MyBaties 动态SQL话语

2013-01-26

MyBaties 动态SQL语句!-- 插入学生自动主键--insert idcreateStudentAutoKey parameterTypelimin

MyBaties 动态SQL语句
<insert id="createStudentAutoKey" parameterType="liming.student.manager.data.model.StudentEntity" keyProperty="studentId"><selectKey keyProperty="studentId" resultType="String" order="BEFORE">select nextval('student')</selectKey>INSERT INTO STUDENT_TBL(STUDENT_ID, STUDENT_NAME, STUDENT_SEX, STUDENT_BIRTHDAY, STUDENT_PHOTO, CLASS_ID, PLACE_ID)VALUES (#{studentId},#{studentName},#{studentSex},#{studentBirthday}, #{studentPhoto, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler}, #{classId}, #{placeId})</insert>

?调用接口方法，和获取自动生成key

StudentEntity entity = new StudentEntity();entity.setStudentName("黎明你好");entity.setStudentSex(1);entity.setStudentBirthday(DateUtil.parse("1985-05-28"));entity.setClassId("20000001");entity.setPlaceId("70000001");this.dynamicSqlMapper.createStudentAutoKey(entity);System.out.println("新增学生ID: " + entity.getStudentId());

?selectKey语句属性配置细节：

属性描述取值keyPropertyselectKey?语句生成结果需要设置的属性。?resultType生成结果类型，MyBatis?允许使用基本的数据类型，包括String?、int类型。?order

<select id="getStudentListLikeName" parameterType="StudentEntity" resultMap="studentResultMap">SELECT * from STUDENT_TBL ST WHERE ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName}),'%')</select>

?是此时如果studentName或studentSex为null，此语句很可能报错或查询结果为空。此时我们使用if动态sql语句先进行判断，如果值为null或等于空字符串，我们就不进行此条件的判断，增加灵活性。

参数为实体类StudentEntity。将实体类中所有的属性均进行判断，如果不为空则执行判断条件。

<!-- 2 if(判断参数) - 将实体类不为空的属性作为where条件 --><select id="getStudentList_if" resultMap="resultMap_studentEntity" parameterType="liming.student.manager.data.model.StudentEntity">SELECT ST.STUDENT_ID,   ST.STUDENT_NAME,   ST.STUDENT_SEX,   ST.STUDENT_BIRTHDAY,   ST.STUDENT_PHOTO,   ST.CLASS_ID,   ST.PLACE_ID  FROM STUDENT_TBL ST  WHERE<if test="studentName !=null ">ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName, jdbcType=VARCHAR}),'%')</if><if test="studentSex != null and studentSex != '' ">AND ST.STUDENT_SEX = #{studentSex, jdbcType=INTEGER}</if><if test="studentBirthday != null ">AND ST.STUDENT_BIRTHDAY = #{studentBirthday, jdbcType=DATE}</if><if test="classId != null and classId!= '' ">AND ST.CLASS_ID = #{classId, jdbcType=VARCHAR}</if><if test="classEntity != null and classEntity.classId !=null and classEntity.classId !=' ' ">AND ST.CLASS_ID = #{classEntity.classId, jdbcType=VARCHAR}</if><if test="placeId != null and placeId != '' ">AND ST.PLACE_ID = #{placeId, jdbcType=VARCHAR}</if><if test="placeEntity != null and placeEntity.placeId != null and placeEntity.placeId != '' ">AND ST.PLACE_ID = #{placeEntity.placeId, jdbcType=VARCHAR}</if><if test="studentId != null and studentId != '' ">AND ST.STUDENT_ID = #{studentId, jdbcType=VARCHAR}</if></select>

?使用时比较灵活，?new一个这样的实体类，我们需要限制那个条件，只需要附上相应的值就会where这个条件，相反不去赋值就可以不在where中判断。

public void select_test_2_1() {StudentEntity entity = new StudentEntity();entity.setStudentName("");entity.setStudentSex(1);entity.setStudentBirthday(DateUtil.parse("1985-05-28"));entity.setClassId("20000001");//entity.setPlaceId("70000001");List<StudentEntity> list = this.dynamicSqlMapper.getStudentList_if(entity);for (StudentEntity e : list) {System.out.println(e.toString());}}

3.3 if + where?的条件判断

@Testpublic void select_test_2_1() {StudentEntity entity = new StudentEntity();entity.setStudentName(null);entity.setStudentSex(1);List<StudentEntity> list = this.dynamicSqlMapper.getStudentList_if(entity);for (StudentEntity e : list) {System.out.println(e.toString());}}

?如果上面例子，参数studentName为null，将不会进行STUDENT_NAME列的判断，则会直接导“WHERE AND”关键字多余的错误SQL。

<select id="getStudentList_whereIf" resultMap="resultMap_studentEntity" parameterType="liming.student.manager.data.model.StudentEntity">SELECT ST.STUDENT_ID, ST.STUDENT_NAME, ST.STUDENT_SEX, ST.STUDENT_BIRTHDAY, ST.STUDENT_PHOTO, ST.CLASS_ID, ST.PLACE_ID FROM STUDENT_TBL ST <where><if test="studentName !=null ">ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName, jdbcType=VARCHAR}),'%')</if><if test="studentSex != null and studentSex != '' ">AND ST.STUDENT_SEX = #{studentSex, jdbcType=INTEGER}</if><if test="studentBirthday != null ">AND ST.STUDENT_BIRTHDAY = #{studentBirthday, jdbcType=DATE}</if><if test="classId != null and classId!= '' ">AND ST.CLASS_ID = #{classId, jdbcType=VARCHAR}</if><if test="classEntity != null and classEntity.classId !=null and classEntity.classId !=' ' ">AND ST.CLASS_ID = #{classEntity.classId, jdbcType=VARCHAR}</if><if test="placeId != null and placeId != '' ">AND ST.PLACE_ID = #{placeId, jdbcType=VARCHAR}</if><if test="placeEntity != null and placeEntity.placeId != null and placeEntity.placeId != '' ">AND ST.PLACE_ID = #{placeEntity.placeId, jdbcType=VARCHAR}</if><if test="studentId != null and studentId != '' ">AND ST.STUDENT_ID = #{studentId, jdbcType=VARCHAR}</if></where></select>

3.4 if + set?的更新语句

<update id="updateStudent_if_set" parameterType="liming.student.manager.data.model.StudentEntity">UPDATE STUDENT_TBL<set><if test="studentName != null and studentName != '' ">STUDENT_TBL.STUDENT_NAME = #{studentName},</if><if test="studentSex != null and studentSex != '' ">STUDENT_TBL.STUDENT_SEX = #{studentSex},</if><if test="studentBirthday != null ">STUDENT_TBL.STUDENT_BIRTHDAY = #{studentBirthday},</if><if test="studentPhoto != null ">STUDENT_TBL.STUDENT_PHOTO = #{studentPhoto, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler},</if><if test="classId != '' ">STUDENT_TBL.CLASS_ID = #{classId}</if><if test="placeId != '' ">STUDENT_TBL.PLACE_ID = #{placeId}</if></set>WHERE STUDENT_TBL.STUDENT_ID = #{studentId};</update>

3.5 if + trim代替where/set标签

<select id="getStudentList_if_trim" resultMap="resultMap_studentEntity">SELECT ST.STUDENT_ID, ST.STUDENT_NAME, ST.STUDENT_SEX, ST.STUDENT_BIRTHDAY, ST.STUDENT_PHOTO, ST.CLASS_ID, ST.PLACE_ID FROM STUDENT_TBL ST <trim prefix="WHERE" prefixOverrides="AND|OR"><if test="studentName !=null ">ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName, jdbcType=VARCHAR}),'%')</if><if test="studentSex != null and studentSex != '' ">AND ST.STUDENT_SEX = #{studentSex, jdbcType=INTEGER}</if><if test="studentBirthday != null ">AND ST.STUDENT_BIRTHDAY = #{studentBirthday, jdbcType=DATE}</if><if test="classId != null and classId!= '' ">AND ST.CLASS_ID = #{classId, jdbcType=VARCHAR}</if><if test="classEntity != null and classEntity.classId !=null and classEntity.classId !=' ' ">AND ST.CLASS_ID = #{classEntity.classId, jdbcType=VARCHAR}</if><if test="placeId != null and placeId != '' ">AND ST.PLACE_ID = #{placeId, jdbcType=VARCHAR}</if><if test="placeEntity != null and placeEntity.placeId != null and placeEntity.placeId != '' ">AND ST.PLACE_ID = #{placeEntity.placeId, jdbcType=VARCHAR}</if><if test="studentId != null and studentId != '' ">AND ST.STUDENT_ID = #{studentId, jdbcType=VARCHAR}</if></trim></select>

3.5.2 trim代替set

<!-- 5.2 if/trim代替set(判断参数) - 将实体类不为空的属性更新 --><update id="updateStudent_if_trim" parameterType="liming.student.manager.data.model.StudentEntity">UPDATE STUDENT_TBL<trim prefix="SET" suffixOverrides=","><if test="studentName != null and studentName != '' ">STUDENT_TBL.STUDENT_NAME = #{studentName},</if><if test="studentSex != null and studentSex != '' ">STUDENT_TBL.STUDENT_SEX = #{studentSex},</if><if test="studentBirthday != null ">STUDENT_TBL.STUDENT_BIRTHDAY = #{studentBirthday},</if><if test="studentPhoto != null ">STUDENT_TBL.STUDENT_PHOTO = #{studentPhoto, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler},</if><if test="classId != '' ">STUDENT_TBL.CLASS_ID = #{classId},</if><if test="placeId != '' ">STUDENT_TBL.PLACE_ID = #{placeId}</if></trim>WHERE STUDENT_TBL.STUDENT_ID = #{studentId}</update>

3.6 choose (when, otherwise)

? ? 有时候我们并不想应用所有的条件，而只是想从多个选项中选择一个。而使用if标签时，只要test中的表达式为true，就会执行if标签中的条件。MyBatis提供了choose 元素。if标签是与(and)的关系，而choose比傲天是或（or）的关系。

? ? choose标签是按顺序判断其内部when标签中的test条件出否成立，如果有一个成立，则choose结束。当choose中所有when的条件都不满则时，则执行otherwise中的sql。类似于Java 的switch 语句，choose为switch，when为case，otherwise则为default。

? ? 例如下面例子，同样把所有可以限制的条件都写上，方面使用。choose会从上到下选择一个when标签的test为true的sql执行。安全考虑，我们使用where将choose包起来，放置关键字多于错误。

<!-- 6 choose(判断参数) - 按顺序将实体类第一个不为空的属性作为where条件 --><select id="getStudentList_choose" resultMap="resultMap_studentEntity" parameterType="liming.student.manager.data.model.StudentEntity">SELECT ST.STUDENT_ID,   ST.STUDENT_NAME,   ST.STUDENT_SEX,   ST.STUDENT_BIRTHDAY,   ST.STUDENT_PHOTO,   ST.CLASS_ID,   ST.PLACE_ID  FROM STUDENT_TBL ST <where><choose><when test="studentName !=null ">ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName, jdbcType=VARCHAR}),'%')</when ><when test="studentSex != null and studentSex != '' ">AND ST.STUDENT_SEX = #{studentSex, jdbcType=INTEGER}</when ><when test="studentBirthday != null ">AND ST.STUDENT_BIRTHDAY = #{studentBirthday, jdbcType=DATE}</when ><when test="classId != null and classId!= '' ">AND ST.CLASS_ID = #{classId, jdbcType=VARCHAR}</when ><when test="classEntity != null and classEntity.classId !=null and classEntity.classId !=' ' ">AND ST.CLASS_ID = #{classEntity.classId, jdbcType=VARCHAR}</when ><when test="placeId != null and placeId != '' ">AND ST.PLACE_ID = #{placeId, jdbcType=VARCHAR}</when ><when test="placeEntity != null and placeEntity.placeId != null and placeEntity.placeId != '' ">AND ST.PLACE_ID = #{placeEntity.placeId, jdbcType=VARCHAR}</when ><when test="studentId != null and studentId != '' ">AND ST.STUDENT_ID = #{studentId, jdbcType=VARCHAR}</when ><otherwise></otherwise></choose></where></select>

3.7 foreach

public List<StudentEntity> getStudentListByClassIds_foreach_array(String[] classIds);

?动态SQL语句：

<!— 7.1 foreach(循环array参数) - 作为where中in的条件 --><select id="getStudentListByClassIds_foreach_array" resultMap="resultMap_studentEntity">SELECT ST.STUDENT_ID, ST.STUDENT_NAME, ST.STUDENT_SEX, ST.STUDENT_BIRTHDAY, ST.STUDENT_PHOTO, ST.CLASS_ID, ST.PLACE_ID FROM STUDENT_TBL ST WHERE ST.CLASS_ID IN <foreach collection="array" item="classIds" open="(" separator="," close=")"> #{classIds} </foreach></select>

?测试代码，查询学生中，在20000001、20000002这两个班级的学生：

@Testpublic void test7_foreach() {String[] classIds = { "20000001", "20000002" };List<StudentEntity> list = this.dynamicSqlMapper.getStudentListByClassIds_foreach_array(classIds);for (StudentEntity e : list) {System.out.println(e.toString());}}

3.7.2参数为list示例的写法
public List<StudentEntity> getStudentListByClassIds_foreach_list(List<String> classIdList);
<select id="getStudentListByClassIds_foreach_list" resultMap="resultMap_studentEntity">SELECT ST.STUDENT_ID, ST.STUDENT_NAME, ST.STUDENT_SEX, ST.STUDENT_BIRTHDAY, ST.STUDENT_PHOTO, ST.CLASS_ID, ST.PLACE_ID FROM STUDENT_TBL ST WHERE ST.CLASS_ID IN <foreach collection="list" item="classIdList" open="(" separator="," close=")"> #{classIdList} </foreach></select>
@Testpublic void test7_2_foreach() {ArrayList<String> classIdList = new ArrayList<String>();classIdList.add("20000001");classIdList.add("20000002");List<StudentEntity> list = this.dynamicSqlMapper.getStudentListByClassIds_foreach_list(classIdList);for (StudentEntity e : list) {System.out.println(e.toString());}}
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MyBaties 动态SQL话语