jfinal數據庫方言之H2Database

不一樣的數據庫，其sql語句也有不一樣的差別，Jfinal中，數據庫方言是根據不一樣的數據庫類型，生成對應數據庫的sql語句，全部的方言類都必需要繼承自抽象類com.jfinal.plugin.activerecord.dialect.Dialect，而且重寫抽象方法，

如下爲H2Database 數據庫方言類

package com.cpy.jfinal.plugin.activerecord.dialect;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import com.jfinal.plugin.activerecord.Record;
import com.jfinal.plugin.activerecord.Table;
import com.jfinal.plugin.activerecord.dialect.Dialect;

/**
 * H2Dialect.
 */
public class H2Dialect extends Dialect {

	
	public String forTableBuilderDoBuild(String tableName) {
		return "select * from " + tableName + " where rownum < 1";
	}

	
	public String forPaginate(int pageNumber, int pageSize, String select, String sqlExceptSelect) {
		int start = (pageNumber - 1) * pageSize;
		int end = pageNumber * pageSize;
		StringBuilder ret = new StringBuilder();
		ret.append("select * from ( select row_.*, rownum rownum_ from (  ");
		ret.append(select).append(" ").append(sqlExceptSelect);
		ret.append(" ) row_ where rownum <= ").append(end).append(") table_alias");
		ret.append(" where table_alias.rownum_ > ").append(start);
		return ret.toString();
	}

	
	public String forModelFindById(Table table, String columns) {
		StringBuilder sql = new StringBuilder("select ").append(columns).append(" from ");
		sql.append(table.getName());
		sql.append(" where ");
		String[] pKeys = table.getPrimaryKey();
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
		}
		return sql.toString();
	}

	
	public String forModelDeleteById(Table table) {
		String[] pKeys = table.getPrimaryKey();
		StringBuilder sql = new StringBuilder(45);
		sql.append("delete from ");
		sql.append(table.getName());
		sql.append(" where ");
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
		}
		return sql.toString();
	}

	// insert into table (id,name) values(seq.nextval, name)
	public void forModelSave(Table table, Map<String, Object> attrs, StringBuilder sql, List<Object> paras) {
		
		sql.append("insert into ").append(table.getName()).append("(");
		StringBuilder temp = new StringBuilder(") values(");
		String[] pKeys = table.getPrimaryKey();
		int count = 0;
		for (Entry<String, Object> e: attrs.entrySet()) {
			String colName = e.getKey();
			if (table.hasColumnLabel(colName)) {
				if (count++ > 0) {
					sql.append(", ");
					temp.append(", ");
				}
				sql.append(colName);
				Object value = e.getValue();
				if (value instanceof String && isPrimaryKey(colName, pKeys) && ((String)value).endsWith(".nextval")) {
				    temp.append(value);
				} else {
				    temp.append("?");
				    paras.add(value);
				}
			}
		}
		sql.append(temp.toString()).append(")");
	}

	
	public void forModelUpdate(Table table, Map<String, Object> attrs, Set<String> modifyFlag, StringBuilder sql,
			List<Object> paras) {
		
		sql.append("update ").append(table.getName()).append(" set ");
		String[] pKeys = table.getPrimaryKey();
		for (Entry<String, Object> e : attrs.entrySet()) {
			String colName = e.getKey();
			if (modifyFlag.contains(colName) && !isPrimaryKey(colName, pKeys) && table.hasColumnLabel(colName)) {
				if (paras.size() > 0) {
					sql.append(", ");
				}
				sql.append(colName).append(" = ? ");
				paras.add(e.getValue());
			}
		}
		sql.append(" where ");
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
			paras.add(attrs.get(pKeys[i]));
		}
	}

	
	public String forDbFindById(String tableName, String[] pKeys) {
		tableName = tableName.trim();
		trimPrimaryKeys(pKeys);
		
		StringBuilder sql = new StringBuilder("select * from ").append(tableName).append(" where ");
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
		}
		return sql.toString();
	}

	
	public String forDbDeleteById(String tableName, String[] pKeys) {
		tableName = tableName.trim();
		trimPrimaryKeys(pKeys);
		
		StringBuilder sql = new StringBuilder("delete from ").append(tableName).append(" where ");
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
		}
		return sql.toString();
	}

	
	public void forDbSave(String tableName, String[] pKeys, Record record, StringBuilder sql, List<Object> paras) {
		tableName = tableName.trim();
		trimPrimaryKeys(pKeys);
		
		sql.append("insert into ");
		sql.append(tableName).append("(");
		StringBuilder temp = new StringBuilder();
		temp.append(") values(");
		
		int count = 0;
		for (Entry<String, Object> e: record.getColumns().entrySet()) {
			String colName = e.getKey();
			if (count++ > 0) {
				sql.append(", ");
				temp.append(", ");
			}
			sql.append(colName);
			
			Object value = e.getValue();
			if (value instanceof String && isPrimaryKey(colName, pKeys) && ((String)value).endsWith(".nextval")) {
			    temp.append(value);
			} else {
				temp.append("?");
				paras.add(value);
			}
		}
		sql.append(temp.toString()).append(")");
	}

	
	public void forDbUpdate(String tableName, String[] pKeys, Object[] ids, Record record, StringBuilder sql,
			List<Object> paras) {
		tableName = tableName.trim();
		trimPrimaryKeys(pKeys);
		
		sql.append("update ").append(tableName).append(" set ");
		for (Entry<String, Object> e: record.getColumns().entrySet()) {
			String colName = e.getKey();
			if (!isPrimaryKey(colName, pKeys)) {
				if (paras.size() > 0) {
					sql.append(", ");
				}
				sql.append(colName).append(" = ? ");
				paras.add(e.getValue());
			}
		}
		sql.append(" where ");
		for (int i=0; i<pKeys.length; i++) {
			if (i > 0) {
				sql.append(" and ");
			}
			sql.append(pKeys[i]).append(" = ?");
			paras.add(ids[i]);
		}
		
	}

	public boolean isH2() {
		return true;
	}
	
	public void fillStatement(PreparedStatement pst, List<Object> paras) throws SQLException {
		for (int i=0, size=paras.size(); i<size; i++) {
			Object value = paras.get(i);
			if (value instanceof java.sql.Date) {
				pst.setDate(i + 1, (java.sql.Date)value);
			} else if (value instanceof java.sql.Timestamp) {
				pst.setTimestamp(i + 1, (java.sql.Timestamp)value);
			} else {
				pst.setObject(i + 1, value);
			}
		}
	}
	
	public void fillStatement(PreparedStatement pst, Object... paras) throws SQLException {
		for (int i=0; i<paras.length; i++) {
			Object value = paras[i];
			if (value instanceof java.sql.Date) {
				pst.setDate(i + 1, (java.sql.Date)value);
			} else if (value instanceof java.sql.Timestamp) {
				pst.setTimestamp(i + 1, (java.sql.Timestamp)value);
			} else {
				pst.setObject(i + 1, value);
			}
		}
	}
	
	
	public String getDefaultPrimaryKey() {
		return "ID";
	}
}