query Parser

package com.innovaatio.query.parser;

import java.util.ArrayList;
import java.util.List;

import com.innovation.model.Criteria;
import com.innovation.model.Field;
import com.innovation.model.Query;

public class QueryParser {

Query query = new Query();
public Query Parse(String strQuery){
final int selectIndex = (strQuery.indexOf("SELECT") != -1) ? strQuery.indexOf("SELECT") : strQuery.indexOf("select");
        final int fromIndex = (strQuery.indexOf("FROM") != -1) ? strQuery.indexOf("FROM") : strQuery.indexOf("from");;
        final int whereIndex = (strQuery.indexOf("WHERE") != -1) ? strQuery.indexOf("WHERE") : strQuery.indexOf("where");
        final int orderByIndex = (strQuery.indexOf("ORDERBY") != -1) ? strQuery.indexOf("ORDERBY") : strQuery.indexOf("orderby");
        if (selectIndex == -1){
        query.setSelect(false);
        return query;
        }
       
        if (fromIndex == -1){
        query.setParseMessage("Invalid SQL, missing the from clause");
        return query;
        }
        String tableName = strQuery.substring(fromIndex, whereIndex).trim().substring(4);
        query.setTableName(tableName);
        String criteriaStr = null;
        if(orderByIndex != -1){
        String orderByField =  strQuery.substring(orderByIndex).trim().substring(7).trim();
        criteriaStr = strQuery.substring(whereIndex, orderByIndex).trim().substring(5);
        query.setSortByFieldName(orderByField);
        }else{
        criteriaStr = strQuery.substring(whereIndex).trim();
        }
        query.setCriteriaList(parseCriteriaList(criteriaStr));
        return query;
}

private String getOperator(String condition){
if(condition.contains("=")){
return "=";
}else if(condition.contains("<")){
return "<";
}else if(condition.contains(">")){
return ">";
}else if(condition.contains("<>")){
return "<>";
}
return "";
}

private Criteria getCriteria(String criteria){
Criteria criteriaObj = null;
if(criteria.contains("=") || criteria.contains("<") || criteria.contains(">") || criteria.contains("<>")){
String[] fields = criteria.split(getOperator(criteria));
if(fields.length == 2){
criteriaObj = new Criteria(getOperator(criteria), new Field(fields[0],fields[1]));
}
}

return criteriaObj;
}

public List<Criteria> parseCriteriaList(String criteriaStr){
List<Criteria> criteriaList = new ArrayList<Criteria>();
if(criteriaStr.indexOf("AND") != -1 || criteriaStr.indexOf("and") != -1){
int andIndex = (criteriaStr.indexOf("AND") != -1) ? criteriaStr.indexOf("AND") : criteriaStr.indexOf("and");
if(andIndex != -1){
query.setLogicalOperator("AND");
String[] criteriaArr = (criteriaStr.split("AND").length == 2)?criteriaStr.split("AND"):criteriaStr.split("and");
for(String criteria: criteriaArr){
criteriaList.add(getCriteria(criteria));
}
}
}else if(criteriaStr.indexOf("OR") != -1 || criteriaStr.indexOf("or") != -1){
int orIndex = (criteriaStr.indexOf("OR") != -1) ? criteriaStr.indexOf("OR") : criteriaStr.indexOf("or");
if(orIndex != -1){
query.setLogicalOperator("OR");
String[] criteriaArr = (criteriaStr.split("OR").length == 2)?criteriaStr.split("OR"):criteriaStr.split("or");
for(String criteria: criteriaArr){
criteriaList.add(getCriteria(criteria));
}
}
}
return criteriaList;
}
}

package com.innovation.service;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import com.innovation.model.Employee;

public class MappingService {

public static void main(String[] args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException, SecurityException, InstantiationException {

Employee emp = Employee.class.newInstance();

Class  aClass = Employee.class;

List<String> fieldList = Arrays.asList("firstName","lastName","empId","designation");

Map<String, Object> queryResult = new HashMap<String, Object>();

queryResult.put("firstName", "Amit");

queryResult.put("lastName", "Sharma");

queryResult.put("empId", 11380);

queryResult.put("designation", "Development Engineer");

for(String field:fieldList){

Field pvtField = aClass.getDeclaredField(field);

pvtField.setAccessible(true);

pvtField.set(emp,queryResult.get(field));

}

System.out.println("Employee::"+emp.toString());

}

}

package com.innovation.model;

import java.util.List;

public class Query {

private boolean isSelect;

private List<String> columns;

private String tableName;

private String sortByFieldName;

private String logicalOperator;

private List<Criteria> criteriaList;

private String parseMessage;

public List<Criteria> getCriteriaList() {

return criteriaList;

}

public void setCriteriaList(List<Criteria> criteriaList) {

this.criteriaList = criteriaList;

}

public boolean isSelect() {

return isSelect;

}

public void setSelect(boolean isSelect) {

this.isSelect = isSelect;

}

public List<String> getColumns() {

return columns;

}

public void setColumns(List<String> columns) {

this.columns = columns;

}

public String getTableName() {

return tableName;

}

public void setTableName(String tableName) {

this.tableName = tableName;

}

public String getSortByFieldName() {

return sortByFieldName;

}

public void setSortByFieldName(String sortByFieldName) {

this.sortByFieldName = sortByFieldName;

}

public String getParseMessage() {

return parseMessage;

}

public void setParseMessage(String parseMessage) {

this.parseMessage = parseMessage;

}

public String getLogicalOperator() {

return logicalOperator;

}

public void setLogicalOperator(String logicalOperator) {

this.logicalOperator = logicalOperator;

}

}

package com.innovation.model;

public class Employee {

private String firstName;

private String lastName;

private int empId;

private String designation;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public int getEmpId() {

return empId;

}

public void setEmpId(int empId) {

this.empId = empId;

}

public String getDesignation() {

return designation;

}

public void setDesignation(String designation) {

this.designation = designation;

}

@Override

public String toString() {

return "FirstName:" + firstName + "\nLastName:" + lastName + "\nEmpId:"

+ empId + "\nDesignation:" + designation;

}

}

package com.innovation.model;

public class Field {

private String name;

private String value;

public Field(){}

public Field(String name, String value){

this.name = name;

this.value = value;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getValue() {

return value;

}

public void setValue(String value) {

this.value = value;

}

}

package com.innovation.model;

public class Criteria {

private String operator;

private Field field;

public Criteria(){}

public Criteria(String operator, Field field){

this.operator = operator;

this.field = field;

}

public Field getField() {

return field;

}

public void setField(Field field) {

this.field = field;

}

public String getOperator() {

return operator;

}

public void setOperator(String operator) {

this.operator = operator;

}

}