CriteriaGroup.java

package com.github.walker.easydb.criterion;

import com.github.walker.easydb.exception.CriteriaException;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Vector;

/**
 * 复合表达式类
 *
 * @author HuQingmiao
 */
public class CriteriaGroup extends Criteria {

    public final static String and = "AND";

    public final static String or = "OR";

    private static HashSet<String> opSet = new HashSet<String>(4);

    static {
        opSet.add(and);
        opSet.add(or);
    }

    private Vector<Criteria> vec = new Vector<Criteria>(5);

    private String op;// 运算符

    /**
     * 构造条件组
     *
     * @param operator 二元运算符, 如 "AND","OR"
     */
    public CriteriaGroup(String operator) {
        operator = operator.toUpperCase();

        // CriteriaGroup只支持如下运算符:'AND','OR' 。
        if (!opSet.contains(operator)) {
            new CriteriaException(CriteriaException.NOT_SUPPORTED_OP, "");
        }

        this.op = operator;
    }

    /**
     * 添加子条件
     *
     * @param c 子条件表达示
     */
    public CriteriaGroup add(Criteria c) throws CriteriaException {
        if (c == this) {
            throw new CriteriaException(CriteriaException.CANNOT_ADD_THIS, "");
        }
        vec.add(c);
        return this;
    }

    /**
     * 删除子条件
     *
     * @param c 子条件表达示
     */
    public CriteriaGroup remove(Criteria c) throws CriteriaException {
        if (!vec.contains(c)) {
            throw new CriteriaException(CriteriaException.REMOVE_NOTEXIST, "");
        }
        vec.remove(c);
        return this;
    }

    /**
     * 取得表达式中操作符左边字符串对应的值
     *
     * @param left 表达式中操作符左边的字符串
     * @return 表达式左边字符串对应的值
     */
    public String getValueByLeft(String left) {

        String upColName = left.toUpperCase();

        for (Iterator<Criteria> it = vec.iterator(); it.hasNext(); ) {
            Criteria c = it.next();
            if (c instanceof SimpleExpression) {
                SimpleExpression c1 = (SimpleExpression) c;
                // if the operator is '=', and the column name equals the
                // parameter
                if (c1.getOp().equals("=") && c1.getLeft().equals(upColName)) {
                    return c1.getValue();
                }
            } else if (c instanceof CriteriaGroup) {
                CriteriaGroup cg = (CriteriaGroup) c;

                // 只有条件组的操作符为AND,才能取得某列的精确值
                if (cg.op.equals(CriteriaGroup.and)) {
                    String value = cg.getValueByLeft(left);
                    if (value != null) {
                        return value;
                    }
                }
            }
        }
        return null;
    }

    public String toSqlString() {
        StringBuffer buff = new StringBuffer();
        buff.append("(");

        for (Iterator<Criteria> it = vec.iterator(); it.hasNext(); ) {
            Criteria c = it.next();
            buff.append(c.toString()).append(" ");
            buff.append(this.op).append(" ");
        }

        // 删除最后的操作符及其前后空格
        if (buff.indexOf(this.op) > 0) {
            buff.delete(buff.length() - this.op.length() - 2, buff.length());
        }

        buff.append(")");

        return buff.toString();
    }

}