Ofbiz项目学习——阶段性小结——查询

一、组装参数的学习

首先是查询条件，对于查询条件，需要判断是否从前端传递空值？——怎么处理查询空值？

当然可以一个一个进行判断，但是这样代码会导致很多，可以统一处理，形成一个公共方法。

1、 单个处理的方式：

　　调用工具方法判空（底层：判断是否是null 和空）

/** UtilValidate类. */

/** Check whether string s is NOT empty. */
public static boolean isNotEmpty(String s) {
return (s != null) && s.length() > 0;
}

/** Check whether collection c is NOT empty. */
public static <E> boolean isNotEmpty(Collection<E> c) {
return (c != null) && !c.isEmpty();
}

/** Check whether charsequence c is NOT empty. */
public static <E> boolean isNotEmpty(CharSequence c) {
return ((c != null) && (c.length() > 0));
}

        if (UtilValidate.isNotEmpty(startDate)) {
            condList.add(EntityCondition.makeCondition(PackagePrepayFields.REPAY_APP_DATE,
                    EntityOperator.GREATER_THAN_EQUAL_TO,
                    startDate));
        }

 2、多个处理：

　　多个处理需要知道最终需要的是什么数据结构。反向推导

    /** Set a list of EntityCondition objects to be ANDed together as the WHERE clause for the query
     * 
     * NOTE: Each successive call to any of the where(...) methods will replace the currently set condition for the query.
     * @param fieldMap - A list of EntityCondition objects to be ANDed together as the WHERE clause for the query
     * @return this EntityQuery object, to enable chaining
     */
    public <T extends EntityCondition> EntityQuery where(List<T> andConditions) {
        this.whereEntityCondition = EntityCondition.makeCondition(andConditions);
        return this;
    }

从上面的API中，可以看到需要的是List<T>，T必须是EntityCondition的子类或者其本身，暂时先使用EntityCondition，所以返回是List<EntityCondition>。

    /**
     * 封装查询条件列表
     * 
     * @param arr
     * @param context 入参上下文
     * @author  
     */
    public static List<EntityCondition> setConditions(String[] arr, Map<String, ? extends Object> context) {
        if (arr == null || arr.length <= 0) {
            return null;
        }
        List<EntityCondition> conditionList = new LinkedList<EntityCondition>();
        for (int i = 0; i < arr.length; i++) {
            if (context.get(arr[i]) != null && !context.get(arr[i]).equals("")) {
                conditionList.add(EntityCondition.makeCondition(arr[i], context.get(arr[i])));
            }
        }
        return conditionList;
    }

上述方法中EntityCondition.makeCondition(arr[i],context.get(arr[i]))调用的API如下：

public static <R> EntityExpr makeCondition(String fieldName, R value) {
        return new EntityExpr(fieldName, EntityOperator.EQUALS, value);
    }

但是针对非EntityOperator.EQUALS的查询条件，需要自己写。

    public static <L,R,LL,RR> EntityExpr makeCondition(L lhs, EntityComparisonOperator<LL,RR> operator, R rhs) {
        return new EntityExpr(lhs, operator, rhs);
    }

 3、分页处理

        Integer viewIndex = ToolsUtil.paraseObjToInteger(context.get(PackagePrepayFields.VIEW_INDEX), 1);
        Integer viewSize = ToolsUtil.paraseObjToInteger(context.get(PackagePrepayFields.VIEW_SIZE), 20);

    /**
     * 将Object对象转换为Integer
     *
     * @param obj
     * @param def
     * @return
     * @author  
     */
    public static Integer paraseObjToInteger(Object obj, Integer def) {
        if (obj == null || "null".equals(obj)) {
            return def;
        }
        try {
            return Integer.parseInt(obj.toString());
        } catch (Exception e) {
            throw new RuntimeException("Object{" + obj.toString() + "} parase to Decimal exception!", e);
        }
    }

再次，是查询要展示的列，查看API，提供两种方式

    /** Set the fields to be returned when the query is executed.
     * 
     * Note that the select methods are not additive, if a subsequent 
     * call is made to select then the existing fields for selection 
     * will be replaced.
     * @param fieldsToSelect - A Set of Strings containing the field names to be selected
     * @return this EntityQuery object, to enable chaining
     */
    public EntityQuery select(Set<String> fieldsToSelect) {
        this.fieldsToSelect = fieldsToSelect;
        return this;
    }

    /** Set the fields to be returned when the query is executed.
     * 
     * Note that the select methods are not additive, if a subsequent 
     * call is made to select then the existing fields for selection 
     * will be replaced.
     * @param fieldsToSelect - Strings containing the field names to be selected
     * @return this EntityQuery object, to enable chaining
     */
    public EntityQuery select(String...fields) {
        this.fieldsToSelect = UtilMisc.toSetArray(fields);
        return this;
    }

鉴于此代码，包装的更多，使用更简单，public EntityQuery select(String...fields)

String[] columns =
                {PackagePrepayFields.CUST_NO, PackagePrepayFields.CUST_NAME, PackagePrepayFields.VEHICLE_NO,
                        PackagePrepayFields.PLATE_NO, PackagePrepayFields.DOC_NO, PackagePrepayFields.SALE_NAME,
                        PackagePrepayFields.PENTY_AMT, PackagePrepayFields.PENTY_DEDUCT, PackagePrepayFields.PRIN_AMT,
                        PackagePrepayFields.AHEAD_AMT, PackagePrepayFields.PAY_MODE, PackagePrepayFields.MAIL_ADDRESS,
                        PackagePrepayFields.REPAY_APP_DATE, PackagePrepayFields.REPAY_APP_STATUS,
                        PackagePrepayFields.OPER_NO, PackagePrepayFields.RET_MSG, PackagePrepayFields.REMARK};

当然，我们如果开发过程中，需要再多个地方使用，这块可以提取出来，作为公共方法。

最后我们看一下查询的方法

PagedList<GenericValue> pagedList = EntityQuery.use(delegator)
                    .select(columns)
                    .from(PackagePrepayFields.COM_MESSAGE_INFO_TEXT_THREE)
                    .where(condList)
                    .cursorScrollInsensitive()
                    .queryPagedList(viewIndex - 1, viewSize);
            result.put("list", pagedList.getData());
            result.put("totalSize", pagedList.getSize());

比较一下不分页的

// 不带分页
List<GenericValue> list =EntityQuery.use(delegator)
                    .select(columns) 
                    .from(PackagePrepayFields.COM_MESSAGE_INFO_TEXT_THREE)
                    .where(condList)
                    .queryList();

顺便看一下服务（方法名称）对应XML的配置

　　入参

<attribute name="viewSize" type="Integer" mode="IN"  optional="true" description="条数" />
<attribute name="viewIndex" type="Integer" mode="IN"  optional="true" description="页码" />

　　出参

<attribute name="returnCode" type="Map" mode="OUT" optional="true" description="标准返回状态数据"/>
<attribute name="totalSize" type="Integer" mode="OUT"  optional="true" description="返回总条数" /> <--此处注意出参的大小写 -->