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 -->
