SpringBoot动态查询 Specification使用

   有时候需要用到动态查询。动态查询 Specification  使用需实现接口JpaSpecificationExecutor

package com.hik.dao;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;

import com.hik.entity.Book;

/**
 * 图书Dao接口
 * @author jed
 *
 */
public interface BookDao extends JpaRepository<Book, Integer>,JpaSpecificationExecutor<Book> {
    
    //Hql语句查询
    @Query("select b from Book b where b.bookName like %?1%")
    public List<Book> findByBookName(String bookName);
    
    //本地sql语句查询
    @Query(value="select * from t_book order by RAND() limit ?1",nativeQuery=true)
    public List<Book> randomList(Integer n);
}

JpaSpecificationExecutor接口方法

/*
 * Copyright 2008-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.jpa.repository;

import java.util.List;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;

/**
 * Interface to allow execution of {@link Specification}s based on the JPA criteria API.
 * 
 * @author Oliver Gierke
 */
public interface JpaSpecificationExecutor<T> {

    /**
     * Returns a single entity matching the given {@link Specification}.
     * 
     * @param spec
     * @return
     */
    T findOne(Specification<T> spec);

    /**
     * Returns all entities matching the given {@link Specification}.
     * 
     * @param spec
     * @return
     */
    List<T> findAll(Specification<T> spec);

    /**
     * Returns a {@link Page} of entities matching the given {@link Specification}.
     * 
     * @param spec
     * @param pageable
     * @return
     */
    Page<T> findAll(Specification<T> spec, Pageable pageable);

    /**
     * Returns all entities matching the given {@link Specification} and {@link Sort}.
     * 
     * @param spec
     * @param sort
     * @return
     */
    List<T> findAll(Specification<T> spec, Sort sort);

    /**
     * Returns the number of instances that the given {@link Specification} will return.
     * 
     * @param spec the {@link Specification} to count instances for
     * @return the number of instances
     */
    long count(Specification<T> spec);
}

Specification接口

/*
 * Copyright 2008-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.jpa.domain;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

/**
 * Specification in the sense of Domain Driven Design.
 * 
 * @author Oliver Gierke
 * @author Thomas Darimont
 * @author Krzysztof Rzymkowski
 */
public interface Specification<T> {

    /**
     * Creates a WHERE clause for a query of the referenced entity in form of a {@link Predicate} for the given
     * {@link Root} and {@link CriteriaQuery}.
     * 
     * @param root
     * @param query
     * @return a {@link Predicate}, may be {@literal null}.
     */
    Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);
}

BookDao接口类：

package com.hik.dao;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;

import com.hik.entity.Book;

/**
 * 图书Dao接口
 * @author jed
 *
 */
public interface BookDao extends JpaRepository<Book, Integer>,JpaSpecificationExecutor<Book> {
    
    //Hql语句查询
    @Query("select b from Book b where b.bookName like %?1%")
    public List<Book> findByBookName(String bookName);
    
    //本地sql语句查询
    @Query(value="select * from t_book order by RAND() limit ?1",nativeQuery=true)
    public List<Book> randomList(Integer n);
}

BookController类

package com.hik.Controller;

import java.util.List;

import javax.annotation.Resource;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import com.hik.dao.BookDao;
import com.hik.entity.Book;

/**
 * Book控制类
 * @author jed
 *
 */
@Controller
@RequestMapping("/book")
public class BookController {
    
    @Resource
    private BookDao bookDao;
    
    /**
     * 查询所有图书
     * @return
     */
    @RequestMapping(value="/list")
    public ModelAndView list() {
        ModelAndView mav = new ModelAndView ();
        mav.addObject("bookList", bookDao.findAll());
        mav.setViewName("bookList");
        return mav;
    }
    
    /**
     * 根据条件动态查询
     * @param book
     * @return
     */
    @RequestMapping(value="/list2")
    public ModelAndView list2(Book book) {
        ModelAndView mav = new ModelAndView();
        List<Book> bookList = bookDao.findAll(new Specification<Book>() {

            @Override
            public Predicate toPredicate(Root<Book> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Predicate predicate= cb.conjunction();
                if(book!=null) {
                    if(book.getBookName()!=null && !"".equals(book.getBookName())) {
                        predicate.getExpressions().add(cb.like(root.get("bookName"), "%"+book.getBookName()+"%"));
                    }
                }
                return predicate;
            }
            
        });
        mav.addObject("bookList",bookList);
        mav.setViewName("bookList");
        return mav;
    }

    /**
     * 添加图书
     * @param book
     * @return
     */
    @RequestMapping(value="/add", method=RequestMethod.POST)
    public String add(Book book) {
        bookDao.save(book);
        return "forward:/book/list";
    }
    
    @GetMapping(value="/preUpdate/{id}")
    public ModelAndView preUpdate(@PathVariable("id") Integer id) {
        ModelAndView mav = new ModelAndView();
        mav.addObject("book", bookDao.getOne(id));
        mav.setViewName("bookUpdate");
        return mav;
    }
    
    /**
     * 修改图书
     * @param book
     * @return
     */
    @PostMapping(value="/update")
    public String update(Book book) {
        bookDao.save(book);
        return "forward:/book/list";
    }
    
    /**
     * 删除图书
     * @param id
     * @return
     */
    @RequestMapping(value="/delete",method = RequestMethod.GET)
    public String delete(Integer id) {
        bookDao.delete(id);
        return "forward:/book/list";
    }
    
    @ResponseBody
    @GetMapping(value="/queryByName")
    public List<Book> queryByName() {
        return bookDao.findByBookName("思想");
    }
    
    @ResponseBody
    @GetMapping(value="/randomList")
    public List<Book> randomList(){
        return bookDao.randomList(2);
    }
}

bookList.ftl

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>图书管理页面</title>
</head>
<body>
<a href="/bookAdd.html">添加图书</a></br>
<form method="post" action="/book/list2">
    图书名称：<input type="text" name="bookName" />&nbsp;
    <input type="submit" value="搜索"/>
</form>
    <table>
        <tr>
            <th>编号</th>
            <th>图书名称</th>
            <th>操作</th>
        </tr>
        <#list bookList as book>     
        <tr>     
            <td>${book.id}</td>     
            <td>${book.bookName}</td>  
            <td>
                <a href="/book/preUpdate/${book.id}">修改</a>
                <a href="/book/delete?id=${book.id}">删除</a>
            </td>
        </tr>  
       </#list>  
    </table>  
</body>
</html>

访问：http://localhost:8888/book/list2

输入查询条件，点击搜索

查询结果：