ResultAssembler.java

package com.github.walker.easydb.dao;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;

import com.github.walker.easydb.assistant.LogFactory;
import com.github.walker.easydb.assistant.MappingUtil;
import com.github.walker.easydb.exception.FileAccessException;
import org.apache.log4j.Logger;

import com.github.walker.easydb.assistant.EasyConfig;
import com.github.walker.easydb.exception.DataAccessException;
import com.github.walker.easydb.exception.IllegalEntityException;

/**
 * This class builds the BaseEntity object. It transforms query result into
 * BaseEntity object, and put the BaseEntity instance into PageList object.
 *
 * @author HuQingmiao
 */
public abstract class ResultAssembler {

    protected Logger log = LogFactory.getLogger(this.getClass());

    // 当读取大字段列时, 需要设置的存放EBinFile或ETxtFile的目录
    protected static String BASE_FILE_DIRC = EasyConfig.getProperty("baseFileDirc");

    // the constructor of BaseEntity
    @SuppressWarnings("rawtypes")
    protected Constructor cons;

    // the map(index, SettingMethodExp)
    protected HashMap<Integer, SettingMethodExp> indexMethodExpMap;

    protected int colCount;// the column count

    // the Class object of the BaseEntity
    protected Class<?> entityClass;

    // query result
    protected ResultSet rs;

    protected ArrayList<BaseEntity> rsList;

    /**
     * 获取数据库类型
     *
     * @return 数据库类型, 如'mysql', 'oracle'
     */
    public abstract String getDBType();

    /**
     * Constructor of ResultAssembler
     *
     * @param rs          ResultSet object.
     * @param entityClass The Class object of BaseEntity which used to load the query
     *                    result.
     * @throws IllegalEntityException
     * @throws DataAccessException
     */
    public ResultAssembler(ResultSet rs, Class<?> entityClass) {
        this.rs = rs;
        this.entityClass = entityClass;
    }

    /**
     * Analyzes the query result and put it into PageList.
     *
     * @throws IllegalEntityException
     * @throws DataAccessException
     */
    public void buildEntityList() throws IllegalEntityException, DataAccessException, FileAccessException {

        this.analyzeRs();

        this.buildList();

    }

    /**
     * Load data to the specified entity
     */
    protected boolean loadEntity(BaseEntity entity) throws IllegalEntityException, DataAccessException,
            FileAccessException {

        this.analyzeRs();

        return this.loadData(entity);
    }

    /**
     * Analyzes the structure of Entity Class which instance used to loading
     * query result.
     *
     * @throws IllegalEntityException
     * @throws DataAccessException
     */
    protected void analyzeRs() throws IllegalEntityException, DataAccessException {
        this.indexMethodExpMap = new HashMap<Integer, SettingMethodExp>();

        try {
            // Get the constructor that without any parameter
            Class<?>[] types = new Class[]{};
            this.cons = entityClass.getConstructor(types);

            // Get the entity instance by the constructor and empty parameter
            Object[] args = new Object[]{};
            Object entity = cons.newInstance(args);

            Field[] fields = entity.getClass().getDeclaredFields();

            // 将fields缓存到map(fieldName,field)
            HashMap<String, Field> fieldMap = new HashMap<String, Field>();
            for (int i = 0; i < fields.length; i++) {
                fieldMap.put(fields[i].getName(), fields[i]);
            }

            ResultSetMetaData rsmd = rs.getMetaData();
            this.colCount = rsmd.getColumnCount();

            /**
             * 列_PAGER_ROW 是分页查询的行号. 若给定的SQL需要查询所有列(如" SELECT * FROM ... "),
             * 则经过分页构造后的SQL必定有行号（ROWNUM _PAGER_ROW）这一列, 而实体类中没有声明对应属性, 因此必须忽略此列。
             */
            // 判断最后一列是否是分页查询的行号, 如果是则滤掉
            String colName = rsmd.getColumnName(colCount);
            if (colName.equals("PAGER_ROW")) {
                this.colCount--;
            }

            // the method name of class BaseEntity
            StringBuffer methodName = new StringBuffer();
            Method method = null;

            for (int col = 1; col <= colCount; col++) {
                colName = rsmd.getColumnName(col);

                String fieldName = MappingUtil.getFieldName(colName);

                Field field = (Field) fieldMap.get(fieldName);

                // no field matching the column name
                if (field == null) {
                    // throw new IllegalEntityException(
                    // IllegalEntityException.ILLEGAL_ENTITY, entityClass
                    // .getName()
                    // + "#" + fieldName);
                    continue;
                }
                String fieldType = field.getType().getName();

                // builds the method name, such as: "setXX"
                String firstChar = fieldName.substring(0, 1).toUpperCase();
                if (fieldName.length() > 1 && Character.isUpperCase(fieldName.charAt(1))) {
                    firstChar = firstChar.toLowerCase();
                }
                methodName.append("set").append(firstChar).append(fieldName.substring(1));
                method = entity.getClass().getMethod(methodName.toString(), new Class[]{Class.forName(fieldType)});
                methodName.delete(0, methodName.length());

                // put the method object into MethodExp vector
                indexMethodExpMap.put(new Integer(col), new SettingMethodExp(fieldType, method));

            }

            fieldMap.clear();

        } catch (NoSuchMethodException e) {
            log.error("", e);
            throw new IllegalEntityException(e.getMessage());
        } catch (InstantiationException e) {
            log.error("", e);
            throw new IllegalEntityException(e.getMessage());
        } catch (IllegalAccessException e) {
            log.error("", e);
            throw new IllegalEntityException(e.getMessage());
        } catch (InvocationTargetException e) {
            log.error("", e);
            throw new IllegalEntityException(e.getMessage());
        } catch (SQLException e) {
            log.error("", e);
            throw new DataAccessException(e.getMessage());
        } catch (ClassNotFoundException e) {
            log.error("", e);
            throw new IllegalEntityException(e.getMessage());
        } catch (Exception e) {
            log.error("", e);
        }
    }

    /**
     * Builds PageList object with query result.
     *
     * @return
     * @throws IllegalEntityException
     * @throws DataAccessException
     */
    protected abstract void buildList() throws IllegalEntityException, DataAccessException, FileAccessException;

    protected abstract boolean loadData(BaseEntity entity) throws IllegalEntityException, DataAccessException,
            FileAccessException;

    /**
     * @return the ArrayList object that have already assembled.
     */
    public abstract ArrayList<BaseEntity> getRsList();
}