當(dāng)數(shù)據(jù)庫字段和實(shí)體bean中屬性不一致時(shí)
之前數(shù)據(jù)庫Person名字字段是name,PersonBean中屬性也是name,但是之后數(shù)據(jù)庫中修改為了user_name,
方法1:通過sql語句的字段起別名,別名和實(shí)體中的對(duì)象屬性一致
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SELECT id,user_name as name,sex,age from person<select id="find" resultType="com.luogg.domain.Person"> SELECT id,user_name as name,sex,age from person</select> |
方法2: mybatis最強(qiáng)大的地方 : reslutMap對(duì)象
添加一個(gè)中介reslutMap標(biāo)簽,并將select標(biāo)簽中的resultType改為resultMap,并對(duì)應(yīng)resultMap標(biāo)簽的id.
結(jié)果集:resultType 基礎(chǔ)類型,int,string,Person,
resultMap 針對(duì)中介標(biāo)簽resultMap而存在.
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<!--配置命名空間,命名空間+ .id 是唯一的sql語句標(biāo)示符--><mapper namespace="com.luogg.mapper.PersonMapper"> <!--中介,當(dāng)數(shù)據(jù)庫字段和實(shí)體bean對(duì)象屬性不一致時(shí),做一個(gè)對(duì)應(yīng)關(guān)系--> <resultMap id="personRM" type="com.luogg.domain.Person"> <!--主鍵映射--> <id property="id" column="ID"></id> <!--普通字段,property指實(shí)體屬性,column結(jié)果集的字段名稱,一致的字段可以不寫--> <result property="name" column="USER_NAME"></result> </resultMap> <!--查詢所有數(shù)據(jù),參數(shù)有id,resultType結(jié)果集,parameterType參數(shù)--> <!--注意 : sql語句中如果有要填寫集合的,比如查詢所有數(shù)據(jù),返回一個(gè)Person的結(jié)果集,那么resultType參數(shù)直接寫 路徑+集合的類型 比如: 返回一個(gè)Person集合,那么就填寫Person Bean所在的路徑+Person--> <select id="find" resultMap="personRM"> SELECT * from person </select> <!--通過ID查詢數(shù)據(jù),當(dāng)有查詢條件時(shí),需要寫parameterType,返回結(jié)果集仍然是Person, #{id}或者${id}都可以--> <select id="selById" parameterType="int" resultType="com.luogg.domain.Person"> SELECT * FROM person WHERE id = #{id} </select></mapper> |
mybatis的增刪改查
新增人員信息
首先在PersonMapper.xml中添加insert標(biāo)簽,我們的數(shù)據(jù)庫字段user_name,Person實(shí)體屬性為name,不一致,區(qū)別開來.然后在TestMybatis中寫入代碼.
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<!--添加人員--> <insert id="insert" parameterType="com.luogg.domain.Person"> INSERT INTO person(id,user_name,age,sex) VALUES(#{id},#{name},#{age},#{sex}) </insert> |
package test;
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import com.luogg.domain.Person;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import java.io.IOException;import java.io.InputStream;import java.util.List;/** * Created by luogg on 2017/2/17. */public class TestMybatis { //SqlSessionFactory為線程安全的 private SqlSessionFactory factory; @Before public void init() throws IOException { String resource = "sqlMapConfig.xml"; InputStream is = Resources.getResourceAsStream(resource); factory = new SqlSessionFactoryBuilder().build(is); } @Test //查詢所有 public void findAll() throws IOException { /** * 測(cè)試數(shù)據(jù)庫的連接 * 1.定義一個(gè)String類型的變量resource,指向剛才配置的連接數(shù)據(jù)庫的xml文件 * 2.創(chuàng)建一個(gè)輸入流,來讀取我們的數(shù)據(jù)庫配置文件 * 3.輸入流創(chuàng)建工廠. * 4.有了工廠之后open工廠 * 5.通過session訪問配置文件中的sql語句 */ SqlSession session = factory.openSession(); //如何訪問PersonMapper.xml中的sql語句呢? 命名空間+ .id List<Person> list = session.selectList("com.luogg.mapper.PersonMapper.find"); System.out.println(list.size()); for(Person p : list){ System.out.println(p); } } @Test //通過ID查詢?nèi)藛T信息 public void selById(){ SqlSession session = factory.openSession(); Person p = session.selectOne("com.luogg.mapper.PersonMapper.selById",1); System.out.println(p); } @Test //添加人員信息 public void add(){ SqlSession session = factory.openSession(); Person p = new Person(); p.setId(4); p.setName("luogg"); p.setAge(22); p.setSex(1); int i = session.insert("com.luogg.mapper.PersonMapper.insert",p); session.commit(); if(i==1){ System.out.print("添加人員成功"); } }} |
修改人員信息 , 查詢總的記錄條數(shù)
prsonMapper.xml文件
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<!--修改成員信息--> <update id="update" parameterType="com.luogg.domain.Person"> UPDATE person SET user_name=#{name},age=#{age} WHERE id=#{id} </update> <!--查詢總的記錄--> <select id="count" resultType="int"> SELECT COUNT(*) FROM person </select> |
TestMybatis.java文件
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@Test //修改人員信息 public void updatePer(){ SqlSession session = factory.openSession(); Person p = new Person(); p.setId(4); p.setName("luoggg"); //p.setSex(1); p.setAge(23); int i = session.update("com.luogg.mapper.PersonMapper.update",p); session.commit(); if(i==1){ System.out.print("修改信息成功"); } } @Test //查詢總的記錄條數(shù) public void selCount(){ SqlSession session = factory.openSession(); int i = session.selectOne("com.luogg.mapper.PersonMapper.count"); System.out.println(i); } |
條件查詢
根據(jù)條件查詢
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<!--帶條件查詢--> <select id="selByL" parameterType="map" resultMap="personRM"> SELECT <include refid="cols"/> FROM person where user_name like #{name} AND sex=#{sex} </select>@Test //帶條 件查詢 public void selByL(){ SqlSession session = factory.openSession(); Map<String,Object> map = new HashMap<String, Object>(); map.put("name","luo%"); map.put("sex",1); List<Person> list = session.selectList("com.luogg.mapper.PersonMapper.selByL",map); System.out.println(list.size()); for(Person p : list){ System.out.println(p); } } |
以上所述是小編給大家介紹的MyBatis入門之增刪改查+數(shù)據(jù)庫字段和實(shí)體字段不一致問題處理方法，希望對(duì)大家有所幫助，如果大家有任何疑問歡迎給我留言，小編會(huì)及時(shí)回復(fù)大家的！
原文鏈接：http://www.cnblogs.com/luogg/archive/2017/05/06/6815882.html
