GitHub项目:jkrasnay/sqlbuilder的使用

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技术选型:

在报表查询时,通常需要做可以动态添加的条件

在老项目中使用的是一种Tcondition的对象分装sql

import java.util.HashMap;

public class TCondition {

    private String sql;

    private Object[] paraValues;

    private String orderBy;

    private String groupBy;

    private String having;

    /**
     * key为表名,value为 left join on后的内容(如何关联的)
     */
    private HashMap leftJoinMap;

    /**
     * count方法计数时可指定 count哪个字段,默认为count(1)
     */
    private String mainId;

    public TCondition() {

    }

    public TCondition(String sql, Object... paraValues) {
        this.setSql(sql);
        this.setParaValues(paraValues);
    }

    public static TCondition of() {
        return new TCondition();
    }

    public static TCondition of(String sql, Object... paraValues) {
        return new TCondition(sql, paraValues);
    }

    public String getSql() {
        return sql;
    }

    public TCondition setSql(String sql) {
        this.sql = sql;
        return this;
    }

    public Object[] getParaValues() {
        return paraValues;
    }

    public TCondition setParaValues(Object[] paraValues) {
        this.paraValues = paraValues;
        return this;
    }

    public String getOrderBy() {
        return orderBy;
    }

    public TCondition setOrderBy(String orderBy) {
        this.orderBy = orderBy;
        return this;
    }

    public String getGroupBy() {
        return groupBy;
    }

    public TCondition setGroupBy(String groupBy) {
        this.groupBy = groupBy;
        return this;
    }

    public String getHaving() {
        return having;
    }

    public TCondition setHaving(String having) {
        this.having = having;
        return this;
    }

    public String getMainId() {
        return mainId;
    }

    public TCondition setMainId(String mainId) {
        this.mainId = mainId;
        return this;
    }

    @Override
    public String toString() {
        StringBuffer result = new StringBuffer(this.getSql() + ":");
        for (int i = 0; i < paraValues.length; i++) {
            result.append(paraValues[i]).append(",");
        }
        result.append(" || ");
        return result.toString();
    }

    public HashMap getLeftJoinMap() {
        return leftJoinMap;
    }

    public TCondition setLeftJoinMap(HashMap leftJoinMap) {
        this.leftJoinMap = leftJoinMap;
        return this;
    }

但是由于与老代码的数据库访问层紧紧的耦合在一起,无法在另外的项目中进行复用,因此,在GitHub中找到了一款类似的封装SQL查询的对象

封装的内容:

package ca.krasnay.sqlbuilder;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * Tool for programmatically constructing SQL select statements. This class aims
 * to simplify the task of juggling commas and SQL keywords when building SQL
 * statements from scratch, but doesn't attempt to do much beyond that. Here are
 * some relatively complex examples:
 *
 * 
 * String sql = new SelectBuilder()
 * .column("e.id")
 * .column("e.name as empname")
 * .column("d.name as deptname")
 * .column("e.salary")
 * .from(("Employee e")
 * .join("Department d on e.dept_id = d.id")
 * .where("e.salary > 100000")
 * .orderBy("e.salary desc")
 * .toString();
 * 
 *
 * 
 * String sql = new SelectBuilder()
 * .column("d.id")
 * .column("d.name")
 * .column("sum(e.salary) as total")
 * .from("Department d")
 * .join("Employee e on e.dept_id = d.id")
 * .groupBy("d.id")
 * .groupBy("d.name")
 * .having("total > 1000000").toString();
 * 
 *
 * Note that the methods can be called in any order. This is handy when a base
 * class wants to create a simple query but allow subclasses to augment it.
 *
 * It's similar to the Squiggle SQL library
 * (http://code.google.com/p/squiggle-sql/), but makes fewer assumptions about
 * the internal structure of the SQL statement, which I think makes for simpler,
 * cleaner code. For example, in Squiggle you would write...
 *
 * 
 * select.addCriteria(new MatchCriteria(orders, "status", MatchCriteria.EQUALS, "processed"));
 * 
 *
 * With SelectBuilder, we assume you know how to write SQL expressions, so
 * instead you would write...
 *
 * 
 * select.where("status = 'processed'");
 * 
 *
 * To include parameters, it's highly recommended to use the
 * {@link ParameterizedPreparedStatementCreatorTest}, like this:
 *
 * 
 * String sql = new SelectBuilder("Employee e")
 * .where("name like :name")
 * .toString();
 *
 * PreparedStatement ps = new ParameterizedPreparedStatementCreator(sql)
 * .setParameter("name", "Bob%")
 * .createPreparedStatement(conn);
 * 
 *
 *
 * @author John Krasnay 
 */
public class SelectBuilder extends AbstractSqlBuilder implements Cloneable, Serializable {

    private static final long serialVersionUID = 1;

    private boolean distinct;

    private List