关于QueryWrapper,实现MybatisPlus多表关联查询方式
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QueryWrapper实现MybatisPlus多表关联查询
1.dao层接口使用Select注解写SQL
重点：@Param("ew") Wrapper参数是必须，因为${ew.customSqlSegment} 底层其实就是where 条件，所以为了保证Wrapper不为空，service层代码中的Wrapper至少需要有一个条件：1 = 1
@Override
@Select("select a.code as code , b.name as name , b.barcode as barcode , a.ware_code as wareCode , c.name as wareName , a.qty as qty , a.oprice as oprice , a.total as total , " +
" a.id as id , a.create_by as createBy , a.create_date as createDate , a.update_by as updateBy , a.update_date as updateDate , a.status as status , a.remarks as remarks " +
"from sku_stock a , goods b , warehouse c " +
"${ew.customSqlSegment} and a.code = b.code and a.ware_code = c.code")
IPage<SkuStock> selectPage(IPage<SkuStock> page, @Param("ew")Wrapper<SkuStock> queryWrapper);2.service层代码示例
service父类封装的findPage方法：
public IPage<T> findPage(T entity , Map<String , Object> search , String... args){
long current = 1L;
long size = 10L;
if (EmptyUtil.isNoEmpty(ReflexUtil.getFieldValue(entity , "page")) && (long) ReflexUtil.getFieldValue(entity , "page") != 0){
current = (long) ReflexUtil.getFieldValue(entity , "page");
}
if (EmptyUtil.isNoEmpty(ReflexUtil.getFieldValue(entity , "limit")) && (long) ReflexUtil.getFieldValue(entity , "limit") != 0){
size = (long) ReflexUtil.getFieldValue(entity , "limit");
}
QueryWrapper<T> queryWrapper;
if (EmptyUtil.isNoEmpty(search)){
queryWrapper = new QueryWrapper<>();
for (Map.Entry<String , Object> entry:search.entrySet()
) {
String[] key = entry.getKey().split(";");
if (key.length > 1){
if (key[1].equals("eq")){
queryWrapper.eq(key[0] , entry.getValue());
}else if (key[1].equals("ge")){
queryWrapper.ge(key[0] , entry.getValue());
}else if (key[1].equals("lt")){
queryWrapper.lt(key[0] , entry.getValue());
}
}else {
queryWrapper.like(entry.getKey() , entry.getValue());
}
}
}else {
queryWrapper = new QueryWrapper<>(entity);
}
queryWrapper.orderByAsc(args);
return super.page(new Page<T>(current , size) , queryWrapper);
}service实现类方法：
public IPage<SkuStock> findPage(SkuStock entity, String... args) {
Map<String , Object> search = null;
search = new HashedMap();
search.put("1;eq" , "1");
if (EmptyUtil.isNoEmpty(entity.getCode())
|| EmptyUtil.isNoEmpty(entity.getWareCode())
){
if (EmptyUtil.isNoEmpty(entity.getCode())){
search.put("code" , entity.getCode());
}
if (EmptyUtil.isNoEmpty(entity.getWareCode())){
search.put("ware_code" , entity.getWareCode());
}
}else {
long limit = entity.getLimit();
long page = entity.getPage();
entity = new SkuStock();
entity.setLimit(limit);
entity.setPage(page);
}
return super.findPage(entity , search , args);
}3.反射工具类
package org.bluedream.comm.utils;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class ReflexUtil {
public static List<Field> getObjectFields(Object obj){
Class clazz = obj.getClass();
List<Field> fieldList = new ArrayList<>() ;
while (clazz != null) {//当父类为null的时候说明到达了最上层的父类(Object类).
fieldList.addAll(Arrays.asList(clazz .getDeclaredFields()));
clazz = clazz.getSuperclass(); //得到父类,然后赋给自己
}
return fieldList;
}
public static List<Field> getObjectFields(Class<?> clazz){
List<Field> fieldList = new ArrayList<>() ;
while (clazz != null){
fieldList.addAll(Arrays.asList(clazz .getDeclaredFields()));
clazz = clazz.getSuperclass(); //得到父类,然后赋给自己
}
return fieldList;
}
public static Boolean isField(String fieldName , Object entity){
List<Field> fieldList = getObjectFields(entity);
for (Field f1:fieldList
) {
if (fieldName.equals(f1.getName()))
return true;
}
return false;
}
public static List<Method> getObjectMethods(Object entity){
Class<?> clazz = entity.getClass();
List<Method> methods = new ArrayList<>();
while (clazz != null && clazz != Object.class) {//当父类为null的时候说明到达了最上层的父类(Object类).
methods.addAll(Arrays.asList(clazz .getDeclaredMethods()));
clazz = clazz.getSuperclass(); //得到父类,然后赋给自己
}
return methods;
}
public static List<Method> getObjectMethods(Class<?> clazz){
List<Method> methods = new ArrayList<>();
while (clazz != null && clazz != Object.class) {//当父类为null的时候说明到达了最上层的父类(Object类).
methods.addAll(Arrays.asList(clazz .getDeclaredMethods()));
clazz = clazz.getSuperclass(); //得到父类,然后赋给自己
}
return methods;
}
public static Boolean isMethod(String methodName , Object entity){
List<Method> methods = getObjectMethods(entity);
for (Method m1:methods
) {
if (methodName.equals(m1.getName()))
return true;
}
return false;
}
public static Method getDeclaredMethod(Object obj , String methodName , Class<?>...parameterTypes) {
for (Class<?> clazz = obj.getClass(); clazz != Object.class && clazz != null; clazz = clazz.getSuperclass()) {
try {
return clazz.getDeclaredMethod(methodName, parameterTypes);
} catch (Exception e) {
// 这里甚么都不要做！并且这里的异常必须这样写，不能抛出去。
// 如果这里的异常打印或者往外抛，则就不会执行clazz=clazz.getSuperclass(),最后就不会进入到父类中了
}
}
return null;
}
public static Object invoke(Object object, String methodName, Class<?>[] parameterTypes,
Object[] parameters){
Method method = getDeclaredMethod(object, methodName, parameterTypes);
try {
if (method != null){
method.setAccessible(true);
// 调用object 的 method 所代表的方法，其方法的参数是 parameters
return method.invoke(object, parameters);
}
}catch (Exception e1){
e1.printStackTrace();
}
return null;
}
public static Field getDeclaredField(Object object, String fieldName) {
Field field = null;
Class<?> clazz = object.getClass();
for (; clazz != Object.class && clazz != null; clazz = clazz.getSuperclass()) {
try {
field = clazz.getDeclaredField(fieldName);
return field;
} catch (Exception e) {
// 这里甚么都不要做！并且这里的异常必须这样写，不能抛出去。
// 如果这里的异常打印或者往外抛，则就不会执行clazz = clazz.getSuperclass(),最后就不会进入到父类中了
}
}
return null;
}
public static void setFieldValue(Object object, String fieldName, Object value) {
// 根据 对象和属性名通过反射 调用上面的方法获取 Field对象
Field field = getDeclaredField(object, fieldName);
if (field != null){
// 抑制Java对其的检查
field.setAccessible(true);
try {
// 将 object 中 field 所代表的值 设置为 value
field.set(object, value);
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
public static Object getFieldValue(Object object, String fieldName) {
// 根据 对象和属性名通过反射 调用上面的方法获取 Field对象
Field field = getDeclaredField(object, fieldName);
if (field != null){
// 抑制Java对其的检查
field.setAccessible(true);
try {
// 获取 object 中 field 所代表的属性值
return field.get(object);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
}4.判空工具类
package org.bluedream.comm.utils;
import java.util.Collection;
import java.util.Map;
public class EmptyUtil {
//Suppress default constructor for noninstantiability
private EmptyUtil(){
throw new AssertionError();
}
public static boolean isEmpty(Object object){
if (object == null){
return true;
}
if (object instanceof int[]){
return ((int[]) object).length == 0;
}
if (object instanceof double[]){
return ((double[]) object).length == 0;
}
if (object instanceof long[]){
return ((long[]) object).length == 0;
}
if (object instanceof byte[]){
return ((byte[]) object).length == 0;
}
if (object instanceof short[]){
return ((short[]) object).length == 0;
}
if (object instanceof float[]){
return ((float[]) object).length == 0;
}
if (object instanceof char[]){
return ((char[]) object).length == 0;
}
if (object instanceof Object[]){
return ((Object[]) object).length == 0;
}
if (object instanceof CharSequence) {
return ((CharSequence) object).length() == 0;
}
if (object instanceof Collection ){
return ((Collection) object).isEmpty();
}
if (object instanceof Map){
return ((Map) object).isEmpty();
}
return false;
}
public static boolean isNoEmpty(Object object){
return !isEmpty(object);
}
}MybatisPlus QueryWrapper简单用法
查询方式 | 说明 |
setSqlSelect | 设置 SELECT 查询字段 |
where | WHERE 语句，拼接 +?WHERE 条件 |
and | AND 语句，拼接 +?AND 字段=值 |
andNew | AND 语句，拼接 +?AND (字段=值) |
or | OR 语句，拼接 +?OR 字段=值 |
orNew | OR 语句，拼接 +?OR (字段=值) |
eq | 等于= |
allEq | 基于 map 内容等于= |
ne | 不等于<> |
gt | 大于> |
ge | 大于等于>= |
lt | 小于< |
le | 小于等于<= |
like | 模糊查询 LIKE |
notLike | 模糊查询 NOT LIKE |
in | IN 查询 |
notIn | NOT IN 查询 |
isNull | NULL 值查询 |
isNotNull | IS NOT NULL |
groupBy | 分组 GROUP BY |
having | HAVING 关键词 |
orderBy | 排序 ORDER BY |
orderAsc | ASC 排序 ORDER BY |
orderDesc | DESC 排序 ORDER BY |
exists | EXISTS 条件语句 |
notExists | NOT EXISTS 条件语句 |
between | BETWEEN 条件语句 |
notBetween | NOT BETWEEN 条件语句 |
addFilter | 自由拼接 SQL |
last | 拼接在最后，例如：last(“LIMIT 1”) |
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
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