1. SQL查詢的統(tǒng)一抽象

?MyBatis制動動態(tài)SQL的構(gòu)造,利用動態(tài)SQL和自定義的參數(shù)Bean抽象,可以將絕大部分SQL查詢抽象為一個統(tǒng)一接口,查詢參數(shù)使用一個自定義bean繼承Map,使用映射的方法構(gòu)造多查詢參數(shù).在遇到多屬性參數(shù)(例如order by,其參數(shù)包括列名,升序降序類型,以及可以多個列及升降序類型憑借在order by之后)無法使用簡單的key-value表示時,可以將參數(shù)單獨(dú)抽象為一個類.

將要用到的bean

package com.xxx.mybatistask.bean;import com.xxx.mybatistask.support.jsonSerializer.JsonDateDeserializer; import com.xxx.mybatistask.support.jsonSerializer.JsonDateSerializer; import org.codehaus.jackson.map.annotate.JsonDeserialize; import org.codehaus.jackson.map.annotate.JsonSerialize;import java.util.Date;public class Post {private int id;private String title;private String content;private String author;private PostStatus status;private Date created;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public PostStatus getStatus() {return status;}public void setStatus(PostStatus status) {this.status = status;}@JsonSerialize(using = JsonDateSerializer.class)public Date getCreated() {return created;}@JsonDeserialize(using = JsonDateDeserializer.class)public void setCreated(Date created) {this.created = created;} }

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1)參數(shù)Bean設(shè)計

總的參數(shù)Map抽象接口設(shè)計

package com.xxx.mybatistask.bean.query;import java.util.Map;public interface QueryParam extends Map<String, Object> {/*** 新增查詢參數(shù)** @param key 參數(shù)名* @param value 參數(shù)值* @return*/QueryParam fill(String key, Object value); }

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列表查詢參數(shù)接口

package com.xxx.mybatistask.bean.query;import java.util.List;public interface ListQueryParam extends QueryParam {/*** 獲取排序條件集合** @return*/List<SortCond> getSortCond();/*** 添加排序條件** @param sortCond*/void addSortCond(SortCond sortCond);void addSortCond(List<SortCond> sortCondList);/*** 獲取當(dāng)前頁數(shù)** @return*/Integer getPage();/*** 獲取每頁查詢記錄數(shù)** @return*/Integer getPageSize();/*** 設(shè)置當(dāng)前頁數(shù)*/void setPage(Integer page);/*** 設(shè)置每頁查詢記錄數(shù)*/void setPageSize(Integer pageSize); }

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列表查詢參數(shù)接口實(shí)現(xiàn)

package com.xxx.mybatistask.bean.query;import java.util.LinkedHashMap; import java.util.LinkedList; import java.util.List;public class GenericQueryParam extends LinkedHashMap<String, Object> implements ListQueryParam {/*** 最大單頁記錄數(shù)*/public final static int MAX_PAGE_SIZE = 100;/*** 當(dāng)前頁面key*/private final static String PAGE_KEY = "__page";/*** 單頁記錄數(shù)key*/private final static String PAGESIZE_KEY = "__pagesize";/*** 排序參數(shù)List key*/private final static String SORTCOND_KEY = "__sortcond";public GenericQueryParam() {this(1, 10);}public GenericQueryParam(Integer page,Integer pageSize) {setPage(page);setPageSize(pageSize);}@Overridepublic Integer getPage() {return (Integer) get(PAGE_KEY);}@Overridepublic Integer getPageSize() {return (Integer) get(PAGESIZE_KEY);}@Overridepublic void setPage(Integer page) {put(PAGE_KEY, page);}@Overridepublic void setPageSize(Integer pageSize) {put(PAGESIZE_KEY, pageSize);}@Override@SuppressWarnings("unchecked")public List<SortCond> getSortCond() {List<SortCond> sortCondList = (List<SortCond>) get(SORTCOND_KEY);if (sortCondList == null) {sortCondList = new LinkedList<SortCond>();put(SORTCOND_KEY, sortCondList);}return sortCondList;}@Override@SuppressWarnings("unchecked")public void addSortCond(SortCond sortCond) {List<SortCond> sortCondList = (List<SortCond>) get(SORTCOND_KEY);if (sortCondList == null) {sortCondList = new LinkedList<SortCond>();put(SORTCOND_KEY, sortCondList);}sortCondList.add(sortCond);}@Overridepublic void addSortCond(List<SortCond> sortCondList) {for (SortCond sortCond : sortCondList) addSortCond(sortCond);}@Overridepublic QueryParam fill(String key, Object value) {put(key, value);return this;} }

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排序參數(shù)的抽象

package com.xxx.mybatistask.bean.query;public class SortCond {/*** 排序類型枚舉*/public enum Order {ASC, DESC}/*** 排序類型*/private String column;/*** 排序類型*/private Order order;public SortCond(String column) {this(column, Order.DESC);}public SortCond(String column, Order order) {this.column = column;this.order = order;}public String getColumn() {return column;}public Order getOrder() {return order;} }

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2)Service查詢接口設(shè)計

package com.xxx.mybatistask.service;import com.xxx.mybatistask.bean.query.GenericQueryParam; import org.apache.ibatis.session.SqlSession; import org.slf4j.Logger; import org.slf4j.LoggerFactory;import javax.annotation.Resource;public abstract class AbstractService {protected final Logger logger = LoggerFactory.getLogger(getClass());@Resourceprotected SqlSession sqlSession;/*** 分頁參數(shù)校驗(yàn)** @param params* @param rowCount* @return*/protected void pageParamValidate(GenericQueryParam params, int rowCount) {int page = params.getPage();int pageSize = params.getPageSize();if (page < 1) page = 1;if (pageSize < 1) pageSize = 1;if (pageSize > GenericQueryParam.MAX_PAGE_SIZE)pageSize = GenericQueryParam.MAX_PAGE_SIZE;int maxPage = (int) Math.ceil((double) rowCount / pageSize);if (page > maxPage) page = maxPage;params.setPage(page);params.setPageSize(pageSize);} }

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package com.xxx.mybatistask.service;import com.xxx.mybatistask.bean.Post; import com.xxx.mybatistask.bean.query.GenericQueryParam; import com.xxx.mybatistask.bean.query.ListResult;public interface PostService {/*** 查詢參數(shù)列名枚舉*/public enum PostQueryPram {title, content, author, status, created}void create(Post post);/*** 翻頁查詢** @param param* @return*/ListResult<Post> select(GenericQueryParam param);void update(Post post); }

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package com.xxx.mybatistask.service.impl;import com.xxx.mybatistask.bean.Post; import com.xxx.mybatistask.bean.query.GenericQueryParam; import com.xxx.mybatistask.bean.query.ListResult; import com.xxx.mybatistask.service.AbstractService; import com.xxx.mybatistask.service.PostService; import org.apache.ibatis.session.RowBounds; import org.springframework.stereotype.Service;import java.util.LinkedList; import java.util.List;@Service public class PostServiceImpl extends AbstractService implements PostService {@Overridepublic void create(Post post) {sqlSession.insert("post.insert", post);}@Overridepublic ListResult<Post> select(GenericQueryParam params) {Integer rowCount = sqlSession.selectOne("post.selectCount", params);if (rowCount == 0) {return new ListResult<Post>(new LinkedList<Post>(), 0);}// 分頁參數(shù)檢查 pageParamValidate(params, rowCount);int page = params.getPage();int pageSize = params.getPageSize();int offset = (page - 1) * pageSize;RowBounds rowBounds = new RowBounds(offset, pageSize);List<Post> postList = sqlSession.selectList("post.select", params, rowBounds);return new ListResult<Post>(postList, rowCount);}@Overridepublic void update(Post post) {sqlSession.update("post.update", post);} }

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3)自定義參數(shù)bean的解析與轉(zhuǎn)換

以SortCond為例,由于是多屬性查詢參數(shù),所以我們需要自己定義參數(shù)在客戶端的文本格式,從客戶端傳入后再使用自定義的Paser來將其包裝成SortCond

例如此處我們定義的排序參數(shù)在url中的格式為

/api/post/query/title/an?page=3&pageSize=200&sorts=created:DESC|author:ASC

其中排序參數(shù)為 "created:DESC|author:ASC" , 解析類如下

package com.xxx.mybatistask.support.stringparser;import java.util.List;public interface Parser<T> {/*** 字符串轉(zhuǎn)對象** @param parseString 待轉(zhuǎn)換字符串* @return List<T> 轉(zhuǎn)換完成的對象List*/List<T> parseList(String parseString); }

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package com.xxx.mybatistask.support.stringparser;import com.google.common.base.Splitter; import com.google.common.collect.Lists; import com.xxx.mybatistask.bean.query.SortCond;import java.util.List; import java.util.Map;public class SortCondParser implements Parser<SortCond> {/*** 排序列分隔符*/private static final String COL_SPLITTER = "|";/*** 順序類型分隔符*/private static final String ORDER_SPLITTER = ":";/*** 列名檢查*/private Class<? extends Enum> columnEnumCls;public SortCondParser(Class<? extends Enum> columnEnumCls) {this.columnEnumCls = columnEnumCls;}/*** 將字符串轉(zhuǎn)換為SortCond* 字符串的標(biāo)準(zhǔn)格式為* title:ASC|created:DESC** @param parseString 待轉(zhuǎn)換字符串* @return*/@Overridepublic List<SortCond> parseList(String parseString) {List<SortCond> sortCondList = Lists.newArrayList();// 將字符串切分為 {"column" => "order"} 的形式Map<String, String> sortOrderMap =Splitter.on(COL_SPLITTER).trimResults().omitEmptyStrings().withKeyValueSeparator(ORDER_SPLITTER).split(parseString);String column = null;String order = null;for (Map.Entry<String, String> entry : sortOrderMap.entrySet()) {// 驗(yàn)證column合法性column = entry.getKey();if (column != null && !column.equals("")) {Enum.valueOf(columnEnumCls, column);} else {break;}// 驗(yàn)證order合法性order = entry.getValue();if (order != null && !order.equals("")) {Enum.valueOf(SortCond.Order.class, order);} else {order = SortCond.Order.DESC.name();}sortCondList.add(new SortCond(column, SortCond.Order.valueOf(order)));}return sortCondList;} }

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4) 動態(tài)查詢SQL的編寫

<select id="select"parameterType="com.xxx.mybatistask.bean.query.GenericQueryParam"resultType="com.xxx.mybatistask.bean.Post"><![CDATA[selectid,title,content,author,status,createdfrompost]]><where><if test="id != null">and id = #{id}</if><if test="title != null and title != ''">and title like concat('%', #{title}, '%')</if><if test="author != null and author != ''">and author like concat('%', #{author}, '%')</if><if test="content != null and content != ''">and match(content) against(#{content})</if><if test="status != null">and status = #{status}</if><if test="created != null and created != ''">and created = #{created}</if></where><if test="_parameter.getSortCond().size() != 0">order by<foreach collection="_parameter.getSortCond()" item="sortCond" separator=",">${sortCond.column} ${sortCond.order}</foreach></if></select>

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至此SQL抽象接口以及完成,結(jié)合SortCond類,動態(tài)SQL和OGNL動態(tài)生成了order by參數(shù),而類似的像 JOIN ... ON (USING) 或者 GROUP BY ... HAVING 等查詢參數(shù)條件,也可以將其抽象成bean,通過GenericQueryParam成員變量的形式拼接到SQL查詢語句中來

另外代碼中并沒有對參數(shù)進(jìn)行過多的檢查,原因是:

1. MyBatis SQL查詢使用prepareStatement,對于注入問題相對安全

2. 動態(tài)SQL查詢使用<if>判斷where查詢條件,如果參數(shù)中的map key不是有效列名,將不會拼接到SQL語句中

3. 即使由于惡意用戶篡改參數(shù)格式造成不規(guī)范參數(shù)的SQL查詢異常,對于這種異常只需要重定向到全局error頁面即可

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5) Controller調(diào)用示例

@RequestMapping(value = "/query/{colKey}/{colVal}", method = RequestMethod.GET)public@ResponseBodyObject query(@PathVariable String colKey,@PathVariable String colVal,@RequestParam(value = "status", required = false) String status,@RequestParam(value = "page", required = false, defaultValue = "1") Integer page,@RequestParam(value = "pageSize", required = false, defaultValue = "10") Integer pageSize,@RequestParam(value = "sorts", required = false, defaultValue = "") String sorts) {// page and colGenericQueryParam params = new GenericQueryParam(page, pageSize);params.fill(colKey, colVal).fill(PostService.PostQueryPram.status.name(),PostStatus.valueOf(status));// sortsSortCondParser sortCondParser = new SortCondParser(PostService.PostQueryPram.class);params.addSortCond(sortCondParser.parseList(sorts));ListResult<Post> postList = postService.select(params);return dataJson(postList);}

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2. TypeHandler設(shè)計

上文中的bean Post類中status屬性類型是enum類,如下

package com.xxx.mybatistask.bean;public enum PostStatus {NORMAL(0, "正常"), LOCKED(1, "鎖定");private int code;private String text;private PostStatus(int code, String text) {this.code = code;this.text = text;}public int code() {return code;}public String text() {return text;}public static PostStatus codeOf(int code) {for (PostStatus postStatus : PostStatus.values()) {if (postStatus.code == code) {return postStatus;}}throw new IllegalArgumentException("invalid code");}public static boolean contains(String text) {for (PostStatus postStatus : PostStatus.values()) {if (postStatus.toString().equals(text)) {return true;}}return false;} }

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而這個屬性在數(shù)據(jù)庫中的類型實(shí)際上市一個tinyint表示的標(biāo)記位,為了讓mybatis jdbc自動轉(zhuǎn)換這個tinyint標(biāo)記位為enum(查詢時)和轉(zhuǎn)換enum為tinyint(插入更新時),需要編寫mybatis typehandler

package com.xxx.mybatistask.support.typehandler;import com.xxx.mybatistask.bean.PostStatus; import org.apache.ibatis.type.JdbcType; import org.apache.ibatis.type.TypeHandler;import java.sql.CallableStatement; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException;public class PostStatusTypeHandler implements TypeHandler<PostStatus> {/*** PostStatus插入數(shù)據(jù)庫時轉(zhuǎn)換的方法* 將使用PostStatus的code插入數(shù)據(jù)庫** @param preparedStatement* @param index* @param postStatus* @param jdbcType* @throws SQLException*/@Overridepublic void setParameter(PreparedStatement preparedStatement, int index, PostStatus postStatus, JdbcType jdbcType) throws SQLException {preparedStatement.setInt(index, postStatus.code());}/*** status查詢出來時轉(zhuǎn)為PostStatus的方法** @param resultSet* @param colName* @return* @throws SQLException*/@Overridepublic PostStatus getResult(ResultSet resultSet, String colName) throws SQLException {return PostStatus.codeOf(resultSet.getInt(colName));}@Overridepublic PostStatus getResult(ResultSet resultSet, int colIndex) throws SQLException {return PostStatus.codeOf(resultSet.getInt(colIndex));}@Overridepublic PostStatus getResult(CallableStatement callableStatement, int colIndex) throws SQLException {return PostStatus.codeOf(callableStatement.getInt(colIndex));} }

在MyBatis配置文件中配置這個TypeHandler是其對PostStatus參數(shù)生效

<typeHandlers><typeHandler handler="com.xxx.mybatistask.support.typehandler.PostStatusTypeHandler"javaType="com.xxx.mybatistask.bean.PostStatus"/></typeHandlers>

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3. 特殊參數(shù)的序列化與反序列化

由于需要實(shí)現(xiàn)接收和響應(yīng)JSON數(shù)據(jù),自動將JSON數(shù)據(jù)包裝為具體對象類,此處使用了Spring的@ResponseBody以及@RequestBody標(biāo)簽,JSON的轉(zhuǎn)換器為org.codehaus.jackson

但是對于某些特殊屬性,例如此處的Post里的created屬性,在bean中表現(xiàn)為Date類型,而在數(shù)據(jù)庫中為TIMESTAMP類型,如果直接輸出到JSON響應(yīng)中,將會輸出timestamp的毫秒數(shù),為了格式化為自定義的格式,我們需要自定義一個JSON序列化(轉(zhuǎn)為響應(yīng)文本時)與反序列化(接收請求參數(shù)轉(zhuǎn)為POST類時)的類.如下

序列化類

package com.xxx.mybatistask.support.jsonSerializer;import org.codehaus.jackson.JsonGenerator; import org.codehaus.jackson.JsonProcessingException; import org.codehaus.jackson.map.JsonSerializer; import org.codehaus.jackson.map.SerializerProvider;import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date;public class JsonDateSerializer extends JsonSerializer<Date> {private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");@Overridepublic void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {jsonGenerator.writeString(sdf.format(date));} }

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反序列化類

package com.xxx.mybatistask.support.jsonSerializer;import org.codehaus.jackson.JsonNode; import org.codehaus.jackson.JsonParser; import org.codehaus.jackson.ObjectCodec; import org.codehaus.jackson.map.DeserializationContext; import org.codehaus.jackson.map.JsonDeserializer;import java.io.IOException; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date;public class JsonDateDeserializer extends JsonDeserializer<Date> {private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");@Overridepublic Date deserialize(JsonParser jsonParser,DeserializationContext deserializationContext)throws IOException {ObjectCodec oc = jsonParser.getCodec();JsonNode node = oc.readTree(jsonParser);try {return sdf.parse(node.getTextValue());} catch (ParseException e) {e.printStackTrace();}return null;} }

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然后注意在Post類中標(biāo)明,當(dāng)Jackson序列化Post類為JSON串或?qū)SON串反序列化成Post類時,將調(diào)用這兩個類,Post類的代碼片段

@JsonSerialize(using = JsonDateSerializer.class)public Date getCreated() {return created;}@JsonDeserialize(using = JsonDateDeserializer.class)public void setCreated(Date created) {this.created = created;}

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THE END

轉(zhuǎn)載于:https://www.cnblogs.com/zemliu/p/3248171.html

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