如何避免ibatisN+1查询

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Java代码避免ibatisN+1查询
多方：  
public class Employ {  
private int id;  
private String enployName;  
private int salary;  
private Department department;  

public Employ() {  
}  

public int getId() {  
return id;  
}  

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

public String getEnployName() {  
return enployName;  
}  

public void setEnployName(String enployName) {  
this.enployName = enployName;  
}  

public int getSalary() {  
return salary;  
}  

public void setSalary(int salary) {  
this.salary = salary;  
}  

public Department getDepartment() {  
return department;  
}  

public void setDepartment(Department department) {  
this.department = department;  
}  
}  

一方：  
public class Department {  
private int did;  
private String departmentName;  
private Listemployees;  


public int getDid() {  
return did;  
}  

public void setDid(int did) {  
this.did = did;  
}  

public String getDepartmentName() {  
return departmentName;  
}  

public void setDepartmentName(String departmentName) {  
this.departmentName = departmentName;  
}  

public ListgetEmployees() {  
return employees;  
}  

public void setEmployees(Listemployees) {  
this.employees = employees;  
}  
} 

多方：
public class Employ {
private int id;
private String enployName;
private int salary;
private Department department;

public Employ() {
}

public int getId() {
return id;
}

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

public String getEnployName() {
return enployName;
}

public void setEnployName(String enployName) {
this.enployName = enployName;
}

public int getSalary() {
return salary;
}

public void setSalary(int salary) {
this.salary = salary;
}

public Department getDepartment() {
return department;
}

public void setDepartment(Department department) {
this.department = department;
}
}

一方：
public class Department {
private int did;
private String departmentName;
private Listemployees;

public int getDid() {
return did;
}

public void setDid(int did) {
this.did = did;
}

public String getDepartmentName() {
return departmentName;
}

public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}

public ListgetEmployees() {
return employees;
}

public void setEmployees(Listemployees) {
this.employees = employees;
}
} 

如果您在映射文件的工作中想要避免ibatisN+1查询，您可以参考如下代码。

Xml代码避免ibatisN+1查询
多方：  
 
1. ＜?xml version="1.0" encoding="UTF-8" ?＞ 
2.  
3. ＜!DOCTYPE sqlMap       
4.     PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"       
5.     "http://ibatis.apache.org/dtd/sql-map-2.dtd"＞ 
6.  
7. ＜sqlMap namespace="Employ"＞ 
8.  
9.   ＜!-- Use type aliases to avoid typing the full classname every time. --＞ 
10.   ＜typeAlias alias="Employ" type="com.test.domain.Employ"/＞ 
11.  
12.   ＜!-- Result maps describe the mapping between the columns returned  
13.        from a query, and the class properties.  A result map isn't  
14.        necessary if the columns (or aliases) match to the properties  
15.        exactly. --＞ 
16.   ＜resultMap id="EmployResult" class="Employ"＞ 
17.     ＜result property="id" column="id"/＞ 
18.     ＜result property="enployName" column="employ_name"/＞ 
19.     ＜result property="salary" column="salary"/＞ 
20.     ＜result property="department.did" column="did"/＞ 
21.     ＜result property="department.departmentName" column="department_name"/＞ 
22.   ＜/resultMap＞ 
23.  
24.   ＜!-- Select with no parameters using the result map for Account class. --＞ 
25.   ＜select id="selectAllEmploy" resultMap="EmployResult"＞ 
26.   ＜![CDATA[ 
27.   select * from employees e, departments d where e.departmentid = d.did 
28.   ]]＞ 
29.   ＜/select＞ 
30.   ＜!-- A simpler select example without the result map.  Note the  
31.        aliases to match the properties of the target result class. --＞ 
32.     
33.   ＜!-- Insert example, using the Account parameter class --＞ 
34.   ＜insert id="insertEmploy" parameterClass="Employ"＞ 
35.   ＜![CDATA[ 
36.   insert into employees (employ_name, salary, departmentid) values(#enployName#, #salary#, #department.did#) 
37.   ]]＞ 
38.   ＜/insert＞ 
39.  
40.   ＜!-- Update example, using the Account parameter class --＞ 
41.  
42.   ＜!-- Delete example, using an integer as the parameter class --＞ 
43. ＜/sqlMap＞ 

一方：  
1. ＜?xml version="1.0" encoding="UTF-8" ?＞ 
2.  
3. ＜!DOCTYPE sqlMap       
4.     PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"       
5.     "http://ibatis.apache.org/dtd/sql-map-2.dtd"＞ 
6.  
7. ＜sqlMap namespace="Department"＞ 
8.  
9.   ＜!-- Use type aliases to avoid typing the full classname every time. --＞ 
10.   ＜typeAlias alias="Department" type="com.test.domain.Department"/＞ 
11.  
12.   ＜!-- Result maps describe the mapping between the columns returned  
13.        from a query, and the class properties.  A result map isn't  
14.        necessary if the columns (or aliases) match to the properties  
15.        exactly. --＞ 
16.   ＜resultMap id="DepartmentResult" class="Department"＞ 
17.     ＜result property="did" column="did"/＞ 
18.     ＜result property="departmentName" column="department_name"/＞ 
19.   ＜/resultMap＞ 
20.  
21.   ＜!-- Select with no parameters using the result map for Account class. --＞ 
22.   ＜select id="selectDepartmentById" parameterClass="int" resultMap="DepartmentResult"＞ 
23.   ＜![CDATA[ 
24.   select * from departments where did = #did# 
25.   ]]＞ 
26.   ＜/select＞ 
27.   ＜!-- A simpler select example without the result map.  Note the  
28.        aliases to match the properties of the target result class. --＞ 
29.     
30.   ＜!-- Insert example, using the Account parameter class --＞ 
31.   ＜insert id="insertDepartment" parameterClass="Department"＞ 
32.   ＜![CDATA[ 
33.   insert into departments (department_name) values(#departmentName#) 
34.   ]]＞ 
35.   ＜/insert＞ 
36.  
37.   ＜!-- Update example, using the Account parameter class --＞ 
38.  
39.   ＜!-- Delete example, using an integer as the parameter class --＞ 
40. ＜/sqlMap＞

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