I receive a list of models. The number of models could be large. This models has a bunch of properties and any of them could be null potentially.
I need to build a string for every model based of it's properties. If property == null then I add some static part to the result string like "property1 is null".
If else property != null then I add something like this "property1 == 'valueOfThePropertyHere'".
The result string should look something like this:
prop1 == 'value1' and prop2 is null and prop3 == 'value3' and prop4 == 'value4' and prop5 is null and ..... propN == 'valueN'
And I generate such string for every model from the list.
Obviously I do this in for loop and I use StringBuilder for this. The thing is that in append method of StringBuilder I check every field of the model for null using ternary operator and based on this I add the result of this check to the result string. But if a property is not null then I need to add some static part + value of the field itself + some more static stuff. And that means I need to add one more StringBuilder for every property I have. Or I can use '+' which will be transformed into StringBuilder anyway and as far as I know it's a bad practise to use '+' inside StringBuilder (but I have to use it anyway).
Example:
List<Model> models = repository.getModels();
for (Model m: models) {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder
.append(m.getField1() == null ? "field1 is null" : "field1 == '" + new StringBuiler().append(m.getField1()).append("'").append(" and ").toString()))
.append(m.getField2() == null ? "field2 is null" : "field2 == '" + new StringBuiler().append(m.getField2()).append("'").append(" and ").toString()))
...............
.append(m.getFieldN() == null ? "fieldN is null" : "fieldN == '" + new StringBuiler().append(m.getFieldN()).append("'").append(" and ").toString()));
System.out.println(stringBuilder.toString());
}
In my opinion from the performance perspective it doesn't look so well because for every model from a list of models I create another bunch of StringBuilder objects in heap just to get the result string.
Am I missing something? Are there better ways to do so from the performance perspective? Or it's okay because I don't see other options for now.
Go for simple.
Instead of
stringBuilder
.append(m.getField1() == null ? "field1 is null" : "field1 == '" + new StringBuiler().append(m.getField1()).append("'").append(" and ").toString()))
use:
if (m.getField1() == null) {
stringBuilder.append("field1 is null");
} else {
stringBuilder.append("field1 == '").append(m.getField1()).append("'").append(" and ");
}
Aside from the distinct oddness of using a StringBuilder inside a StringBuilder.append call (and why not just use + anyway...), it's really hard to parse where the : is in the conditional expression. Breaking it into lines is much easier.
If you find yourself having to repeat this code pattern a lot, define a method:
void append(StringBuilder stringBuilder, String name, Object value) {
stringBuilder.append(name);
if (value == null) {
stringBuilder.append(" is null");
} else {
stringBuilder.append(" == '").append(value).append("'").append(" and ");
}
}
and then invoke like:
append(stringBuilder, "field1", m.getField1());
append(stringBuilder, "field2", m.getField2());
append(stringBuilder, "field3", m.getField3());
What a mess! Just because you can chain invocations, doesn't mean you should:
List<Model> models = repository.getModels();
for (Model m: models) {
StringBuilder stringBuilder = new StringBuilder();
String field = m.getField1();
if(field==null) {
stringBuilder.append("field1 is null");
} else {
stringBuilder.append("field1 == ").append(m.getField1()).append("'");
}
if(stringBuilder.length()>0) {
stringBuilder.append(" and ");
}
field = m.getField2();
if(field==null) {
stringBuilder.append("field2 is null");
} else {
stringBuilder.append("field2 == ").append(m.getField1()).append("'");
}
if(stringBuilder.length()>0) {
stringBuilder.append(" and ");
}
...
System.out.println(stringBuilder.toString());
}
To avoid all this potential repetition (depending on number of fields):
void appendField(StringBuilder stringBuilder, String fieldName, String value) {
if(stringBuilder.length()>0) {
stringBuilder.append(" and ");
}
stringBuilder.append(fieldName);
if(value==null) {
stringBuilder.append(" is null");
} else {
stringBuilder.append(" == '").append(value).append("'");
}
}
String toString(Model m) {
StringBuilder stringBuilder = new StringBuilder();
appendField(stringBuilder, "field1", m.getField1());
appendField(stringBuilder, "field2", m.getField2());
...
appendField(stringBuilder, "fieldN", m.getFieldN());
return stringBuilder.toString();
}
List<Model> models = repository.getModels();
for (Model m: models) {
System.out.println(toString(m));
}
Related
I am new to Java and practicing parsing csv file into the object. I've tried but cannot figure it out.
The file looks like this:
[0], [1], [2], [3] , [4] , [5] , [6] , [7] , [8] , [9]
class, gender, age, bodyType, profession, pregnant, isYou ,species, isPet, role
scenario:green, , , , , , , ,
person, female, 24, average , , FALSE , , , , passenger
animal, male , 4, , , FALSE , , dog , TRUE , pedestrian
scenario:red
person, male , 16, athletic, boxer , FALSE , TRUE , , , passenger
person, female, 25, athletic, doctor , TRUE , FALSE , , , pedestrian
I need to parse it by any number of passengers and pedestrians with any scenarios. Finally, add these scenarios into an ArrayList for analyzing.
What I think is to:
loop through each line, stops when reaches to the next scenario:red, adds the passengers and the pedestrians to the Character ArrayList. (I've done adding, but don't how to stop).
Create a scenario using constructor scenario(ArrayList<Character> passenger, ArrayList<Character> pedestrians, boolean redOrGreen);
The ArrayList scenarios add the created scenarios.
What I've done is put everything together instead of separate them. Any help or hint is highly appreciated.
Thanks for this community who helped me, here is what I've got so far.
public void loadCsv() throws IOException {
String csvFile = "config.csv";
String line = "";
String csvSplit = "\\s*,\\s*";
Scenario scenario = new Scenario();
Person person = new Person();
Animal animal = new Animal();
ArrayList<Scenario> scenaios = new ArrayList<Scenario>();
ArrayList<String> csvContents = new ArrayList<String>();
ArrayList<Character> passengers = new ArrayList<Character>();
ArrayList<Character> pedestrians = new ArrayList<Character>();
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of the header
//add each line to the arrayList
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);
}
for(String csvLine : csvContents) {
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
if (data.length == NO_OF_FIELD) { //check and avoid indexOutOfBoundException
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
if (clazz.startsWith("scenario") && data.length == 1) {
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
}
else if ("person".equals(clazz) && data.length ==10) {
person = loadCsvPerson(data);
addCharacter(person, data);
}
else if ("animal".equals(clazz) && data.length ==10) {
animal = loadCsvAnimal(data);
addCharacter(animal, data);
}
}
}
}
//passenger and pedestrians are in position
System.out.println("passengers: " + passengers);
System.out.println("pedestrians: " + pedestrians);
if (null != scenario) {
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
If it is possible to change the csv file format, I would add scenario type column (and scenario id or name if required), so you can work with csv file as a result set from database when you join tables (scenario + passenger + pedestrian) and return plain rows.
With this approach you will be able to delegate parsing to any csv library and do your logic (group by scenario id/name/type) separately. With surrogate rows you have (scenario:green...) you have to write your custom parser.
For example, you can use univocity to simply parse file into your model (even using annotations) and iteratively group it and handle.
Or if you need to work with existing file format do something like that:
if (clazz.startsWith("scenario") && data.length == 1) {
// collect existing scenario before starting processing new one
if (scenario != null) {
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
passengers = new ArrayList();
pedestrians = new ArrayList();
scenarios.add(scenario);
}
// now start new group (scenario)
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
}
Following things need to be addressed in your code:
Strive to avoid using the name of a class which is already used by the standard library (and especially when it is in the default package, java.lang) e.g. there is already a class Character in Java library and therefore you should use a different name for your custom class.
Use continue to skip the line, scenario:red
for(String csvLine : csvContents) {
if(csvLine.equals("scenario:red")){
continue;
}
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
if (data.length == NO_OF_FIELD) {
//..
}
//..
}
If you have already defined final int NO_OF_FIELD = 10, you can use the same instead of using the value 10 directly i.e. you should use NO_OF_FIELD instead of 10 in the following code:
if (data.length == NO_OF_FIELD) { //check and avoid indexOutOfBoundException
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
//...
else if ("person".equals(clazz) && data.length ==10) {
However, you also need to understand that && data.length ==10 is unnecessary here as you have already checked data.length == NO_OF_FIELD in the enclosing if condition.
I couldn't understand the rest of your points. If you clarify them, I'll be able to help you further.
I need to add the previous scenario in the second round.
Since the last set of data won't be captured, I need to set another new scenario to add it in. Thanks for the art sir.
Character character = null;
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of the header
//add each line to the arrayList
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);
}
final int NO_OF_FIELDS = 10;
for(String csvLine : csvContents) {
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
if (clazz.startsWith("scenario") && data.length == 1) {
// adding scenario after one set of data
// i.e second round adding the first round data
if (passengers.size() != 0 && pedestrians.size() != 0) {
Scenario scenario = new Scenario();
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
scenarios.add(scenario);
}
passengers = new ArrayList<Character>();
pedestrians = new ArrayList<Character>();
if (clazz.endsWith("green")) {
scenario.setLegalCrossing(true);
System.out.println("green light");
}
else if (clazz.endsWith("red")){
scenario.setLegalCrossing(false);
System.out.println("red light");
}
continue;
}
//...
Scenario scenario = new Scenario();
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
scenarios.add(scenario);
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
Audit audit = new Audit();
audit.setScenario(scenarios);
I'm hoping to trim all Strings that are part of an object graph.
So I have an object graph like so
RootElement
- name (String)
- adjective (String)
- items ArrayOfItems
- getItems (List<Item>)
- get(i) (Item)
Item
- name (String)
- value (double)
- alias (String)
- references ArrayOfReferences
- getReferences (List<Reference>)
- get(i) (Reference)
Reference
- prop1 (String)
- prop2 (Integer)
- prop3 (String)
There is a get and set pair for every property of every class represented in this object graph. Ideally every field of type String would end up trimmed, including enumerating any child objects contained in collections. There are no cycles contained within the object graph.
Is there any java library that implements some sort of generic object graph visitor pattern or String\Reflection utility library that does this?
An external third party library that does this would also be fine, it does not have to be part of the standard java libraries.
No, there's no built-in traversal for something like this, and remember that Java Strings are immutable, so you can't actually trim in place--you have to trim and replace. Some objects may not permit modification of their String variables.
Below is the explanation of solution that I have built using Java Reflection API. I have posted the working code (with its url to github) below. This solution mainly uses:
Java Reflection API
Independent handling of Java Collections
Recursion
To start with, I have used Introspector to go over the readMethods of the Class omitting the methods defined for Object
for (PropertyDescriptor propertyDescriptor : Introspector
.getBeanInfo(c, Object.class).getPropertyDescriptors()) {
Method method = propertyDescriptor.getReadMethod();
Cases
If the current level of Property is of type String
If its an Object Array of Properties
If its a String array
If its a type of Java Collection class
Separate placement for Map with special conditions to process its keys and values
This utility uses the Java Reflection API to traverse through an object graph with disciplined syntax of getters and setters and trims all strings encountered within an Object graph recursively.
Code
This entire util class with the main test class (and custom data types/pojos) is here on my github
Usage:
myObj = (MyObject) SpaceUtil.trimReflective(myObj);
Util method:
public static Object trimReflective(Object object) throws Exception {
if (object == null)
return null;
Class<? extends Object> c = object.getClass();
try {
// Introspector usage to pick the getters conveniently thereby
// excluding the Object getters
for (PropertyDescriptor propertyDescriptor : Introspector
.getBeanInfo(c, Object.class).getPropertyDescriptors()) {
Method method = propertyDescriptor.getReadMethod();
String name = method.getName();
// If the current level of Property is of type String
if (method.getReturnType().equals(String.class)) {
String property = (String) method.invoke(object);
if (property != null) {
Method setter = c.getMethod("set" + name.substring(3),
new Class<?>[] { String.class });
if (setter != null)
// Setter to trim and set the trimmed String value
setter.invoke(object, property.trim());
}
}
// If an Object Array of Properties - added additional check to
// avoid getBytes returning a byte[] and process
if (method.getReturnType().isArray()
&& !method.getReturnType().isPrimitive()
&& !method.getReturnType().equals(String[].class)
&& !method.getReturnType().equals(byte[].class)) {
System.out.println(method.getReturnType());
// Type check for primitive arrays (would fail typecasting
// in case of int[], char[] etc)
if (method.invoke(object) instanceof Object[]) {
Object[] objectArray = (Object[]) method.invoke(object);
if (objectArray != null) {
for (Object obj : (Object[]) objectArray) {
// Recursively revisit with the current property
trimReflective(obj);
}
}
}
}
// If a String array
if (method.getReturnType().equals(String[].class)) {
String[] propertyArray = (String[]) method.invoke(object);
if (propertyArray != null) {
Method setter = c.getMethod("set" + name.substring(3),
new Class<?>[] { String[].class });
if (setter != null) {
String[] modifiedArray = new String[propertyArray.length];
for (int i = 0; i < propertyArray.length; i++)
if (propertyArray[i] != null)
modifiedArray[i] = propertyArray[i].trim();
// Explicit wrapping
setter.invoke(object,
new Object[] { modifiedArray });
}
}
}
// Collections start
if (Collection.class.isAssignableFrom(method.getReturnType())) {
Collection collectionProperty = (Collection) method
.invoke(object);
if (collectionProperty != null) {
for (int index = 0; index < collectionProperty.size(); index++) {
if (collectionProperty.toArray()[index] instanceof String) {
String element = (String) collectionProperty
.toArray()[index];
if (element != null) {
// Check if List was created with
// Arrays.asList (non-resizable Array)
if (collectionProperty instanceof List) {
((List) collectionProperty).set(index,
element.trim());
} else {
collectionProperty.remove(element);
collectionProperty.add(element.trim());
}
}
} else {
// Recursively revisit with the current property
trimReflective(collectionProperty.toArray()[index]);
}
}
}
}
// Separate placement for Map with special conditions to process
// keys and values
if (method.getReturnType().equals(Map.class)) {
Map mapProperty = (Map) method.invoke(object);
if (mapProperty != null) {
// Keys
for (int index = 0; index < mapProperty.keySet().size(); index++) {
if (mapProperty.keySet().toArray()[index] instanceof String) {
String element = (String) mapProperty.keySet()
.toArray()[index];
if (element != null) {
mapProperty.put(element.trim(),
mapProperty.get(element));
mapProperty.remove(element);
}
} else {
// Recursively revisit with the current property
trimReflective(mapProperty.get(index));
}
}
// Values
for (Map.Entry entry : (Set<Map.Entry>) mapProperty
.entrySet()) {
if (entry.getValue() instanceof String) {
String element = (String) entry.getValue();
if (element != null) {
entry.setValue(element.trim());
}
} else {
// Recursively revisit with the current property
trimReflective(entry.getValue());
}
}
}
} else {// Catch a custom data type as property and send through
// recursion
Object property = (Object) method.invoke(object);
if (property != null) {
trimReflective(property);
}
}
}
} catch (Exception e) {
throw new Exception("Strings cannot be trimmed because: ", e);
}
return object;
}
Test
I also have a test class in there which creates a relatively complex object. The test class has different scenarios that cover:
String properties
Properties as custom datatypes which in turn have String properties
Properties as custom datatypes which in turn have properties as custom datatypes which in turn have String properties
List of custom data types
Set of Strings
Array of custom data types
Array of Strings
Map of String and custom data type
Object Graph:
Test Object Code Snippet:
public static Music buildObj() {
Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Artist artist1 = new Artist();
Artist artist2 = new Artist();
song1.setGenre("ROCK ");
song1.setSonnet("X ");
song1.setNotes("Y ");
song1.setCompostions(Arrays.asList(new String[] { "SOME X DATA ",
"SOME OTHER DATA X ", "SOME MORE DATA X ", " " }));
Set<String> instruments = new HashSet<String>();
instruments.add(" GUITAR ");
instruments.add(" SITAR ");
instruments.add(" DRUMS ");
instruments.add(" BASS ");
song1.setInstruments(instruments);
song2.setGenre("METAL ");
song2.setSonnet("A ");
song2.setNotes("B ");
song2.setCompostions(Arrays.asList(new String[] { "SOME Y DATA ",
" SOME OTHER DATA Y ",
" SOME MORE DATA Y ", " " }));
song3.setGenre("POP ");
song3.setSonnet("DONT ");
song3.setNotes("KNOW ");
song3.setCompostions(Arrays.asList(new String[] { "SOME Z DATA ",
" SOME OTHER DATA Z ",
" SOME MORE DATA Z ", " " }));
artist1.setSongList(Arrays.asList(new Song[] { song1, song3 }));
artist2.setSongList(Arrays.asList(new Song[] { song1, song2, song3 }));
Map<String, Person> artistMap = new HashMap<String, Person>();
Person tutor1 = new Person();
tutor1.setName("JOHN JACKSON DOE ");
artistMap.put(" Name ", tutor1);
Person coach1 = new Person();
coach1.setName("CARTER ");
artistMap.put("Coach ", coach1);
artist2.setTutor(artistMap);
music.setSongs(Arrays.asList(new Song[] { song1, song2, song3 }));
music.setArtists(Arrays.asList(new Artist[] { artist1, artist2 }));
music.setLanguages(new String[] { " ENGLISH ", "FRENCH ",
"HINDI " });
Person singer1 = new Person();
singer1.setName("DAVID ");
Person singer2 = new Person();
singer2.setName("JACOB ");
music.setSingers(new Person[] { singer1, singer2 });
Human man = new Human();
Person p = new Person();
p.setName(" JACK'S RAGING BULL ");
SomeGuy m = new SomeGuy();
m.setPerson(p);
man.setMan(m);
music.setHuman(man);
return music;
}
Outcome:
#######BEFORE#######
>>[>>DAVID ---<<, >>JACOB ---<<]---[ ENGLISH , FRENCH , HINDI ]---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>METAL ---A ---B ---[SOME Y DATA , SOME OTHER DATA Y , SOME MORE DATA Y , ]---<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]---[>>---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]<<, >>{Coach =>>CARTER ---<<, Name =>>JOHN JACKSON DOE ---<<}---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>METAL ---A ---B ---[SOME Y DATA , SOME OTHER DATA Y , SOME MORE DATA Y , ]---<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]<<]---=> JACK'S RAGING BULL <=<<
Number of spaces : 644
#######AFTER#######
>>[>>DAVID---<<, >>JACOB---<<]---[ENGLISH, FRENCH, HINDI]---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>METAL---A---B---[SOME Y DATA, SOME OTHER DATA Y, SOME MORE DATA Y, ]---<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]---[>>---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]<<, >>{Name=>>JOHN JACKSON DOE---<<, Coach=>>CARTER---<<}---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>METAL---A---B---[SOME Y DATA, SOME OTHER DATA Y, SOME MORE DATA Y, ]---<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]<<]---=>JACK'S RAGING BULL<=<<
Number of spaces : 111
There is a non-zero count of the number of spaces in the above trimmed output because I didn't make an effort to override toString of any collections (List, Set) or Map. There are certain improvements to the code I want to make but for your case the solution should work just fine.
Limitations (further improvements)
Cannot handle undisciplined syntax of properties (invalid getters/setters)
Cannot handle chained Collections: for example, List<List<Person>> - because of the exclusive support to disciplined getters/setters convention
No Guava collection library support
Building off #SwissArmyKnife I converted his simple String trimming function into an interface with a default method. So any object where you would like to use object.trim(), you just have to add "implements Trimmable".
Simple String trim interface: Trimmable.class
/**
* Utility interface that trims all String fields of the implementing class.
*/
public interface Trimmable {
/**
* Trim all Strings
*/
default void trim(){
for (Field field : this.getClass().getDeclaredFields()) {
try {
field.setAccessible(true);
Object value = field.get(this);
if (value != null){
if (value instanceof String){
String trimmed = (String) value;
field.set(this, trimmed.trim());
}
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
An object that we would like to be trimmable: Person.class (implements Trimmable interface)
public class Person implements Trimmable {
private String firstName;
private String lastName;
private int age;
// getters/setters omitted
}
Now you can use person.trim()
Person person = new Person();
person.setFirstName(" John ");
person.setLastName(" Doe");
person.setAge(30);
person.trim();
I made a simple method for trimming String values with Reflection API.
public Object trimStringValues(Object model){
for(Field field : model.getClass().getDeclaredFields()){
try{
field.setAccessible(true);
Object value = field.get(model);
String fieldName = field.getName();
if(value != null){
if(value instanceof String){
String trimmed = (String) value;
field.set(model, trimmed.trim());
}
}
}catch(Exception e){
e.printStackTrace();
}
}
}
I haven't bumped in to any problems with this one yet. I know its an old thread, but it might help somone whos is looking for something simple.
I've read the other posts and the docs about how to use the "Where" clause to "create" parenthesis statements.
My requirement is simple:
... WHERE companyID=1 AND (director=true OR officer=true) ;
I'm writing a routine that takes an array of Object, which are then parsed into an Ormlite Where call. a typical call looks like this:
.., "companyID", 1, Q.AND, Q.Bracket, "director", true, Q.OR, "officer", true, Q.Bracket)
The intent is to speed up simple queries. There is no desire to replace Ormlite's querying tools. This is a simple meta-layer on top.
Everything works fine for simple queries, since the parameters are processed sequentially and the where clause is built incrementally.
For parenthesis I am postponing the processing until the bracket is closed.
This is where I am having a problem. The example from the docs I am using shows this:
-- From the OrmLite docs...
Where<Account, String> where = queryBuilder.where();
where.or(
where.and(
where.eq(Account.NAME_FIELD_NAME, "foo"),
where.eq(Account.PASSWORD_FIELD_NAME, "_secret")),
where.and(
where.eq(Account.NAME_FIELD_NAME, "bar"),
where.eq(Account.PASSWORD_FIELD_NAME, "qwerty")));
This produces the following approximate SQL:
SELECT * FROM account
WHERE ((name = 'foo' AND password = '_secret')
OR (name = 'bar' AND password = 'qwerty'))
The key thing I understand from the docs example, is that the same where instance is used in the nested and(...) call. This is precisely what I'm doing but I'm still getting a "Did you forget an AND or an OR" message.
The code implementing the "delayed" processing looks like this:
#SuppressWarnings("unchecked")
private void processWhere(Where<?, ?> where, Q q, List<QValue> list)
{
if (null == list || list.size() < 2)
{
System.err.println("Invalid where passed: " + list);
return;
}
if (q.equals(Q.AND))
where.and(getCondition(where, list.get(0)), getCondition(where, list.get(1)));
else
where.or(getCondition(where, list.get(0)), getCondition(where, list.get(1)));
}
The "QValue" item is just a "holder" for column, condition and value data.
The "getCondition" method is as follows:
#SuppressWarnings("rawtypes")
protected Where getCondition(Where<?, ?> where, QValue qv)
{
if (null != where && null != qv)
return getCondition(where, qv.getType(), qv.getColumn(), qv.getValue(), qv.getValue2());
else
return null;
}
#SuppressWarnings("rawtypes")
protected Where getCondition(Where<?, ?> where, Q cond, String key, Object val, Object val2)
{
if (null == where || null == cond || null == key || null == val)
return null;
SelectArg arg = new SelectArg();
arg.setValue(val);
try
{
switch (cond)
{
case NotNull:
where.isNotNull(key);
break;
case IsNull:
where.isNull(key);
break;
case Equals:
where.eq(key, arg);
break;
case NotEqual:
where.ne(key, arg);
break;
case GreaterThan:
where.gt(key, arg);
break;
case LessThan:
where.lt(key, arg);
break;
case Like:
arg.setValue("%" + val + "%");
where.like(key, arg);
break;
case LikeStart:
arg.setValue("" + val + "%");
where.like(key, arg);
break;
case LikeEnd:
arg.setValue("%" + val);
where.like(key, arg);
break;
case Between:
if (null != val && null != val2)
where.between(key, val, val2);
break;
default:
where.eq(key, arg);
break;
}
}
catch (SQLException e)
{
GlobalConfig.log(e, true);
return null;
}
return where;
}
As far as I can tell, I'm using the Where object correctly, but I am still getting a:
"Did you forget an AND or OR?" message.
I've tried creating "new" Where clauses with QueryBuilder:
Where w1 = qb.where() ;
//process w1 conditions...
return where.query() ;
Which also fails or generates incorrect SQL in the various combinations I've tried. Any suggestions on how to get the and(...) and or(...) methods working properly will be greatly appreciated.
BTW once the library is working properly, I'll put it up as Open Source or donate it to Gray, or both.
Thanks in advance.
Anthony
I faced the same issue and solved it like this:
where.eq("companyID", 1);
where.and(where, where.or(where.eq("director", true), where.eq("officer", true)));
or
where.and(where.eq("companyID", 1), where.or(where.eq("director", true), where.eq("officer", true)));
which in SQL gives us:
((`companyID` = 1 AND `director` = 1 ) OR (`companyID` = 1 AND `officer` = 1 ))
It's not identical to your example clause WHERE companyID=1 AND (director=true OR officer=true) but has the same meaning.
I have a field that I am trying to set the length of 25 to by using StringBuilder and then populate it with string values in specific positions within that field. However, when I get a print out of the values in that field the value looks like this:
M0
Obviously I am needing to remove the "�" values from that field. Any help/direction would be appreciated.
Here is my code:
String b44 = toRequestIsoMessage.getString(B44_ADD_RESPONSE_DATA.bitId);
if (b44 == null) {
// ***** 20130604 MS - Told Ralph since that position 1 is space filled initially in the request to the CORE so that he can modify for the AVS. *****
String avsValue = " ";
try {
StringBuilder revB44Value = new StringBuilder();
revB44Value.setLength(25);
revB44Value.insert(0, avsValue);
if (decision.cidResponse.responseCode != null) {
revB44Value.insert(1, decision.cidResponse.responseCode);
} else {
revB44Value.insert(1, " ");
}
if (decision.cvvResponse.responseCode != null) {
revB44Value.insert(13, decision.cvvResponse.responseCode);
} else {
revB44Value.insert(13, " ");
}
String revB44 = revB44Value.toString();
toRequestIsoMessage.setString(B44_ADD_RESPONSE_DATA.bitId, revB44Value.toString());
} catch (InternalISOMsgException e) {
LOGGER.info(FormatData.fullStackTrace(e));
}
}
How can I detect when a json value is null?
for example: [{"username":null},{"username":"null"}]
The first case represents an unexisting username and the second a user named "null". But if you try to retrieve them both values result in the string "null"
JSONObject json = new JSONObject("{\"hello\":null}");
json.put("bye", JSONObject.NULL);
Log.e("LOG", json.toString());
Log.e("LOG", "hello="+json.getString("hello") + " is null? "
+ (json.getString("hello") == null));
Log.e("LOG", "bye="+json.getString("bye") + " is null? "
+ (json.getString("bye") == null));
The log output is
{"hello":"null","bye":null}
hello=null is null? false
bye=null is null? false
Try with json.isNull( "field-name" ).
Reference: http://developer.android.com/reference/org/json/JSONObject.html#isNull%28java.lang.String%29
Because JSONObject#getString returns a value if the given key exists, it is not null by definition. This is the reason JSONObject.NULL exists: to represent a null JSON value.
json.getString("hello").equals(JSONObject.NULL); // should be false
json.getString("bye").equals(JSONObject.NULL); // should be true
For android it will raise an JSONException if no such mapping exists. So you can't call this method directly.
json.getString("bye")
if you data can be empty(may not exist the key), try
json.optString("bye","callback string");
or
json.optString("bye");
instead.
In your demo code, the
JSONObject json = new JSONObject("{\"hello\":null}");
json.getString("hello");
this you get is String "null" not null.
your shoud use
if(json.isNull("hello")) {
helloStr = null;
} else {
helloStr = json.getString("hello");
}
first check with isNull()....if cant work then try belows
and also you have JSONObject.NULL to check null value...
if ((resultObject.has("username")
&& null != resultObject.getString("username")
&& resultObject.getString("username").trim().length() != 0)
{
//not null
}
and in your case also check resultObject.getString("username").trim().eqauls("null")
If you must parse json first and handle object later, let try this
Parser
Object data = json.get("username");
Handler
if (data instanceof Integer || data instanceof Double || data instanceof Long) {
// handle number ;
} else if (data instanceof String) {
// hanle string;
} else if (data == JSONObject.NULL) {
// hanle null;
}
Here's a helper method I use so that I can get JSON strings with only one line of code:
public String getJsonString(JSONObject jso, String field) {
if(jso.isNull(field))
return null;
else
try {
return jso.getString(field);
}
catch(Exception ex) {
LogHelper.e("model", "Error parsing value");
return null;
}
}
and then something like this:
String mFirstName = getJsonString(jsonObject, "first_name");
would give you your string value or safely set your string variable to null. I use Gson whenever I can to avoid pitfalls like these. It handles null values much better in my opinion.