Alejandro Barrero

My problem is with code that was working before:
public CachedRowSetImpl getObjectsRowSet(String selectStatement) { selectStatement = selectStatement.replace("false", "0"); selectStatement = selectStatement.replace("true", "-1"); selectStatement = selectStatement.replace("FALSE", "0"); selectStatement = selectStatement.replace("TRUE", "-1"); CachedRowSetImpl rowSet = null; Connection conn = null; try { conn = this.dataSource.getConnection(); Statement statement = conn.createStatement(); ResultSet result = statement.executeQuery(selectStatement); rowSet = new CachedRowSetImpl(); rowSet.populate(result); } catch (SQLException e) { MainFrame.displayExitErrorMessage(e); } finally { try { if (conn != null) conn.close(); } catch (SQLException e) { MainFrame.displayExitErrorMessage(e); } } return rowSet; }

I am geting the message: "CachedRowSetImpl cannot be resolved to a type". I dont know why I lost the jar file, but I was able to down load com.sun.rowset with CachedRowSetImpl.class. I was able to set the jar file at libraries at "Java Build Pat" and everything shows in Package Explorer at Referenced Libraries. I cannot understand what is going wrong?

No I can see the source code. What I cannot see is the tab that shows graphically the class presentation.

I canot longer open a Java class file with the option to see the page with two tabs at the bottom one for the code and the other to view the structure.

My apologies, I was looking at the wrong database.

I have the following class:
public class SQLiteJdbc { /** * @param args */ public static void main(String[] args) { Connection conn = connect(); try { Statement stmt = conn.createStatement(); String sql = "INSERT INTO document (date_created,assigned_to_processor,cancelled,complete,reviewed,reason_for_return,next_event,assigned,name,primary_key) VALUES ('2021-01-23',1,0,0,0,NULL,1,1,'xxxx',0)"; stmt.executeUpdate(sql); } catch (Exception e) { e.printStackTrace(); } } /** * @return */ public static Connection connect() { Connection conn = null; try { MainFrame.DATABASE_DIRECTORY = "C:\\SAV\\Database"; String databaseFilepath = MainFrame.DATABASE_DIRECTORY + File.separator + MainFrame.PAPERLESS_DATABASE; String url = "jdbc:sqlite:" + databaseFilepath; // create a connection to the database Class.forName("org.sqlite.JDBC"); conn = DriverManager.getConnection(url); conn.setAutoCommit(true); } catch (SQLException | ClassNotFoundException e) { System.out.println(e.getMessage()); } return conn; } }
The code runs correctly executing may SQL statements.
The problem is that executing "stmt.executeUpdate(sql);" in method main I get the error "java.sql.SQLException: PRIMARY KEY must be unique". However table "document" has no rows. I just can't understand.

Thank you very much; however, this code  has been working for years and it was working las week. Well, it looks bad and I will eliminate it any way.

I have the following test Class:
package com.test; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class SQLiteJdbc { public static void main(String[] args) { Connection conn = connect(); try { Statement stmt = conn.createStatement(); String sql = "SELECT * FROM user";      ResultSet rs = stmt.executeQuery(sql);      while(rs.next()){       String name = rs.getString("first_name");   System.out.println("Name is " + name);      } } catch (SQLException e) { e.printStackTrace(); } } public static Connection connect() { Connection conn = null; try { // db parameters String url = "jdbc:sqlite:C:\\SAV\\Database\\PaperlessOffice.db"; // create a connection to the database Class.forName("org.sqlite.JDBC"); conn = DriverManager.getConnection(url); } catch (SQLException | ClassNotFoundException e) { System.out.println(e.getMessage()); } finally { try { if (conn != null) { conn.close(); } } catch (SQLException ex) { System.out.println(ex.getMessage()); } } return conn; } }
My problem is that the code was working a week ago, but now i am getting java.lang.NullPointerException in  Class Stmt in package org.sqlite at lin6 of method main  and line 121 in executeQuery. Method connect appears to work correctly and I still have the database in the same path.
I don't remember changing anything.

I started creating an application from a book; it started running fine after I created the application with ng new; however after I changed app.component.ts and app.component.html I keep getting the same result in the browser no matter how many times I run   ng serve.

Unfortunately I cannot display images, so I have to type the structure of the application
Paperless Office
   src
       com.help.utils
       com.orm
       ....
       com.resources
           action_add.gif
           ...
           arrow_top.gif
           ...
   bin
       com
           help
           ....
           resources
               action_add.gif
               ...
               arrow_top.gif
               ...

I have been using this code for years
this.jScrollUpMessages.setIcon( new javax.swing.ImageIcon(getClass().getResource("/com/resources/arrow_top.gif")));
But suddenly getClass().getResource("/com/resources/arrow_top.gif") is giving me a null value. I have no idea what I have done wrong with the application. If worse comes to worse, I can rewrite the codes in several ways, but there are hundreds of lines; I wish I could find a solution.

My apologies for taking your time. I don't have to convert the JSON  string; the following client code works fine
public static ArrayList<User> getResultSet(String selectStatement) { RestTemplate restTemplate = new RestTemplate(); ResponseEntity<User[]> response = restTemplate.getForEntity("http://localhost:8080/resultSet/{selectStatement}", User[].class, selectStatement); User[] arrayOfObjects = response.getBody(); ArrayList<User> listOfObjects = new ArrayList<>(); for(User nextUser : arrayOfObjects) { listOfObjects.add(nextUser); } return listOfObjects; }

Thanks for the replies. I was trying plain JSON at the beginning but had difficulties. GSON constructs the string i want to return correctly; the problem is that I cannot construct the Java ArrayList or array, please tell me how to do it.

I have the following REST controller
@RestController public class PaperlessController { @ResponseBody @RequestMapping(path = "/resultSet/{selectStatement}", produces = MediaType.APPLICATION_JSON_VALUE) @GetMapping() public String objects(@PathVariable String selectStatement) { ArrayList<PersistentObject> listOfObjects = new ArrayList<>(); String[] words = selectStatement.split(" "); // The name of the table in SQL statement "Select * From table ...". String table = words[3]; Connection conn = null; try { conn = getConnection(); Statement statement = conn.createStatement(); ResultSet resultSet = statement.executeQuery(selectStatement); while (resultSet.next()) { PersistentObject nextObject = persistentObject(table); nextObject.copyProperties(resultSet); listOfObjects.add(nextObject); } ObjectsWrapper objects = new ObjectsWrapper(listOfObjects); Gson gson = new Gson(); String jsonString = null; jsonString = gson.toJson(objects); // Try to construct the list of User fro JSON string. ArrayList<User> users = gson.fromJson(jsonString, new TypeToken<ArrayList<User>>() {}.getType()); return jsonString; } catch (SQLException e) { return null; } finally { try { if (conn != null) conn.close(); } catch (SQLException e) { return null; } } }
Without
// Try to construct the list of User fro JSON string. ArrayList<User> users = gson.fromJson(jsonString, new TypeToken<ArrayList<User>>() {}.getType());
The code runs fine in the debugger and executes fine with Posman. However, with this addition I am getting the error
java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $
at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:351) ~[gson-2.8.6.jar:na]
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:80) ~[gson-2.8.6.jar:na]
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61) ~[gson-2.8.6.jar:na]
at com.google.gson.Gson.fromJson(Gson.java:932) ~[gson-2.8.6.jar:na]
at com.google.gson.Gson.fromJson(Gson.java:897) ~[gson-2.8.6.jar:na]
at com.google.gson.Gson.fromJson(Gson.java:846) ~[gson-2.8.6.jar:na]
at com.paperless.controler.PaperlessController.objects(PaperlessController.java:67) ~[classes/:na]
What I am trying to do is create the code for the client, but I am getting this error.

Using @RestController didn't make any difference.

I am getting the following exception
08:50:04.362 [main] DEBUG org.springframework.web.client.RestTemplate - HTTP GET http://localhost:8080/resultSet/select%20*%20from%20user 08:50:04.420 [main] DEBUG org.springframework.web.client.RestTemplate - Accept=[application/json, application/*+json] 08:50:37.465 [main] DEBUG org.springframework.web.client.RestTemplate - Response 500 INTERNAL_SERVER_ERROR Exception in thread "main" org.springframework.web.client.HttpServerErrorException$InternalServerError: 500 : [{"timestamp":"2020-08-28T12:50:37.427+0000","status":500,"error":"Internal Server Error","message":"","path":"/resultSet/select%20*%20from%20user"}] at org.springframework.web.client.HttpServerErrorException.create(HttpServerErrorException.java:100) at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:186) at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:125) at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63) at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:782) at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:740) at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:674) at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:315) at com.paperless.client.SelectClient.getResultSet(SelectClient.java:25) at com.paperless.client.SelectClient.main(SelectClient.java:19)
The client code is
package com.paperless.client; import java.net.URL; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import org.springframework.web.client.RestTemplate; import com.orm.PersistentObject; import com.paperless.Select_Conn; public class SelectClient { public static void main(String[] args) { String selectStatement = "select * from user"; ArrayList<PersistentObject> resultSet = getResultSet(selectStatement); } public static ArrayList<PersistentObject> getResultSet(String selectStatement) { ArrayList<PersistentObject> listOfObjects = new ArrayList<>(); RestTemplate restTemplate = new RestTemplate(); PersistentObject[] arrayOfObjects = restTemplate.getForObject("http://localhost:8080/resultSet/{selectStatement}", PersistentObject[].class, selectStatement); for (int i = 0; i < arrayOfObjects.length; i++) { ; listOfObjects.add(arrayOfObjects[i]); } return listOfObjects; } }
The controller is
package com.paperless.controler; import java.io.InputStream; import java.net.URL; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import com.orm.PersistentObject; import com.paperless.business.DocumentEvent; import com.paperless.business.DocumentType; import com.paperless.business.EnteredString; import com.paperless.business.Licenses; import com.paperless.business.Signature; import com.paperless.persistent.Attachment; import com.paperless.persistent.Control; import com.paperless.persistent.Document; import com.paperless.persistent.ProcessingStep; import com.paperless.persistent.User; @Controller public class PaperlessController { @ResponseBody @RequestMapping(path="/resultSet/{selectStatement}")  @GetMapping() public PersistentObject[] arrayOfObjects(@PathVariable String selectStatement) { ArrayList<PersistentObject> listOfObjects = new ArrayList<>(); String[] words = selectStatement.split(" "); // The name of the table in SQL statement "Select * From table ...". String table = words[3]; Connection conn = null; try { conn = getConnection(); Statement statement = conn.createStatement(); ResultSet resultSet = statement.executeQuery(selectStatement);    while(resultSet.next()) {     // For each row construct a String with column name, column type and column value.     StringBuilder nextRow = new StringBuilder(); PersistentObject nextObject = persistentObject(table); nextObject.copyProperties(resultSet); listOfObjects.add(nextObject); } int numberOfObjects = listOfObjects.size(); PersistentObject[] arrayOfObjects = new PersistentObject[numberOfObjects]; for(int i=0; i<numberOfObjects;i++) { > arrayOfObjects[i] = listOfObjects.get(i); } return arrayOfObjects; } catch (SQLException e) { return null; } finally { try { if (conn != null) conn.close(); } catch (SQLException e) { return null; } } } private PersistentObject persistentObject(String table) { PersistentObject persistentObject = null; switch (table) { case "attachment" : persistentObject = new Attachment(); break; case "control" : persistentObject = new Control(); break; case "document" : persistentObject = new Document(); break; case "document_event" : persistentObject = new DocumentEvent(); break; case "document_type" : persistentObject = new DocumentType(); break; case "entered_string" : persistentObject = new EnteredString(); break; case "licenses" : persistentObject = new Licenses(); break; case "processing_step" : persistentObject = new ProcessingStep(); break; case "signatures" : persistentObject = new Signature(); break; case "user" : persistentObject = new User(); } return persistentObject; }  private Connection getConnection() throws SQLException {    URL url = getClass().getResource("PaperlessOffice.db");    String filePath = url.getFile();    String fullConnectionString = "jdbc:sqlite:" + filePath;    Connection conn = DriverManager.getConnection(fullConnectionString);    return conn; } }
In the debugger the controller is working fine.
Initially I had the same problem returning an ArrayList, so I changed the code to return an array. Currently I want to return a String; I will represent every object by a JSON string and I will write the JSON strings in the return String separated by new lines '\n'.  I still don't see a way to convert Java objects to JSON strings and how to construct Java objects from JSON Strings.