查询生成器

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public class QueryBuilderVelocity implements QueryBuilder, ApplicationContextAware {    /** logger */    private static final Logger  logger = LoggerFactory.getLogger(QueryBuilderVelocity.class);    /** Velocity引擎 */    protected VelocityEngine     velocityEngine;    /** Spring上下文 */    protected ApplicationContext applicationContext;        public String getQueryString(String queryName, Map<String, ?> conditions) {        String queryTemplate = (String) this.applicationContext.getBean(queryName);        if (queryTemplate == null) {            throw new AppException(ErrorCode.ERROR_QUERY_TEMPLATE_NOT_EXIST, "查询模板不存在！");        }        try {            Context context = new VelocityContext(conditions);            StringWriter queryStringWriter = new StringWriter();            this.velocityEngine.evaluate(context, queryStringWriter, "", queryTemplate);            return queryStringWriter.toString();        } catch (Exception ex) {            logger.error("Velocity引擎生成查询语句出错！", ex);            throw new AppException(ErrorCode.ERROR_BUILD_QUERY_STRING, "Velocity引擎生成查询语句出错！", ex);        }    }    /**     * 设置Velocity引擎     * @param velocityEngine Velocity引擎     */    public void setVelocityEngine(VelocityEngine velocityEngine) {        this.velocityEngine = velocityEngine;    }    /**     * 设置Spring上下文     * @param applicationContext Spring上下文     */    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {        this.applicationContext = applicationContext;    }}
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