MyBatis的动态SQL

	<select id="dynamicIfTest" parameterType="Blog" resultType="Blog">
		select * from t_blog where 1 = 1
		<if test="title != null">
			and title = #{title}
		</if>
		<if test="content != null">
			and content = #{content}
		</if>
		<if test="owner != null">
			and owner = #{owner}
		</if>
	</select>

	<select id="dynamicChooseTest" parameterType="Blog" resultType="Blog">
		select * from t_blog where 1 = 1 
		<choose>
			<when test="title != null">
				and title = #{title}
			</when>
			<when test="content != null">
				and content = #{content}
			</when>
			<otherwise>
				and owner = "owner1"
			</otherwise>
		</choose>
	</select>

	<select id="dynamicWhereTest" parameterType="Blog" resultType="Blog">
		select * from t_blog 
		<where>
			<if test="title != null">
				title = #{title}
			</if>
			<if test="content != null">
				and content = #{content}
			</if>
			<if test="owner != null">
				and owner = #{owner}
			</if>
		</where>
	</select>

	<select id="dynamicTrimTest" parameterType="Blog" resultType="Blog">
		select * from t_blog 
		<trim prefix="where" prefixOverrides="and |or">
			<if test="title != null">
				title = #{title}
			</if>
			<if test="content != null">
				and content = #{content}
			</if>
			<if test="owner != null">
				or owner = #{owner}
			</if>
		</trim>
	</select>

	<update id="dynamicSetTest" parameterType="Blog">
		update t_blog
		<set>
			<if test="title != null">
				title = #{title},
			</if>
			<if test="content != null">
				content = #{content},
			</if>
			<if test="owner != null">
				owner = #{owner}
			</if>
		</set>
		where id = #{id}
	</update>

1. 如果传入的是单参数且参数类型是一个List的时候，collection属性值为list
2. 如果传入的是单参数且参数类型是一个array数组的时候，collection的属性值为array
3. 如果传入的参数是多个的时候，我们就需要把它们封装成一个Map了，当然单参数也可以封装成map，实际上如果你在传入参数的时候，在MyBatis里面也是会把它封装成一个Map的，map的key就是参数名，所以这个时候collection属性值就是传入的List或array对象在自己封装的map里面的key

	<select id="dynamicForeachTest" resultType="Blog">
		select * from t_blog where id in
		<foreach collection="list" index="index" item="item" open="(" separator="," close=")">
			#{item}
		</foreach>
	</select>

public List<Blog> dynamicForeachTest(List<Integer> ids);

	@Test
	public void dynamicForeachTest() {
		SqlSession session = Util.getSqlSessionFactory().openSession();
		BlogMapper blogMapper = session.getMapper(BlogMapper.class);
		List<Integer> ids = new ArrayList<Integer>();
		ids.add(1);
		ids.add(3);
		ids.add(6);
		List<Blog> blogs = blogMapper.dynamicForeachTest(ids);
		for (Blog blog : blogs)
			System.out.println(blog);
		session.close();
	}

	<select id="dynamicForeach2Test" resultType="Blog">
		select * from t_blog where id in
		<foreach collection="array" index="index" item="item" open="(" separator="," close=")">
			#{item}
		</foreach>
	</select>

public List<Blog> dynamicForeach2Test(int[] ids);

	@Test
	public void dynamicForeach2Test() {
		SqlSession session = Util.getSqlSessionFactory().openSession();
		BlogMapper blogMapper = session.getMapper(BlogMapper.class);
		int[] ids = new int[] {1,3,6,9};
		List<Blog> blogs = blogMapper.dynamicForeach2Test(ids);
		for (Blog blog : blogs)
			System.out.println(blog);
		session.close();
	}

	<select id="dynamicForeach3Test" resultType="Blog">
		select * from t_blog where title like "%"#{title}"%" and id in
		<foreach collection="ids" index="index" item="item" open="(" separator="," close=")">
			#{item}
		</foreach>
	</select>

	@Test
	public void dynamicForeach3Test() {
		SqlSession session = Util.getSqlSessionFactory().openSession();
		BlogMapper blogMapper = session.getMapper(BlogMapper.class);
		final List<Integer> ids = new ArrayList<Integer>();
		ids.add(1);
		ids.add(2);
		ids.add(3);
		ids.add(6);
		ids.add(7);
		ids.add(9);
		Map<String, Object> params = new HashMap<String, Object>();
		params.put("ids", ids);
		params.put("title", "中国");
		List<Blog> blogs = blogMapper.dynamicForeach3Test(params);
		for (Blog blog : blogs)
			System.out.println(blog);
		session.close();
	}