSignature();
visited.put(method.getSignature(), true);
dot.drawNode(identifier);
// iterate over unvisited parents
Iterator<MethodOrMethodContext> ptargets = new Sources(cg.edgesInto(method));
if (ptargets != null) {
while (ptargets.hasNext()) {
SootMethod parent = (SootMethod) ptargets.next();
if (!visited.containsKey(parent.getSignature())) visit(cg, parent);
}
}

Here are some examples include call graph for Java. http://www.brics.dk/SootGuide/
And call graph for apk.
https://github.com/secure-software-engineering/soot-infoflow/issues/38
If you want to get the dot file, you can iterate over the callgraph and write the contents out in dot format like this.
private static void visit(CallGraph cg, SootMethod method) {
String identifier = method.getSignature();
visited.put(method.getSignature(), true);
dot.drawNode(identifier);
// iterate over unvisited parents
Iterator<MethodOrMethodContext> ptargets = new Targets(cg.edgesInto(method));
if (ptargets != null) {
while (ptargets.hasNext()) {
SootMethod parent = (SootMethod) ptargets.next();
if (!visited.containsKey(parent.getSignature())) visit(cg, parent);
}
}
// iterate over unvisited children
Iterator<MethodOrMethodContext> ctargets = new Targets(cg.edgesOutOf(method));
if (ctargets != null) {
while (ctargets.hasNext()) {
SootMethod child = (SootMethod) ctargets.next();
dot.drawEdge(identifier, child.getSignature());
System.out.println(method + " may call " + child);
if (!visited.containsKey(child.getSignature())) visit(cg, child);
}
}
}

Javax JCR Node getProperties and Titles

I am given a Node and I then request form it another Node.
Node nn = node.getNode("jcr:content");
From here I can do the following to get the value of
nn.getProperty("cq:lastModified")
What I am trying to do is get all the properties without asking for each one by name.
Node nn = node.getNode("jcr:content");
PropertyIterator pi = nn.getProperties();
Now I can iterate over the properties and print their values as so:
while(pi.hasNext())
{
Property p = pi.nextProperty();
String val = p.getString();
}
But how can I find the title of this Property?

I am not sure but you can try getName() method because Property interface is subinterface of Item interface. You can try like below :
while(pi.hasNext())
{
Property p = pi.nextProperty();
String name = p.getName();
String val = p.getString();
}

Get Xpath from the org.w3c.dom.Node

Can i get the full xpath from the org.w3c.dom.Node ?
Say currently node is pointing to some where the middle of the xml document. I would like extract the xpath for that element.
The output xpath I'm looking for is //parent/child1/chiild2/child3/node. A parent to node xpath. Just ignore the xpath's which are having expressions and points to the same node.

There's no generic method for getting the XPath, mainly because there's no one generic XPath that identifies a particular node in the document. In some schemas, nodes will be uniquely identified by an attribute (id and name are probably the most common attributes.) In others, the name of each element (that is, the tag) is enough to uniquely identify a node. In a few (unlikely, but possible) cases, there's no one unique name or attribute that takes you to a specific node, and so you'd need to use cardinality (get the n'th child of the m'th child of...).
EDIT:
In most cases, it's not hard to create a schema-dependent function to assemble an XPath for a given node. For example, suppose you have a document where every node is uniquely identified by an id attribute, and you're not using namespaces. Then (I think) the following pseudo-Java would work to return an XPath based on those attributes. (Warning: I have not tested this.)
String getXPath(Node node)
{
Node parent = node.getParent();
if (parent == null) {
return "/" + node.getTagName();
}
return getXPath(parent) + "/" + "[#id='" + node.getAttribute("id") + "']";
}

I am working for the company behind jOOX, a library that provides many useful extensions to the Java standard DOM API, mimicking the jquery API. With jOOX, you can obtain the XPath of any element like this:
String path = $(element).xpath();
The above path will then be something like this
/document[1]/library[2]/books[3]/book[1]

I've taken this code from
Mikkel Flindt post & modified it so it can work for Attribute Node.
public static String getFullXPath(Node n) {
// abort early
if (null == n)
return null;
// declarations
Node parent = null;
Stack<Node> hierarchy = new Stack<Node>();
StringBuffer buffer = new StringBuffer();
// push element on stack
hierarchy.push(n);
switch (n.getNodeType()) {
case Node.ATTRIBUTE_NODE:
parent = ((Attr) n).getOwnerElement();
break;
case Node.ELEMENT_NODE:
parent = n.getParentNode();
break;
case Node.DOCUMENT_NODE:
parent = n.getParentNode();
break;
default:
throw new IllegalStateException("Unexpected Node type" + n.getNodeType());
}
while (null != parent && parent.getNodeType() != Node.DOCUMENT_NODE) {
// push on stack
hierarchy.push(parent);
// get parent of parent
parent = parent.getParentNode();
}
// construct xpath
Object obj = null;
while (!hierarchy.isEmpty() && null != (obj = hierarchy.pop())) {
Node node = (Node) obj;
boolean handled = false;
if (node.getNodeType() == Node.ELEMENT_NODE) {
Element e = (Element) node;
// is this the root element?
if (buffer.length() == 0) {
// root element - simply append element name
buffer.append(node.getNodeName());
} else {
// child element - append slash and element name
buffer.append("/");
buffer.append(node.getNodeName());
if (node.hasAttributes()) {
// see if the element has a name or id attribute
if (e.hasAttribute("id")) {
// id attribute found - use that
buffer.append("[#id='" + e.getAttribute("id") + "']");
handled = true;
} else if (e.hasAttribute("name")) {
// name attribute found - use that
buffer.append("[#name='" + e.getAttribute("name") + "']");
handled = true;
}
}
if (!handled) {
// no known attribute we could use - get sibling index
int prev_siblings = 1;
Node prev_sibling = node.getPreviousSibling();
while (null != prev_sibling) {
if (prev_sibling.getNodeType() == node.getNodeType()) {
if (prev_sibling.getNodeName().equalsIgnoreCase(
node.getNodeName())) {
prev_siblings++;
}
}
prev_sibling = prev_sibling.getPreviousSibling();
}
buffer.append("[" + prev_siblings + "]");
}
}
} else if (node.getNodeType() == Node.ATTRIBUTE_NODE) {
buffer.append("/#");
buffer.append(node.getNodeName());
}
}
// return buffer
return buffer.toString();
}

For me this one worked best ( using org.w3c.dom elements):
String getXPath(Node node)
{
Node parent = node.getParentNode();
if (parent == null)
{
return "";
}
return getXPath(parent) + "/" + node.getNodeName();
}

Some IDEs specialised in XML will do that for you.
Here are the most well known
oXygen
Stylus Studio
xmlSpy
For instance in oXygen, you can right-click on an element part of an XML document and the contextual menu will have an option 'Copy Xpath'.
There are also a number of Firefox add-ons (such as XPather that will happily do the job for you. For Xpather, you just click on a part of the web page and select in the contextual menu 'show in XPather' and you're done.
But, as Dan has pointed out in his answer, the XPath expression will be of limited use. It will not include predicates for instance. Rather it will look like this.
/root/nodeB[2]/subnodeX[2]
For a document like
<root>
<nodeA>stuff</nodeA>
<nodeB>more stuff</nodeB>
<nodeB cond="thisOne">
<subnodeX>useless stuff</subnodeX>
<subnodeX id="MyCondition">THE STUFF YOU WANT</subnodeX>
<subnodeX>more useless stuff</subnodeX>
</nodeB>
</root>
The tools I listed will not generate
/root/nodeB[#cond='thisOne']/subnodeX[#id='MyCondition']
For instance for an html page, you'll end-up with the pretty useless expression :
/html/body/div[6]/p[3]
And that's to be expected. If they had to generate predicates, how would they know which condition is relevant ? There are zillions of possibilities.

Something like this will give you a simple xpath:
public String getXPath(Node node) {
return getXPath(node, "");
}
public String getXPath(Node node, String xpath) {
if (node == null) {
return "";
}
String elementName = "";
if (node instanceof Element) {
elementName = ((Element) node).getLocalName();
}
Node parent = node.getParentNode();
if (parent == null) {
return xpath;
}
return getXPath(parent, "/" + elementName + xpath);
}