如何从一个方法，另一个类的变量数据中读取公共静态变量并获取更新的数据

Question

I need to read in the 'public static NEW_QUERY' from another class, but it has variables inside of the query that is changed when the method is called. How can I call this 'public static' and get the updated QUERY from another class.

Here is the Java Code;

package artemispm.autocalc;

import java.sql.*;
import java.util.*;
import a7.unittests.dao.UnitTestHelper;
import artemispm.serverutil.*;
import artemispm.trdo.*;
import artemispm.parser.*;

public abstract class TRBaseScoreCalculator implements ExpressionParserLookup {

/******THIS IS THE PLACE I NEED TO HAVE CORRECTED**********/
/*HOW DO I FORCE THIS TO PUSH VALUES INTO 'match' and 'useFor'*/
/**SO THAT I CAN CALL NEW_QUERY FROM ANOTHER CLASS *****/
/****IT SAYS 'match' and 'useFor' cannot be resolved****/

public static String NEW_QUERY = "select count(userfieldid) from tr_userfield where calcexpression like '%" + match + "%'and usefor like '%" + useFor +"%'";

public Connection               m_con;
protected String                m_characName        = "";

public boolean isThisCharacInUse(Connection con, String characName,String useFor) 
throws SQLException, TRException {
    boolean result;        
    String match = "[" + TRBaseSql.rewrapQuotes(characName) + "]";

    if(TRBaseSql.getDatabaseType(con) == TRBaseSql.DBTYPESQLSERVER) {
        match = "[[]" + TRBaseSql.rewrapQuotes(characName) + "]";
    }

    TRSystemSQL sql = new TRSystemSQL();
    TRSystem sys=sql.getSystem(con);
    result =    (   sys.getScoreCalculation() != null 
                &&  sys.getScoreCalculation().indexOf(match) >= 0  );
    if (result) return(result);
    else {

        int count;

        /*****THIS IS THE PLACE I NEED HELP AT  12/5/2012 ******/

        count = sql.executeGetInt(con, NEW_QUERY , null);

        if (count > 0) return true;
        count = sql.executeGetInt(con, 
                "select count(characid) from tr_charac where calcexpression like '%" + match + "%'and usefor like '%" + useFor +"%'" , null);
        return (count > 0);
        }
}
}

In addition to this, which I have not attempted here, but I am supposed to as it is in the specs:

• Locate all embedded sql statements and implement constants for embedded sql which does not already use constants.
• Replace any string concatenation within Sql statement creation with String.format().

• For any String.format commands you must escape out any existing % symbols. These symbols are often used in LIKE operations.

  What I am doing is Unit Testing each Query, from another file, to make sure they are correct for data migration from a MSSQL Server 2005 to MYSQL

IS THE BELOW THE BEST SOLUTION GIVEN THE STRING.FORMAT SPEC. IS THIS CORRECT. THE TEST DOES PASS, BUT I THOUGHT I WAS SUPPOSED TO CHANGE AS LITTLE OF THE ORIGINAL CODE AS POSSIBLE

package artemispm.autocalc;

import java.sql.*;
import java.util.*;
import a7.unittests.dao.UnitTestHelper;
import artemispm.serverutil.*;
import artemispm.trdo.*;
import artemispm.parser.*;

public abstract class TRBaseScoreCalculator implements ExpressionParserLookup {

/******THIS IS THE PLACE I NEED TO HAVE CORRECTED**********/
/*HOW DO I FORCE THIS TO PUSH VALUES INTO 'match' and 'useFor'*/
/**SO THAT I CAN CALL NEW_QUERY FROM ANOTHER CLASS *****/
/****IT SAYS 'match' and 'useFor' cannot be resolved****/

public static String NEW_QUERY = String.format( "select count(userfieldid) from tr_userfield where calcexpression like %s and usefor like %s", "?", "?");

public Connection               m_con;
protected String                m_characName        = "";

public boolean isThisCharacInUse(Connection con, String characName,String useFor) 
throws SQLException, TRException {
    boolean result;        
    String match = "[" + TRBaseSql.rewrapQuotes(characName) + "]";

    if(TRBaseSql.getDatabaseType(con) == TRBaseSql.DBTYPESQLSERVER) {
        match = "[[]" + TRBaseSql.rewrapQuotes(characName) + "]";
    }

    TRSystemSQL sql = new TRSystemSQL();
    TRSystem sys=sql.getSystem(con);
    result =    (   sys.getScoreCalculation() != null 
                &&  sys.getScoreCalculation().indexOf(match) >= 0  );
    if (result) return(result);
    else {

        int count;

        /*****THIS IS THE PLACE I NEED HELP AT  12/5/2012 ******/

        PreparedStatement stmt = con.prepareStatement(TRBaseScoreCalculator.NEW_QUERY);
        stmt.setString(1, "%"+match+"%");
        stmt.setString(2, "%"+useFor+"%");

        count = sql.executeGetInt(con, stmt.toString() , null);

        if (count > 0) return true;
        count = sql.executeGetInt(con, 
                "select count(characid) from tr_charac where calcexpression like '%" + match + "%'and usefor like '%" + useFor +"%'" , null);
        return (count > 0);
        }
}
}

Answer 1

Static variables/methods are associated with lass definition and hence you can't use any non-static variable/method in them.

if your match and useFor are not static(that is the case) then you can't have a static qquery like this:

public static String NEW_QUERY = "select count(userfieldid) from tr_userfield where calcexpression like '%" + match + "%'and usefor like '%" + useFor +"%'";

Better to use a place holders in the query as:

 public static String NEW_QUERY = 
           "select count(userfieldid) from tr_userfield "+
            " where calcexpression like ? and usefor like ?";

and the place of use, pass the value using query Parameter set methods:

   PreparedStatement stmt= con.prepareStatement(TRBaseScoreCalculator.NEW_QUERY);
   stmt.setString(1,"%"+match+"%");
   stmt.setString(1,"%"+useFor+"%");

EDIT : If you want to use String.format then try below:

 public static String NEW_QUERY =  "select count(userfieldid) from tr_userfield "+
                           "  where calcexpression like '%s' and usefor like '%s'";

and down the line where you are using the query string, do:

 String updatedQuery = String.format(TRBaseScoreCalculator.NEW_QUERY, 
                                      "%"+match+"%", "%"+useFor+"%");
 count = sql.executeGetInt(con, updatedQuery, null);

But Still I prefer the PraparedStatement route and in that case you don't need to unnecessary String.format .

Answer 2

如果您使用PreparedStatement ，则不仅会避免从静态上下文引用非静态内容的问题，而且，您的应用程序不会轻易受到损害 。