如何避免ibatisN+1查詢

這篇文章將為大家詳細講解有關如何避免ibatisN+1查詢，小編覺得挺實用的，因此分享給大家做個參考，希望大家閱讀完這篇文章后可以有所收獲。

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Java代碼避免ibatisN+1查詢
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查詢，您可以參考如下代碼。

Xml代碼避免ibatisN+1查詢
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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