MappingUtil.java

package com.github.walker.easydb.assistant;

import com.github.walker.easydb.dao.BaseEntity;
import com.github.walker.easydb.exception.IllegalEntityException;

/**
 * mapping util class.
 *
 * @author HuQingmiao
 */
public class MappingUtil {

    /**
     * Translates table name into the class name of relative entity.
     * <p/>
     * For example: Input the parameter 'COMPANY_NAME', this method will return
     * the result 'companyName'.
     *
     * @param tableName the table name in database
     * @return the class name of BaseEntity
     */
    public static String getEntityName(String tableName) {

        StringBuffer buff = new StringBuffer(tableName.toLowerCase());

        // the first character of class name is upper case
        buff.replace(0, 1, String.valueOf(Character.toUpperCase(tableName.charAt(0))));

        // delete character '_', and convert the next character to uppercase
        for (int i = 1, length = buff.length(); i < length; ) {

            char lastCh = buff.charAt(i - 1);// the last character
            char ch = buff.charAt(i); // the current character

            // if this character is a letter, and the last character is '_'
            if (Character.isLetter(ch) && lastCh == '_') {
                buff.replace(i - 1, i, String.valueOf(Character.toUpperCase(ch)));

                buff.deleteCharAt(i);
                length--;
            } else {
                i++;
            }
        }

        return buff.toString();
    }

    /**
     * Translates column name into the field name in relative entity class.
     * <p/>
     * For example: Input the parameter 'COMPANY_NAME', this method will return
     * the result 'companyName'.
     *
     * @param columnName the column name in database
     * @return the field name of BaseEntity Class
     */
    public static String getFieldName(String columnName) {

        StringBuffer buff = new StringBuffer(columnName.toLowerCase());

        // delete character '_', and convert the next character to uppercase
        for (int i = 1, length = buff.length(); i < length; ) {

            char lastCh = buff.charAt(i - 1);// the last character
            char ch = buff.charAt(i); // the current character

            // if this character is a letter, and the last character is '_'
            if (Character.isLetter(ch) && lastCh == '_') {
                buff.replace(i - 1, i, String.valueOf(Character.toUpperCase(ch)));

                buff.deleteCharAt(i);
                length--;
            } else {
                i++;
            }
        }

        return buff.toString();
    }

    /**
     * Parses text from the given string to produce a table name that dababase
     * understands.
     * <p/>
     * <p/>
     * For example: Input the parameter 'com.walker.entity.CompanyInfo', this
     * method will return the result 'COMPANY_INFO'.
     *
     * @param entityClassName the String object, the name of Entity Class
     * @return the relative table name in dababase.
     * @throws IllegalEntityException
     */
    public static String getTableName(String entityClassName) {

        int index = entityClassName.lastIndexOf('.');
        if (index >= 0) {
            entityClassName = entityClassName.substring(index + 1);
        }

        StringBuffer buff = new StringBuffer(entityClassName);

        for (int i = 1, length = buff.length(); i < length; i++) {
            // insert character '_' before uppercase
            if (Character.isUpperCase(buff.charAt(i))) {
                buff.insert(i++, '_');
                length++;
            }
        }

        return buff.toString().toUpperCase();
    }

    /**
     * Gets the relative table name by parsing the entity object.
     *
     * @param entity BaseEntity
     * @return the relative table name in dababase.
     * @throws IllegalEntityException
     */
    public static String getTableName(BaseEntity entity) {
        String className = entity.getClass().getName();
        return getTableName(className);
    }

    /**
     * Parses text from the given string to produce a column name that dababase
     * understands.
     * <p/>
     * For example: Input the parameter 'companyName', this method will return
     * the result 'COMPANY_NAME'.
     *
     * @param fieldName the String object, the field name in entity class.
     * @return the column name that the dababase understands.
     */
    public static String getColumnName(String fieldName) {

        StringBuffer buff = new StringBuffer(fieldName);

        for (int i = 1, length = buff.length(); i < length; i++) {
            // insert character '_' before uppercase or digit
            if (Character.isUpperCase(buff.charAt(i))) {
                buff.insert(i++, '_');
                length++;
            }
        }

        return buff.toString().toUpperCase();
    }
}