mybatisplus 的SQL攔截器實現(xiàn)關(guān)聯(lián)查詢功能
由于項目中經(jīng)常會使用到一些簡單地關(guān)聯(lián)查詢,但是mybatisplus還不支持關(guān)聯(lián)查詢,不過在看官方文檔的時候發(fā)現(xiàn)了mybatisplus的SQL攔截器(其實也是mybatis的)就想著能不能在SQL執(zhí)行的時候做一些處理以至于可以支持關(guān)聯(lián)查詢,于是就動手開始了,目前還只是一個初步的demo,但是一些基本的關(guān)聯(lián)查詢功能經(jīng)過驗證是沒有問題的
環(huán)境信息
jdk: 1.8
springboot: 2.3.4.RELEASE
mybatisplus: 3.4.2
lombok:1.18.12
代碼設(shè)計
代碼涉及四個關(guān)鍵的類:
JoinBuilder
這是一個建造者類,主要適用于生成關(guān)聯(lián)查詢的語句
CaseBuilder
這也是一個建造者類,主要是用來生成連接查詢的條件語句
MyQueryWrapper
這是查詢器,這里繼承了官方的QueryWrapper,然后擴(kuò)展了一些功能。添加了關(guān)聯(lián)查詢的功能
JoinQueryInterceptor
這是SQL攔截器,在上面使用自定義的查詢器添加了關(guān)聯(lián)查詢之后就可以使用SQL攔截器進(jìn)行sql的構(gòu)造
類關(guān)系圖如下:

代碼實現(xiàn)
實現(xiàn)連接條件構(gòu)造器
package com.jenkin.common.config;
import cn.hutool.core.util.ArrayUtil;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;
import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.parser.CCJSqlParserManager;
import net.sf.jsqlparser.statement.select.Join;
import net.sf.jsqlparser.statement.select.PlainSelect;
import net.sf.jsqlparser.statement.select.Select;
import java.io.StringReader;
import java.util.HashSet;
import java.util.Set;
/**
* @author jenkin
* @Since 2021年4月12日14:45:58
* @Version 1.0
* @Description : 關(guān)聯(lián)查詢join構(gòu)造器
*/
@Slf4j
public class JoinBuilder {
private StringBuilder sb = new StringBuilder();
/**
* 關(guān)聯(lián)表里面的查詢字段,比如要查詢關(guān)聯(lián)的用戶表里面的用戶名稱
*/
private String[] selectFields;
/**
* 關(guān)聯(lián)表
*/
private String joinTable;
/**
* 查詢字段去重
*/
Set<String> set = new HashSet<>();
/**
* 主表
*/
private String mainTable;
/**
* 關(guān)聯(lián)類型
*/
private String joinType;
private static final String LEFT_BRACKET = " ( ";
private static final String RIGHT_BRACKET = " ) ";
private static final String AND = " AND ";
private static final String OR = " OR ";
/**
* 左連接
*/
public static final String LEFT = " left ";
/**
* 右連接
*/
public static final String RIGHT = " right ";
/**
* 內(nèi)連接
*/
public static final String INNER = " inner ";
public JoinBuilder selectField(String... fields) {
this.selectFields = fields;
if (!ArrayUtil.isEmpty(this.selectFields)) {
for (int i = 0; i < this.selectFields.length; i++) {
this.selectFields[i] = StringUtils.camelToUnderline(this.selectFields[i]);
set.add(this.selectFields[i].toUpperCase());
}
}
return this;
}
public Set<String> getSelectFields() {
return set;
}
public String getMainTable() {
return mainTable;
}
public String getSubTable() {
return this.joinTable;
}
/**
* @param joinType 關(guān)聯(lián)類型 JoinBuilder.LEFT,JoinBuilder.RIGHT,JoinBuilder.INNER
* @param mainTable 主表
* @param joinTable 關(guān)聯(lián)表
* @return
*/
public JoinBuilder join(String joinType, String mainTable, String joinTable) {
mainTable = StringUtils.camelToUnderline(mainTable);
;
joinTable = StringUtils.camelToUnderline(joinTable);
;
this.joinTable = joinTable;
this.mainTable = mainTable;
this.joinType = joinType;
return this;
}
public static JoinBuilder build() {
return new JoinBuilder();
}
public JoinBuilder and() {
sb.append(AND);
return this;
}
public JoinBuilder or() {
sb.append(OR);
return this;
}
public StringBuilder getSql() {
return sb;
}
public JoinBuilder on(CaseBuilder builder) {
sb.append(LEFT_BRACKET).append(builder.getSql()).append(RIGHT_BRACKET);
return this;
}
public Join getJoin() {
CCJSqlParserManager pm = new CCJSqlParserManager();
String sql = "select * from " + mainTable + " " + joinType + " join " + joinTable + " on " + sb;
try {
net.sf.jsqlparser.statement.Statement parse = pm.parse(new StringReader(sql));
if (parse instanceof Select) {
return ((PlainSelect) ((Select) parse).getSelectBody()).getJoins().get(0);
}
return null;
} catch (JSQLParserException e) {
log.warn(sql);
e.printStackTrace();
}
return null;
}
/**
* @author jenkin
* @Since 2021年4月12日14:45:58
* @Version 1.0
* @Description : 條件構(gòu)造器,局限于關(guān)聯(lián)查詢
*/
public static class CaseBuilder {
/**
* SQL語句
*/
private StringBuilder sb = new StringBuilder();
private static final String LEFT_BRACKET = " ( ";
private static final String RIGHT_BRACKET = " ) ";
private static final String EQ = "=";
private static final String NE = "<>";
private static final String GT = ">";
private static final String LT = "<";
private static final String GT_EQ = ">=";
private static final String LT_EQ = "<=";
private static final String AND = " AND ";
private static final String OR = " OR ";
public static CaseBuilder build() {
return new CaseBuilder();
}
public StringBuilder getSql() {
return sb;
}
/**
* 把條件表達(dá)式用括號包裹起來
*
* @param builder
* @return
*/
public CaseBuilder brackets(CaseBuilder builder) {
sb.append(LEFT_BRACKET).append(builder.sb).append(RIGHT_BRACKET);
return this;
}
public CaseBuilder and() {
sb.append(AND);
return this;
}
public CaseBuilder or() {
sb.append(OR);
return this;
}
/**
* 規(guī)定左側(cè)為主表的列
* ,右側(cè)為從表的列,不可以寫反
* 注意,在使用定值查詢的時候 例如 on a.name = b.name and age = 1
* 這個時候一樣要遵循左邊為主表,右邊為關(guān)聯(lián)表的規(guī)則.
* 例如
* <p>
* 1、 and里面的條件 age字段是存在在主表里面的 那么就寫成 eq("age",1)
* 2、如果age字段是在關(guān)聯(lián)表里面的,那么應(yīng)該寫成 eq(1,"age")
* <p>
* 其他的條件語句例如,ne,gt,lt等等也適用這個邏輯
*
* @param left 左側(cè)列名稱
* @param right 右側(cè)列名稱
* @return
*/
public CaseBuilder eq(Object left, Object right) {
if (left instanceof String) {
left = StringUtils.camelToUnderline((String) left);
}
if (right instanceof String) {
right = StringUtils.camelToUnderline(String.valueOf(right));
}
sb.append(left).append(EQ).append(right);
return this;
}
/**
* 規(guī)定左側(cè)為主表的列
* ,右側(cè)為從表的列,不可以寫反
*
* @param left 左側(cè)列名稱
* @param right 右側(cè)列名稱
* @return
*/
public CaseBuilder ne(String left, Object right) {
left = StringUtils.camelToUnderline(left);
if (right instanceof String) {
right = StringUtils.camelToUnderline(String.valueOf(right));
}
sb.append(left).append(NE).append(right);
return this;
}
/**
* 關(guān)聯(lián)查詢一般是列關(guān)聯(lián),如果條件里面有值等式,要做特殊處理,目前還不支持
*
* @param left
* @param right
* @return
*/
@Deprecated
public CaseBuilder gt(String left, Object right) {
sb.append(left).append(GT).append(right);
return this;
}
/**
* 關(guān)聯(lián)查詢一般是列關(guān)聯(lián),如果條件里面有值等式,要做特殊處理,目前還不支持
*
* @param left
* @param right
* @return
*/
@Deprecated
public CaseBuilder gtEq(String left, Object right) {
sb.append(left).append(GT_EQ).append(right);
return this;
}
/**
* 關(guān)聯(lián)查詢一般是列關(guān)聯(lián),如果條件里面有值等式,要做特殊處理,目前還不支持
*
* @param left
* @param right
* @return
*/
@Deprecated
public CaseBuilder lt(String left, Object right) {
sb.append(left).append(LT).append(right);
return this;
}
/**
* 關(guān)聯(lián)查詢一般是列關(guān)聯(lián),如果條件里面有值等式,要做特殊處理,目前還不支持
*
* @param left
* @param right
* @return
*/
@Deprecated
public CaseBuilder ltEq(String left, Object right) {
sb.append(left).append(LT_EQ).append(right);
return this;
}
}
}
定制化QueryWrapper
在這個定制化的查詢器里面添加了一個addJoin的方法用來添加關(guān)聯(lián)查詢
package com.jenkin.common.config;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import com.jenkin.common.entity.qos.Sort;
import java.util.ArrayList;
import java.util.List;
/**
* @author :jenkin
* @date :Created at 2020/3/13 12:07
* @description:條件構(gòu)造器,重寫字符串轉(zhuǎn)換方法
* @modified By:
* @version: 1.0
*/
public class
MyQueryWrapper<T> extends QueryWrapper<T> {
/**
* 關(guān)聯(lián)查詢構(gòu)造器
*/
private final List<JoinBuilder> joinBuilder = new ArrayList<>();
/**
* 獲取 columnName
*
* @param column
*/
@Override
protected String columnToString(String column) {
return StringUtils.camelToUnderline(column);
}
public static<T> MyQueryWrapper<T> query(){
return new MyQueryWrapper<T>();
}
/**
* 關(guān)聯(lián)查詢構(gòu)造
* @param builder
* @return
*/
public MyQueryWrapper<T> addJoin(JoinBuilder builder){
this.joinBuilder.add(builder);
return this;
}
public List<JoinBuilder> getJoinBuilder() {
return joinBuilder;
}
/**
* 排序
* @param sorts
* @return
*/
public QueryWrapper<T> sort(List<Sort> sorts){
if(!CollectionUtils.isEmpty(sorts)){
sorts.forEach(item->{
orderBy(item.getSortField()!=null,"asc".equals(item.getSortValue()),item.getSortField());
});
}
return this;
}
}
定義SQL攔截器
通過自定義的SQL攔截器去攔截我們寫好的關(guān)聯(lián)查詢,然后生成對應(yīng)的SQL
package com.jenkin.common.config;
import com.alibaba.nacos.client.naming.utils.CollectionUtils;
import com.baomidou.mybatisplus.core.toolkit.PluginUtils;
import com.baomidou.mybatisplus.extension.parser.JsqlParserSupport;
import com.baomidou.mybatisplus.extension.plugins.inner.InnerInterceptor;
import net.sf.jsqlparser.expression.Alias;
import net.sf.jsqlparser.expression.BinaryExpression;
import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.expression.Parenthesis;
import net.sf.jsqlparser.expression.operators.relational.Between;
import net.sf.jsqlparser.expression.operators.relational.IsNullExpression;
import net.sf.jsqlparser.schema.Column;
import net.sf.jsqlparser.schema.Table;
import net.sf.jsqlparser.statement.delete.Delete;
import net.sf.jsqlparser.statement.insert.Insert;
import net.sf.jsqlparser.statement.select.*;
import net.sf.jsqlparser.statement.update.Update;
import org.apache.ibatis.binding.MapperMethod;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* @author jenkin
* @className JoinQueryInterceptor
* @description TODO
* @date 2021/4/12 14:58
*/
public class JoinQueryInterceptor extends JsqlParserSupport implements InnerInterceptor {
/**
* 保存我們的關(guān)聯(lián)查詢的上下文信息
*/
static ThreadLocal<List<JoinBuilder>> joinBuilderThreadLocal = new ThreadLocal<>();
/**
* 操作前置處理
* <p>
* 改改sql啥的
*
* @param executor Executor(可能是代理對象)
* @param ms MappedStatement
* @param parameter parameter
* @param rowBounds rowBounds
* @param resultHandler resultHandler
* @param boundSql boundSql
*/
@Override
public void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds,
ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
if (parameter instanceof MapperMethod.ParamMap) {
for (Object value : ((MapperMethod.ParamMap) parameter).values()) {
if (value instanceof MyQueryWrapper) {
List<JoinBuilder> joinBuilders = ((MyQueryWrapper) value).getJoinBuilder();
if(!CollectionUtils.isEmpty(joinBuilders)){
joinBuilderThreadLocal.set(joinBuilders);
try {
logger.debug("開始添加關(guān)聯(lián)查詢SQL");
String s = this.parserSingle(boundSql.getSql(), parameter);
logger.debug("加了關(guān)聯(lián)查詢的SQL : "+ s);
PluginUtils.MPBoundSql mpBs = PluginUtils.mpBoundSql(boundSql);
mpBs.sql(s);
}finally {
joinBuilderThreadLocal.remove();
}
return;
}
}
}
}
}
/**
* 查詢
*/
@Override
protected void processSelect(Select select, int index, String sql, Object obj) {
List<JoinBuilder> joinBuilders = joinBuilderThreadLocal.get();
PlainSelect selectBody = (PlainSelect) select.getSelectBody();
if (selectBody.getFromItem().getAlias()==null) {
selectBody.getFromItem().setAlias(new Alias("mainjointable"));
}
setJoins(selectBody,joinBuilders);
}
private void setJoins(PlainSelect selectBody,List<JoinBuilder> joinBuilders) {
List<SelectItem> selectItems = selectBody.getSelectItems();
Expression where = selectBody.getWhere();
List<Join> joins = new ArrayList<>();
for (int i = 0; i < joinBuilders.size(); i++) {
JoinBuilder joinBuilder = joinBuilders.get(i);
Join builderJoin = joinBuilder.getJoin();
Set<String> selectFields = new HashSet<>(joinBuilder.getSelectFields());
Join join = new Join();
join.setLeft(builderJoin.isLeft());
join.setRight(builderJoin.isRight());
join.setInner(builderJoin.isInner());
Table table = new Table(joinBuilder.getSubTable());
table.setAlias( new Alias("subjointable"+i));
setSelectItems(table,selectFields,selectItems,selectBody);
join.setRightItem(table);
// Expression expression = getOnExpressionWithTable(joinBuilder);
Expression onExpression = joinBuilder.getJoin().getOnExpression();
selectFields = new HashSet<>(joinBuilder.getSelectFields());
setOnCase(onExpression,table,selectFields,(Table) selectBody.getFromItem(),false);
join.setOnExpression(onExpression);
joins.add(join);
selectFields = new HashSet<>(joinBuilder.getSelectFields());
setWhere(where,table,selectFields,(Table) selectBody.getFromItem());
}
selectBody.setJoins(joins);
}
// private Expression getOnExpressionWithTable(JoinBuilder joinBuilder) {
setWhere(joinBuilder.getJoin().getOnExpression(),);
// return joinBuilder.getJoin().getOnExpression();
// }
private void setSelectItems(Table table, Set<String> selectFields, List<SelectItem> selectItems, PlainSelect selectBody) {
for (SelectItem selectItem : selectItems) {
if (selectItem instanceof SelectExpressionItem) {
if (((SelectExpressionItem) selectItem).getExpression() instanceof Column && selectBody.getFromItem() instanceof Table) {
Column expression = (Column) ((SelectExpressionItem) selectItem).getExpression();
if (expression.getTable()==null&&selectFields.contains(expression.getColumnName().toUpperCase())){
expression.setTable(table);
selectFields.remove(expression.getColumnName().toUpperCase());
}else if(expression.getTable()==null){
expression.setTable((Table) selectBody.getFromItem());
}
}
}
}
if (!selectFields.isEmpty()){
for (String selectField : selectFields) {
SelectExpressionItem selectExpressionItem = new SelectExpressionItem();
Column column = new Column();
column.setTable(table);
column.setColumnName(selectField);
selectExpressionItem.setExpression(column);
selectItems.add(selectExpressionItem);
}
}
}
/**
*
* @param on
* @param subTable
* @param joinSelectFields
* @param sourceTable
* @param isLeft 是否是左側(cè)列,如果是那么就是主表,如果false,那么就是關(guān)聯(lián)表,如果為null,那么就需要根據(jù)join字段判斷
*/
private void setOnCase(Object on, Table subTable, Set<String> joinSelectFields , Table sourceTable,Boolean isLeft) {
if (on==null) {
return;
}
if (on instanceof Column) {
Column column = (Column) on;
if((column).getTable()==null &&isLeft!=null){
(column).setTable(isLeft?sourceTable:subTable);
}
if (isLeft==null&&column.getTable()==null){
(column).setTable(joinSelectFields.contains(column.getColumnName().toUpperCase())?subTable:sourceTable);
}
}else if (on instanceof BinaryExpression){
setOnCase(((BinaryExpression) on).getLeftExpression(),subTable,joinSelectFields,sourceTable,true);
setOnCase(((BinaryExpression) on).getRightExpression(),subTable,joinSelectFields,sourceTable,false);
}else if (on instanceof Parenthesis){
setOnCase(((Parenthesis) on).getExpression(),subTable,joinSelectFields,sourceTable,false);
}else if(on instanceof IsNullExpression){
setOnCase(((IsNullExpression) on).getLeftExpression(),subTable,joinSelectFields,sourceTable,null);
}else if (on instanceof Between){
setOnCase(((Between) on).getLeftExpression(),subTable,joinSelectFields,sourceTable,null);
}
//有其他條件再補(bǔ)充
}
private void setWhere(Object where, Table subTable, Set<String> joinSelectFields , Table sourceTable) {
if (where==null) {
return;
}
if (where instanceof Column) {
Column column = (Column) where;
if((column).getTable()==null&&joinSelectFields.contains((column).getColumnName().toUpperCase())){
(column).setTable(subTable);
}else if((column).getTable()==null){
(column).setTable(sourceTable);
}
}else if (where instanceof BinaryExpression){
setWhere(((BinaryExpression) where).getLeftExpression(),subTable,joinSelectFields,sourceTable);
setWhere(((BinaryExpression) where).getRightExpression(),subTable,joinSelectFields,sourceTable);
}else if (where instanceof Parenthesis){
setWhere(((Parenthesis) where).getExpression(),subTable,joinSelectFields,sourceTable);
}else if(where instanceof IsNullExpression){
setWhere(((IsNullExpression) where).getLeftExpression(),subTable,joinSelectFields,sourceTable);
}else if(where instanceof Between){
setWhere(((Between) where).getLeftExpression(),subTable,joinSelectFields,sourceTable);
}
//有其他條件再補(bǔ)充
}
}
注入攔截器
緊接著只需要在mybatisplus的配置文件里面注入這個攔截器就可以了

使用示例
使用的過程我們分為兩步:
添加字段到主表PO
如圖,紅框中的部分是我們添加的需要從其他表里面關(guān)聯(lián)查詢的字段,注意這些字段需要使用@TableField注解標(biāo)注,并且 select字段和exist字段都要為false,不然會影響新增和修改操作

queryWrapper構(gòu)造關(guān)聯(lián)查詢
把字段添加好之后就可以開始寫關(guān)聯(lián)查詢了,下奶的示例應(yīng)該是一個涵蓋了大部分場景的示例了,多表關(guān)聯(lián),多條件關(guān)聯(lián),等等
MyQueryWrapper<MenuPo> queryWrapper = new MyQueryWrapper<>();
//添加一個關(guān)聯(lián)表查詢,關(guān)聯(lián)用戶表
queryWrapper.addJoin(
JoinBuilder.build()
//查詢用戶表里面的用戶名稱和用戶郵箱字段
.selectField(MenuPo.Fields.userName, MenuPo.Fields.userEmail)
//使用左連接關(guān)聯(lián)
.join(JoinBuilder.LEFT, MenuPo.class, UserPo.class)
//設(shè)置關(guān)聯(lián)條件
.on(JoinBuilder.CaseBuilder.build()
//主表的創(chuàng)建人字段等于關(guān)聯(lián)表的用戶編碼字段
// 注意,在條件中默認(rèn)是第一個參數(shù)為主表的字段,第二個參數(shù)為關(guān)聯(lián)表的字段
.eq(BasePo.Fields.createdBy, UserPo.Fields.userCode)
)
//再添加一個關(guān)聯(lián)查詢,關(guān)聯(lián)角色表
).addJoin(
JoinBuilder.build()
//查血角色表里面的角色名稱
.selectField(MenuPo.Fields.roleName)
//左連接
.join(JoinBuilder.LEFT,MenuPo.class, RolePo.class)
//關(guān)聯(lián)條件
.on(JoinBuilder.CaseBuilder.build()
//code等于角色code
.eq(MenuPo.Fields.code, RolePo.Fields.roleCode)
//并且
.and()
//括號
.brackets(
//parent =-1 or parent =1
JoinBuilder.CaseBuilder.build()
.eq(MenuPo.Fields.parent,-1)
.or()
.eq(MenuPo.Fields.parent,1)
)
)
//外層篩選條件,用戶名=jenkin
).eq(MenuPo.Fields.userName,"jenkin");
//執(zhí)行查詢
menuService.list(queryWrapper);
可以在控制臺看到執(zhí)行的SQL:
SELECT mainjointable.id, mainjointable.NAME, mainjointable.CODE, mainjointable.parent, mainjointable.menu_level, mainjointable.permissions, mainjointable.menu_url, mainjointable.menu_icon, mainjointable.menu_order, mainjointable.menu_type, mainjointable.delete_flag, mainjointable.created_by, mainjointable.creation_date, mainjointable.last_update_date, mainjointable.last_updated_by, mainjointable.version_number, subjointable0.USER_EMAIL, subjointable0.USER_NAME, subjointable1.ROLE_NAME FROM lsc_menu AS mainjointable LEFT JOIN lsc_user AS subjointable0 ON ( mainjointable.created_by = subjointable0.user_code ) LEFT JOIN lsc_role AS subjointable1 ON ( mainjointable.CODE = subjointable1.role_code AND ( mainjointable.parent = - 1 OR mainjointable.parent = 1 ) ) WHERE mainjointable.delete_flag = 0 AND ( subjointable0.user_name = ?)
到此這篇關(guān)于基于mybatisplus 的SQL攔截器實現(xiàn)關(guān)聯(lián)查詢的文章就介紹到這了,更多相關(guān)mybatisplus關(guān)聯(lián)查詢內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家!
- MybatisPlus攔截器如何實現(xiàn)數(shù)據(jù)表分表
- mybatis-plus配置攔截器實現(xiàn)sql完整打印的代碼設(shè)計
- MyBatis-Plus攔截器實現(xiàn)數(shù)據(jù)權(quán)限控制的方法
- Mybatis-plus通過添加攔截器實現(xiàn)簡單數(shù)據(jù)權(quán)限
- MybatisPlusInterceptor實現(xiàn)sql攔截器超詳細(xì)教程
- MyBatis-Plus攔截器實現(xiàn)數(shù)據(jù)權(quán)限控制的示例
- mybatis-plus 攔截器敏感字段加解密的實現(xiàn)
- MyBatis-Plus攔截器對敏感數(shù)據(jù)實現(xiàn)加密
- mybatis-plus攔截器、字段填充器、類型處理器、表名替換、SqlInjector(聯(lián)合主鍵處理)
- Mybatis Plus 3.4.0分頁攔截器的用法小結(jié)
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