hibernate多对多单向连接表关联

多对多单向连接表关联：只要一个端有Set就可以了，在<set>的属性中指明POJO中的Set集合，对应的链接表名，子元素<key>声明本端对应的连接表中的主键，<many-to-many>声明对应的连接表中的另一端的主键及其对应的POJO类.

以mis系统中的role(角色)和action(权限)表为例:
一个Role可以有多个Action, 一个Action也可以对应多个Role;
POJO如下:

package mis.hibernate.model;

import java.util.HashSet;
import java.util.Set;


/**
 * Role entity. @author MyEclipse Persistence Tools
 */

public class Role  implements java.io.Serializable {

    private static final long serialVersionUID = 7198786374572086190L;
	
    private Integer id;
    private String name;
    private String note;
    private Integer flag;
    private Integer version;
    private Set actions = new HashSet(0);


    // Constructors

    /** default constructor */
    public Role() {
    }

	/** minimal constructor */
    public Role(String name) {
        this.name = name;
    }
    
    /** full constructor */
    public Role(String name, String note, Integer flag, Integer version, Set actions) {
        this.name = name;
        this.note = note;
        this.flag = flag;
        this.version = version;
        this.actions = actions;
    }

   
    // Property accessors

    public Integer getId() {
        return this.id;
    }
    
    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return this.name;
    }
    
    public void setName(String name) {
        this.name = name;
    }

    public String getNote() {
        return this.note;
    }
    
    public void setNote(String note) {
        this.note = note;
    }

    public Integer getFlag() {
        return this.flag;
    }
    
    public void setFlag(Integer flag) {
        this.flag = flag;
    }

    public Integer getVersion() {
        return this.version;
    }
    
    public void setVersion(Integer version) {
        this.version = version;
    }

    public Set getActions() {
        return this.actions;
    }
    
    public void setActions(Set actions) {
        this.actions = actions;
    }
}

package mis.hibernate.model;

/**
 * Action entity.
 * 
 * @author MyEclipse Persistence Tools
 */

public class Action implements java.io.Serializable {

	// Fields

	private Integer id;
	private String name;
	private String displayName;
	private String description;
	private Integer parentId;
	private String url;
	private Integer flag;
	private Integer version;

	// Constructors

	/** default constructor */
	public Action() {
	}

	/** minimal constructor */
	public Action(String name) {
		this.name = name;
	}

	/** full constructor */
	public Action(String name, String displayName, String description,
			Integer parentId, String url, Integer flag, Integer version) {
		this.name = name;
		this.displayName = displayName;
		this.description = description;
		this.parentId = parentId;
		this.url = url;
		this.flag = flag;
		this.version = version;
	}

	// Property accessors

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getDisplayName() {
		return this.displayName;
	}

	public void setDisplayName(String displayName) {
		this.displayName = displayName;
	}

	public String getDescription() {
		return this.description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public Integer getParentId() {
		return this.parentId;
	}

	public void setParentId(Integer parentId) {
		this.parentId = parentId;
	}

	public String getUrl() {
		return this.url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public Integer getFlag() {
		return this.flag;
	}

	public void setFlag(Integer flag) {
		this.flag = flag;
	}

	public Integer getVersion() {
		return this.version;
	}

	public void setVersion(Integer version) {
		this.version = version;
	}

}

hbm.xml如下：

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="mis.hibernate.model.Role" table="role" catalog="mis2009">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="identity" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" length="128" not-null="true" unique="true">
                <comment>权限组名称</comment>
            </column>
        </property>
        <property name="note" type="java.lang.String">
            <column name="note" length="128">
                <comment>备注</comment>
            </column>
        </property>
        <property name="flag" type="java.lang.Integer">
            <column name="flag">
                <comment>标识</comment>
            </column>
        </property>
        <property name="version" type="java.lang.Integer">
            <column name="version">
                <comment>版本号</comment>
            </column>
        </property>
        <set name="actions" table="role_action">
        	<key column="roleId"></key>
        	<many-to-many column="actionId" class="mis.hibernate.model.Action">
        	</many-to-many>
        </set>
    </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="mis.hibernate.model.Action" table="action" catalog="mis2009">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="identity" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" length="128" not-null="true" unique="true">
                <comment>权限名称</comment>
            </column>
        </property>
        <property name="displayName" type="java.lang.String">
            <column name="displayName" length="128">
                <comment>显示到界面的名称,用中文表示更直观</comment>
            </column>
        </property>
        <property name="description" type="java.lang.String">
            <column name="description" length="128">
                <comment>描述</comment>
            </column>
        </property>
        <property name="parentId" type="java.lang.Integer">
            <column name="parentId">
                <comment>父权限节点Id</comment>
            </column>
        </property>
        <property name="url" type="java.lang.String">
            <column name="url" length="128">
                <comment>对应的url地址</comment>
            </column>
        </property>
        <property name="flag" type="java.lang.Integer">
            <column name="flag">
                <comment>标识</comment>
            </column>
        </property>
        <property name="version" type="java.lang.Integer">
            <column name="version">
                <comment>版本号</comment>
            </column>
        </property>
    </class>
</hibernate-mapping>

hql查询语句:

select distinct action from Action action，Role role where action in elements(role.actions) and role.id=5