foreach kincolle’s blogs

The foreach is always used in the in contition. In the foreach there has 5 elements: item, index, collection, open, separator and close.

• item: define the name of element which will be iterated
• index: define the name of positoin where the iteration it is
• open: what will be started with
• separator: what symbol will be used for separation
• close: what will be end with

There are 3 types of collection when use in:

1. The collection is a list
2. The collection is an array
3. The collection is a map

Here we have a mapper which the collection is a list.

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

The interface is：

public List dynamicForeachTest(List ids); 

Then the test code is:

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

Here we have a mapper which the collection is an array.

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

The interface is：

public List dynamicForeach2Test(int[] ids); 

Then the test code is:

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

Here we have a mapper which the collection is a map.

<select id="dynamicForeach3Test" parameterType="java.util.HashMap" 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>

The interface is：

public List dynamicForeach3Test(Map params); 

Then the test code is:

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