controller需要到½W¬ä¸€æ¡ä¿¡æ¯å°±æ˜¯æ€»è¡Œæ•°ã€?/p>

public int getTotalPresidents(FilterSet filterSet, boolean isExported) {

String totalQuery = presidentsDao.getTotalPresidentsQuery();

String modTotalQuery = filterQuery(filterSet, totalQuery);

int totalRows = presidentsDao.getTotalPresidents(modTotalQuery);

if (isExported && totalRows > maxExportRows) {

totalRows = maxExportRows;

}

return totalRows;

}

serviceå’Œdao一èµäh¥˜q‡æ×o¾l“果集，它的工作方式是在Where语句后面增加更多的AND语句来修æ”ÒŽŸ¥è¯¢å­—½W¦ä¸²ã€‚äؓ此，你需要和Limit FilterSet一起工作ã€?/p>

FilterSet是一个过滤器对象数组åQŒä¸€ä¸ªè¿‡æ»¤å™¨åŒ…括一个bean property和这个过滤器的倹{€‚或者，½Ž€å•çš„说就是用æˆähƒ³è¦è¿‡æ»¤çš„行和他们输入的倹{€‚这使得它非常容易交互。service只需要è„P代所有的 FilterSetòq¶è°ƒç”¨dao来拼接查询语句。（译者注åQšè¿‡æ»¤çš„实现方式是：在Where后面增加And语句来改变查询语句以辑ֈ°å¯ÒŽ•°æ®è¿›è¡Œè¿‡æ»¤çš„效果åQ?/p>

private String filterQuery(FilterSet filterSet, String query) {

if (!filterSet.isFiltered() || filterSet.isCleared()) {

return query;

}



Filter filters[] = filterSet.getFilters();

for (int i = 0; i < filters.length; i++) {

Filter filter = filters[i];

String property = filter.getProperty();

String value = filter.getValue();

query = presidentsDao.filterQuery(query, property, value);

}



return query;

}

query修改包括了filter信息åQŒæ€»è¡Œæ•°ã€‚在一些情况下˜q™å°±­‘›_¤ŸåQŒä½†æ˜¯å½“用户导出数据时仍然存在一个潜在的问题。äؓ了保持高æ•?service不允许导å‡ø™¶…å‡ÞZ¸€ä¸ªæœ€å¤§è¡Œæ•°çš„数据ã€?/p>

controller需要到½W¬äºŒæ¡ä¿¡æ¯å°±æ˜¯Collectionã€?/p>

public Collection getPresidents(FilterSet filterSet, Sort sort, int rowEnd) {

String patientsQuery = presidentsDao.getPresidentsQuery();

String modPatientsQuery = filterQuery(filterSet, patientsQuery);

modPatientsQuery = sortQuery(sort, modPatientsQuery);

modPatientsQuery = presidentsDao.limitQuery(rowEnd, modPatientsQuery);

return presidentsDao.getPresidents(modPatientsQuery);

}

和前面一æ øP¼Œserviceå’Œdao一èµäh¥˜q‡æ×o¾l“果集ã€?/p>

另外query字符串需要扩展ORDER BY语句以便数据按照正确的方式进行排序。Sort包含一个bean propertyå’?sortOrderå€û|¼ˆæ­£åº˜q˜æ˜¯é€†åºåQ‰ã€‚service仅仅需要ä‹É用Sort来调用daoã€?/p>

private String sortQuery(Sort sort, String query) {

if (!sort.isSorted()) {

String defaultSortOrder = presidentsDao.getDefaultSortOrder();

if (StringUtils.isNotBlank(defaultSortOrder)) {

return query + defaultSortOrder;

}



return query;

}



String property = sort.getProperty();

String sortOrder = sort.getSortOrder();



return presidentsDao.sortQuery(query, property, sortOrder);

}

query字符串最后需要的修改ž®±æ˜¯å¢žåŠ æ•°æ®åº“特别的指ä×o来limitž®†è¦è¢«è¿”回的¾l“果集。这ž®±æ˜¯limitQuery() æ–ÒŽ³•çš„作用ã€?/p>

ä¸ÞZº†çœŸæ­£ç†è§£daoåQŒquery字符串需要被展示ã€?/p>

˜q™å°±æ˜¯å¾—到数据的presidents query字符ä¸ÔŒ¼š

private final static String presidentsQuery = 

" SELECT " +

"    president_id presidentId, " + 

"    first_name firstName, " +

"    last_name lastName, " +

"    nick_name nickName,  " +

"    concat(first_name, ' ',last_name) fullName, " +

"    term,  " +

"    born,  " +

"    died,  " +

"    education, " + 

"    career,  " +

"    political_party politicalParty " +

" FROM presidents ";

˜q™æ˜¯å¾—到总行数的query字符ä¸ÔŒ¼š

private final static String totalPresidentsQuery = 

" SELECT count(*) FROM presidents ";

两个最有趣的方法就是过滤和排序�/p>

filter看è“v来像˜q™æ ·åQ?/p>

public String filterQuery(String query, String property, String value) {

StringBuffer result = new StringBuffer(query);



if (query.indexOf("WHERE") == -1) {

result.append(" WHERE 1 = 1 "); //stub WHERE clause so can just append AND clause

}



if (property.equals("fullName")) {

result.append(" AND concat(first_name, ' ',last_name) like '%" + value + "%'");

} else if (property.equals("nickName")) {

result.append(" AND nick_name like '%" + value + "%'");

} else {

result.append(" AND " + property + " like '%" + value + "%'");

}



return result.toString();

}

filterQuery()æ–ÒŽ³•éœ€è¦å¢žåŠ æ­£¼‹®çš„AND语句到query字符丌Ӏ?/p>

sort看è“v来非常类ä¼û|¼š

public String sortQuery(String query, String property, String sortOrder) {

StringBuffer result = new StringBuffer(query + " ORDER BY ");



if (property.equals("fullName")) {

result.append("concat(first_name, ' ',last_name) " + sortOrder);

} else {

result.append(property + " " + sortOrder);

}



return result.toString();

}

sortQuery()æ–ÒŽ³•éœ€è¦å¢žåŠ æ­£¼‹®çš„ORDER BY语句到query字符丌Ӏ?/p>

现在query字符串修改能够正¼‹®çš„˜q›è¡Œfilterå’ŒsortåQŒå®ƒ˜q˜éœ€è¦ä¿®æ”¹ä»¥ä¾¿åªå–页面显½Cºç›¸å…³çš„数据。MySQL为s the limit命ä×oã€?/p>

public String limitQuery(int rowEnd, String query) {

return query + " limit " + rowEnd;

}

service需要的唯一东西ž®±æ˜¯åQšæ€»è¡Œæ•°å’ŒCollectionã€?/p>

public Collection getPresidents(final String query) {

return jdbcTemplate.query(query, new ResultReader() {

List results = new ArrayList();

public List getResults() {

return results;

}



public void processRow(ResultSet rs)

throws SQLException {

President president = new President();

president.setPresidentId(new Integer(rs.getInt("presidentId")));

president.setFirstName(rs.getString("firstName"));

president.setLastName(rs.getString("lastName"));

president.setNickName(rs.getString("nickName"));

president.setFullName(rs.getString("fullName"));

president.setTerm(rs.getString("term"));

president.setBorn(rs.getDate("born"));

president.setDied(rs.getDate("died"));

president.setEducation(rs.getString("education"));

president.setCareer(rs.getString("career"));

president.setPoliticalParty(rs.getString("politicalParty"));

results.add(president);

}

});        

}



public int getTotalPresidents(final String query) {

return jdbcTemplate.queryForInt(query);

}

ResultReader是一个帮助处理JDBC查询的Springç‰ÒŽ®Š¾c»ï¼Œä½œäؓ一个callback来处理JDBC ResultSet。jdbcTemplate是对JDBC˜qžæŽ¥çš„抽象ã€?/p>

最后，˜q™æ˜¯service需要的默认sort™åºåºåQ?/p>

public String getDefaultSortOrder() {

return " ORDER BY concat(first_name, ' ', last_name) ";        

}